[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683

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Amaury Levé (Evangelink) merged 2 commits into
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged

[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba

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@EvangelinkAmaury Levé (Evangelink) commented May 29, 2026

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🤖 This is an automated contribution from Perf Improver.

Goal and Rationale

AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.

Approach

Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).

Performance Evidence

MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10

IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.

Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.

Trade-offs

  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.

Test Status

  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅

Reproducibility

./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests

Generated by Perf Improver · sonnet46 4.4M · ◷

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@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink) added area/performance Runtime / build performance / efficiency. type/automation Created or maintained by an agentic workflow. labels May 29, 2026
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Pull request overview

Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.

Changes:

  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.

Copilot's findings

  • Files reviewed: 1/1 changed files
  • Comments generated: 1

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
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Amaury Levé (Evangelink) commented May 29, 2026

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🔍 Build Failure Analysis

Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.

Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0

string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.

Affected file / errors (all CS1501):

FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)

Proposed fix

Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.

Example diff for all 9 affected lines:

- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs

🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f

Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷

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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs Outdated
@Evangelink
Amaury Levé (Evangelink) marked this pull request as ready for review May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This was referenced May 29, 2026
Closed
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@Evangelink
Amaury Levé (Evangelink) merged commit f59285e into mainMay 31, 2026
84 of 90 checks passed
@Evangelink
Amaury Levé (Evangelink) deleted the perf-assist/ansi-detector-no-regex-d3aa6641bab010ba branch May 31, 2026 06:45
This was referenced Jun 6, 2026
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
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Skip to content
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
Merged
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
Conversation
@Evangelink
@EvangelinkAmaury Levé (Evangelink)
commented
May 29, 2026

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🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
Add this agentic workflows to your repo
To install this agentic workflow, run
gh aw add githubnext/agentics/workflows/perf-improver.md@main

@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

area/performance
Runtime / build performance / efficiency.
type/automation
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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

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Amaury Levé (Evangelink)
commented
May 29, 2026

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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
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Amaury Levé (Evangelink)
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

@Evangelink
Amaury Levé (Evangelink)
marked this pull request as ready for review
May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced May 29, 2026

Closed


Closed

@Evangelink
Amaury Levé (Evangelink)
merged commit f59285e
into
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84 of 90 checks passed

@Evangelink
Amaury Levé (Evangelink)
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba

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This was referenced Jun 6, 2026

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, 'i');
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injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
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try {
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var __re = new RegExp('^' + ".*" + '

Skip to content
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
Merged
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
Conversation
@Evangelink
@EvangelinkAmaury Levé (Evangelink)
commented
May 29, 2026

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Member
🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
Add this agentic workflows to your repo
To install this agentic workflow, run
gh aw add githubnext/agentics/workflows/perf-improver.md@main

@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

area/performance
Runtime / build performance / efficiency.
type/automation
Created or maintained by an agentic workflow.
labels
May 29, 2026
CopilotAI
reviewed
May 29, 2026
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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

@Evangelink
Amaury Levé (Evangelink)
commented
May 29, 2026

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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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@Evangelink
Amaury Levé (Evangelink)
marked this pull request as ready for review
May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced May 29, 2026

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Amaury Levé (Evangelink)
merged commit f59285e
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mainMay 31, 2026

84 of 90 checks passed

@Evangelink
Amaury Levé (Evangelink)
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba

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This was referenced Jun 6, 2026

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
Merged
Amaury Levé (Evangelink) merged 2 commits into
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
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@EvangelinkAmaury Levé (Evangelink)
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🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
Add this agentic workflows to your repo
To install this agentic workflow, run
gh aw add githubnext/agentics/workflows/perf-improver.md@main

@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

area/performance
Runtime / build performance / efficiency.
type/automation
Created or maintained by an agentic workflow.
labels
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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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May 29, 2026

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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
Evangelink
Amaury Levé (Evangelink)
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

@Evangelink
Amaury Levé (Evangelink)
marked this pull request as ready for review
May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced May 29, 2026

Closed


Closed

@Evangelink
Amaury Levé (Evangelink)
merged commit f59285e
into
mainMay 31, 2026

84 of 90 checks passed

@Evangelink
Amaury Levé (Evangelink)
deleted the

perf-assist/ansi-detector-no-regex-d3aa6641bab010ba

branch
May 31, 2026 06:45

This was referenced Jun 6, 2026

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
Merged
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
Conversation
@Evangelink
@EvangelinkAmaury Levé (Evangelink)
commented
May 29, 2026

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🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
Add this agentic workflows to your repo
To install this agentic workflow, run
gh aw add githubnext/agentics/workflows/perf-improver.md@main

@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

area/performance
Runtime / build performance / efficiency.
type/automation
Created or maintained by an agentic workflow.
labels
May 29, 2026
CopilotAI
reviewed
May 29, 2026
View reviewed changes
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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

@Evangelink
Amaury Levé (Evangelink)
commented
May 29, 2026

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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
Evangelink
Amaury Levé (Evangelink)
commented
May 29, 2026
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
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Amaury Levé (Evangelink) merged 2 commits into
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
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@EvangelinkAmaury Levé (Evangelink)
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🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
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@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Amaury Levé (Evangelink)
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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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@Evangelink
Amaury Levé (Evangelink)
marked this pull request as ready for review
May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced May 29, 2026

Closed


Closed

@Evangelink
Amaury Levé (Evangelink)
merged commit f59285e
into
mainMay 31, 2026

84 of 90 checks passed

@Evangelink
Amaury Levé (Evangelink)
deleted the

perf-assist/ansi-detector-no-regex-d3aa6641bab010ba

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This was referenced Jun 6, 2026

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
Merged
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
Merged
[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
mainfrom 
perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
Conversation
@Evangelink
@EvangelinkAmaury Levé (Evangelink)
commented
May 29, 2026

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🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
Add this agentic workflows to your repo
To install this agentic workflow, run
gh aw add githubnext/agentics/workflows/perf-improver.md@main

@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

area/performance
Runtime / build performance / efficiency.
type/automation
Created or maintained by an agentic workflow.
labels
May 29, 2026
CopilotAI
reviewed
May 29, 2026
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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Amaury Levé (Evangelink)
commented
May 29, 2026

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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
Evangelink
Amaury Levé (Evangelink)
commented
May 29, 2026
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
Outdated

Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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@Evangelink
Amaury Levé (Evangelink)
marked this pull request as ready for review
May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced May 29, 2026

Closed


Closed

@Evangelink
Amaury Levé (Evangelink)
merged commit f59285e
into
mainMay 31, 2026

84 of 90 checks passed

@Evangelink
Amaury Levé (Evangelink)
deleted the

perf-assist/ansi-detector-no-regex-d3aa6641bab010ba

branch
May 31, 2026 06:45

This was referenced Jun 6, 2026

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons - #8683
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Amaury Levé (Evangelink) merged 2 commits into
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
May 31, 2026
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[perf-improver] perf: replace Regex array in AnsiDetector with direct string comparisons#8683
Amaury Levé (Evangelink) merged 2 commits into
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perf-assist/ansi-detector-no-regex-d3aa6641bab010ba
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@EvangelinkAmaury Levé (Evangelink)
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🤖 This is an automated contribution from Perf Improver.
Goal and Rationale
AnsiDetector held a static readonly Regex[] TerminalsRegexes field initialised with 17 new Regex(...) instances. These were allocated (and in some runtimes compiled) at class-initialisation time, purely to perform very simple prefix/substring checks against a terminal-type string. Every pattern maps directly to a StartsWith or Contains call, so no regex engine is needed.
Approach
Replace the Regex[] field and its .Any(regex => regex.IsMatch(...)) loop with a single bool expression chaining string.StartsWith / string.Contains (all with StringComparison.Ordinal), preserving each original pattern's semantics exactly — including the negative-lookahead case (^(?!eterm-color).*eterm.* → Contains("eterm") && !StartsWith("eterm-color")).
Performance Evidence
MetricBeforeAfter
Regex instances allocated at startup170
Regex compilation workyes (interpreted mode)eliminated
Regex[] array allocation10
IsAnsiSupported is called once per process (from NativeMethods) so this is a startup-cost win. The method now allocates nothing and executes with pure string comparison instructions.
Methodology: code inspection + BenchmarkDotNet would show reduced allocations on first call; the key claim (17 fewer allocations) is directly verifiable from the diff.
Trade-offs
  • Slightly more verbose than the regex array, but each line has a comment mapping it back to the original regex.
  • No behavioral change — all 17 patterns are preserved faithfully.
Test Status
  • Microsoft.Testing.Platform.UnitTests (net8.0): 992 passed, 0 failed, 3 skipped ✅
Reproducibility
./build.sh # restore + build
artifacts/bin/Microsoft.Testing.Platform.UnitTests/Debug/net8.0/Microsoft.Testing.Platform.UnitTests
Generated by Perf Improver · sonnet46 4.4M · ◷
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@Evangelink
perf: replace Regex array in AnsiDetector with direct string comparisons
bc95b9f
Eliminates 17 Regex object allocations and their compilation cost by
replacing regex patterns with equivalent StartsWith/Contains string
operations. The terminal-type detection patterns are all simple
prefix/substring checks that don't need regex.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
May 29, 2026 14:46
@EvangelinkAmaury Levé (Evangelink)
added

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Pull request overview
Replaces a static readonly Regex[] of 17 patterns in AnsiDetector.IsAnsiSupported with a chain of StartsWith/Contains calls (all StringComparison.Ordinal) to remove the regex allocations/compilation that happen at class init for what are effectively prefix/substring checks.
Changes:
  • Remove TerminalsRegexes array and .Any(regex => regex.IsMatch(...)) loop.
  • Inline 17 equivalent string comparisons, including the negative-lookahead case for eterm vs eterm-color.
Show a summary per file
FileDescription
src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.csReplaces the regex array with a chained StartsWith/Contains expression.
Copilot's findings
  • Files reviewed: 1/1 changed files
  • Comments generated: 1
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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🔍 Build Failure Analysis
Summary — The netstandard2.0 build of Microsoft.Testing.Platform fails because string.Contains(string, StringComparison) does not exist in that target framework.
Root cause: string.Contains(string, StringComparison) unavailable on netstandard2.0
string.Contains(string, StringComparison) was introduced in .NET Standard 2.1 / .NET Core 2.1. The project targets netstandard2.0 (among others), which only has string.Contains(string) (no StringComparison overload). The PR replaced Regex-based matching with plain string operations — a good optimization — but the 9 calls to .Contains(..., StringComparison.Ordinal) break the netstandard2.0 compilation.
Affected file / errors (all CS1501):
FileLineCall
AnsiDetector.cs:2626termType.Contains("eterm", StringComparison.Ordinal)
AnsiDetector.cs:2929termType.Contains("tmux", StringComparison.Ordinal)
AnsiDetector.cs:3434termType.Contains("ansi", StringComparison.Ordinal)
AnsiDetector.cs:3535termType.Contains("scoansi", StringComparison.Ordinal)
AnsiDetector.cs:3636termType.Contains("cygwin", StringComparison.Ordinal)
AnsiDetector.cs:3737termType.Contains("linux", StringComparison.Ordinal)
AnsiDetector.cs:3838termType.Contains("konsole", StringComparison.Ordinal)
AnsiDetector.cs:3939termType.Contains("bvterm", StringComparison.Ordinal)
AnsiDetector.cs:4141termType.Contains("alacritty", StringComparison.Ordinal)
Proposed fix
Replace every termType.Contains(value, StringComparison.Ordinal) with termType.IndexOf(value, StringComparison.Ordinal) >= 0. string.IndexOf(string, StringComparison) is available in netstandard2.0. The StartsWith calls are fine — that overload exists on netstandard2.0.
Example diff for all 9 affected lines:
- || (termType.Contains("eterm", StringComparison.Ordinal)+ || (termType.IndexOf("eterm", StringComparison.Ordinal) >= 0- || termType.Contains("tmux", StringComparison.Ordinal)+ || termType.IndexOf("tmux", StringComparison.Ordinal) >= 0- || termType.Contains("ansi", StringComparison.Ordinal)+ || termType.IndexOf("ansi", StringComparison.Ordinal) >= 0- || termType.Contains("scoansi", StringComparison.Ordinal)+ || termType.IndexOf("scoansi", StringComparison.Ordinal) >= 0- || termType.Contains("cygwin", StringComparison.Ordinal)+ || termType.IndexOf("cygwin", StringComparison.Ordinal) >= 0- || termType.Contains("linux", StringComparison.Ordinal)+ || termType.IndexOf("linux", StringComparison.Ordinal) >= 0- || termType.Contains("konsole", StringComparison.Ordinal)+ || termType.IndexOf("konsole", StringComparison.Ordinal) >= 0- || termType.Contains("bvterm", StringComparison.Ordinal)+ || termType.IndexOf("bvterm", StringComparison.Ordinal) >= 0- || termType.Contains("alacritty", StringComparison.Ordinal);+ || termType.IndexOf("alacritty", StringComparison.Ordinal) >= 0;
Build overview
  • Project: Microsoft.Testing.Platform.csproj
  • Target framework: netstandard2.0
  • Error: CS1501 — No overload for method 'Contains' takes 2 arguments (9 occurrences)
  • File: src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
🤖 Generated by the Build Failure Analysis workflow · commit bc95b9f
Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M · ◷
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Generated by Build Failure Analysis for issue #8683 · sonnet46 2.3M
Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Comment threadsrc/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiDetector.cs
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Amaury Levé (Evangelink)
marked this pull request as ready for review
May 29, 2026 16:50
@Evangelink
Fix netstandard2.0 build: use IndexOf instead of Contains(string, Str…
60af47e
…ingComparison)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Amaury Levé (Evangelink)
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