Move `AddKeepAlives` trimmer step to post-trimming task by sbomer · Pull Request #10952 · dotnet/android

sbomer · 2026-03-16T18:13:57Z

Migrate AddKeepAlivesStep out of the ILLink custom step pipeline into a standalone MSBuild task that runs AfterTargets="ILLink", following the same pattern established by StripEmbeddedLibraries in #10894.

Core IL-rewriting logic is extracted into AddKeepAlivesHelper, shared by both the new task (trimmed builds) and the existing pipeline step (non-trimmed builds via LinkAssembliesNoShrink).

Migrate AddKeepAlivesStep out of the ILLink custom step pipeline into a standalone MSBuild task that runs AfterTargets="ILLink", following the same pattern established by StripEmbeddedLibraries in #10894. Core IL-rewriting logic is extracted into AddKeepAlivesHelper, shared by both the new task (trimmed builds) and the existing pipeline step (non-trimmed builds via LinkAssembliesNoShrink).

Replace DefaultAssemblyResolver with DirectoryAssemblyResolver (ReadWrite=true) to avoid file handle conflicts on Windows. The directory resolver caches all assemblies (both explicit and dependency-resolved), preventing duplicate file opens that caused IOException when the same assembly was opened as both a dependency and a primary target.

Replace standalone AddKeepAlives and StripEmbeddedLibraries MSBuild tasks with a single PostTrimmingPipeline task that opens assemblies once (via DirectoryAssemblyResolver with ReadWrite) and runs both modifications in a single pass. Extract StripEmbeddedLibrariesStep as an IAssemblyModifierPipelineStep for reuse.

…Step pattern Use List<IAssemblyModifierPipelineStep> with StripEmbeddedLibrariesStep and PostTrimmingAddKeepAlivesStep instead of calling helpers directly. Move the IsFrameworkAssembly check into StripEmbeddedLibrariesStep.ProcessAssembly and remove all outer-loop filtering so each step handles its own guards internally.

Copilot

Pull request overview

Moves the AddKeepAlives IL rewriting from an ILLink custom step into a post-ILLink MSBuild task, aligning with the earlier “post-trimming task” pattern and allowing the same KeepAlive injection to run for trimmed builds after ILLink.

Changes:

Introduces a new PostTrimmingPipeline MSBuild task that runs post-trimming assembly modifications (resource stripping + optional KeepAlive injection) in one pass.
Extracts KeepAlive IL-rewrite logic into AddKeepAlivesHelper and reuses it from both the existing non-trim pipeline and the new post-trim pipeline.
Removes the old StripEmbeddedLibraries task and drops AddKeepAlivesStep from the ILLink project/custom step registration.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj	Adds compilation of new linker helper/steps required by the new post-trim pipeline.
src/Xamarin.Android.Build.Tasks/Tasks/StripEmbeddedLibraries.cs	Removes the old standalone `StripEmbeddedLibraries` task implementation.
src/Xamarin.Android.Build.Tasks/Tasks/PostTrimmingPipeline.cs	Adds new post-ILLink task that opens assemblies read/write and applies post-trim modification steps.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.LlvmIr.targets	Switches from `StripEmbeddedLibraries` to `PostTrimmingPipeline` and removes ILLink custom-step registration for `AddKeepAlives`.
src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/StripEmbeddedLibrariesStep.cs	Adds pipeline step that strips embedded Android resource payloads from assemblies.
src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/PostTrimmingAddKeepAlivesStep.cs	Adds post-trimming pipeline step wrapper to call the shared KeepAlive helper.
src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/AddKeepAlivesStep.cs	Refactors to delegate logic to `AddKeepAlivesHelper` for the non-trim pipeline path.
src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/AddKeepAlivesHelper.cs	Adds shared IL-rewrite helper used by both non-trim and post-trim paths.
src/Microsoft.Android.Sdk.ILLink/Microsoft.Android.Sdk.ILLink.csproj	Stops compiling/linking `AddKeepAlivesStep` into the ILLink project.

sbomer · 2026-03-20T16:31:12Z

@copilot open a new pull request to apply changes based on the comments in this thread

Copilot · 2026-03-20T16:31:21Z

@sbomer I've opened a new pull request, #10981, to work on those changes. Once the pull request is ready, I'll request review from you.

…ated csproj comment Co-authored-by: sbomer <787361+sbomer@users.noreply.github.com>

…esolution attempts Co-authored-by: sbomer <787361+sbomer@users.noreply.github.com> Agent-Logs-Url: https://github.com/dotnet/android/sessions/399b2f01-0576-42f4-a1d4-d0f0d31f5eb7

Fix nullable Func delegate, whitespace, and csproj comment in PostTrimmingPipeline

…beddedLibrariesStep.cs Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

…esStep

sbomer · 2026-03-23T18:48:36Z

@jonathanpeppers this now moves the step to a separate post-trimming pipeline. #10891 might let us merge this with the existing assembly modification pipeline, but for now it is separate. PTAL!

jonathanpeppers

🤖 AI Review Summary

Verdict: ✅ LGTM

Found 0 issues.

Clean refactoring that extracts AddKeepAlives IL-rewriting logic from the ILLink custom step pipeline into a shared AddKeepAlivesHelper class, then runs it as a post-trimming MSBuild task via PostTrimmingPipeline. This follows the same pattern established by StripEmbeddedLibraries in #10894.

What I verified:

PostTrimmingPipeline extends AndroidTask, has TaskPrefix = "PTP", returns !Log.HasLoggedErrors ✅
[Required] property Assemblies has proper default = [] ✅
Non-required AddKeepAlives and Deterministic are value types (bool), no nullable issue ✅
Core IL-rewriting logic in AddKeepAlivesHelper is a pure extraction — no behavioral changes, same guards (HasTypeReference, IsDotNetAndroidAssembly) ✅
StripEmbeddedLibrariesStep correctly moved from the deleted StripEmbeddedLibraries task with logic preserved ✅
PostTrimmingAddKeepAlivesStep correctly documents that it skips the IsAndroidUserAssembly pre-filter (matching original ILLink behavior) ✅
Corlib resolution is properly memoized in the lambda closure ✅
Target renamed from _StripEmbeddedLibraries to _PostTrimmingPipeline with AfterTargets="ILLink" — same ordering ✅
AddKeepAlivesStep in the ILLink _TrimmerCustomSteps list is correctly removed ✅
All CI checks pass ✅

👍 Nice consolidation — running both steps in a single pass over assemblies with one assembly open/write cycle is a good efficiency improvement.

Review generated by android-reviewer from review guidelines.

jonathanpeppers reviewed Mar 16, 2026
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Comment threadsrc/Xamarin.Android.Build.Tasks/Tasks/AddKeepAlives.cs Outdated

Fix missing using directive in AddKeepAlivesHelper.cs
e24ddc3

sbomer self-assigned this Mar 18, 2026

sbomer added 3 commits March 18, 2026 16:19

sbomer mentioned this pull request Mar 19, 2026
Migrate AddKeepAlivesStep from ILLink custom step #10837
Closed

sbomer marked this pull request as ready for review March 20, 2026 16:21

sbomer requested review from grendello and simonrozsival as code owners March 20, 2026 16:21

Merge branch 'main' into dev/sbomer/addkeepalives-inner
acf4b70

CopilotAI review requested due to automatic review settings March 20, 2026 16:21

Copilotstarted reviewing on behalf of sbomer March 20, 2026 16:22 View session

CopilotAI reviewed Mar 20, 2026
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Initial plan
e8a2b8e

CopilotAI mentioned this pull request Mar 20, 2026
Fix nullable Func delegate, whitespace, and csproj comment in PostTrimmingPipeline #10981
Merged
2 tasks

CopilotAIand others added 5 commits March 20, 2026 17:05

Address copilot reviewer comments: nullable Func, whitespace fix, upd…
8215697
…ated csproj comment Co-authored-by: sbomer <787361+sbomer@users.noreply.github.com>

Memoize corlib resolution in PostTrimmingPipeline to avoid repeated r…
e6b2e5b
…esolution attempts Co-authored-by: sbomer <787361+sbomer@users.noreply.github.com> Agent-Logs-Url: https://github.com/dotnet/android/sessions/399b2f01-0576-42f4-a1d4-d0f0d31f5eb7

Merge pull request#10981from dotnet/copilot/sub-pr-10952
cfc21e1
Fix nullable Func delegate, whitespace, and csproj comment in PostTrimmingPipeline

Update src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/StripEm…
c033084
…beddedLibrariesStep.cs Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Restore missing 'using Xamarin.Android.Tasks' in StripEmbeddedLibrari…
3fa2b85
…esStep

sbomer changed the title ~~Move AddKeepAlives trimmer step to standalone MSBuild task~~Move AddKeepAlives trimmer step to post-trimming taskMar 23, 2026

sbomer requested a review from jonathanpeppers March 23, 2026 18:47

jonathanpeppers approved these changes Mar 23, 2026
View reviewed changes

jonathanpeppers merged commit 6b94e21 into mainMar 23, 2026
6 checks passed

jonathanpeppers deleted the dev/sbomer/addkeepalives-inner branch March 23, 2026 21:26

sbomer mentioned this pull request Mar 23, 2026
Migrate away from ILLink custom steps #10842
Open
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github-actionsBot locked and limited conversation to collaborators Apr 23, 2026

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Move `AddKeepAlives` trimmer step to post-trimming task - #10952

Move `AddKeepAlives` trimmer step to post-trimming task#10952
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