Fix CSS selector support for numeric IDs and escape sequences - #150

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sinpru:fix-finding-element-with-number
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Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
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sinpru:fix-finding-element-with-number

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

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@sinpru@aristotelos
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
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Fix CSS selector support for numeric IDs and escape sequences - #150

Open
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number
Open

Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number

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@sinpru

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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Author

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

2 participants

@sinpru@aristotelos
, 'i'); if (__m === '*' || __re.test(location.href)) { 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); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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Fix CSS selector support for numeric IDs and escape sequences - #150

Open
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number
Open

Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number

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@sinpru

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

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@sinpru@aristotelos
, '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('^' + ".*" + '
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Fix CSS selector support for numeric IDs and escape sequences - #150

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sinpru:fix-finding-element-with-number
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Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
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sinpru:fix-finding-element-with-number

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

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@sinpru@aristotelos
, '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" + '
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Fix CSS selector support for numeric IDs and escape sequences - #150

Open
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number
Open

Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

2 participants

@sinpru@aristotelos
, '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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Fix CSS selector support for numeric IDs and escape sequences - #150

Open
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number
Open

Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number

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@sinpru

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

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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('^' + ".*" + '
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Fix CSS selector support for numeric IDs and escape sequences - #150

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sinpru:fix-finding-element-with-number
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Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Successfully merging this pull request may close these issues.

Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

2 participants

@sinpru@aristotelos
, '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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Fix CSS selector support for numeric IDs and escape sequences - #150

Open
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number
Open

Fix CSS selector support for numeric IDs and escape sequences#150
sinpru wants to merge 1 commit into
FlaUI:mainfrom
sinpru:fix-finding-element-with-number

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Fixes#138


private (string strategy, string value) ParseCssSelector(string cssSelector)
{
if (cssSelector.StartsWith("#"))

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This is not sufficient to judge that it is a simple CSS ID selector. To be sure, shouldn't a regex be used that checks that the complete cssSelector string matches a simple ID selector? It may be that the user sends a compound selector instead, and we should have a proper error message in that case that this is not supported.

The same comment holds for all parses below. To check that a regex matches the string fully, start with ^ and end with $.

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Fixed!

@aristotelos

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Would it be possible to add a unit test to e.g. ConditionParser to check the case that is currently not working?

@sinpru

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Actually I found out that my approach to fixing the CSS selector inside the controller was a mistake. I've refactored this to handle CSS selector parsing in ConditionParser instead.

}

var nameMatch = Regex.Match(cssSelector, @"\*?\[name\s*=\s*""(.+?)""\]", RegexOptions.IgnoreCase);
var nameMatch = Regex.Match(cssSelector, @"^\*?\[name\s*=\s*""(.+?)""\]$", RegexOptions.IgnoreCase);

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Couldn't this still match [name="test"][class="test2"] because of the .+ expression? If so, I suggest [^""]+ instead. Please add a unit test to validate that [name="test"][class="test2"] throws as not supported.

@sinprusinpruJan 7, 2026

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You're right, the .+ is too greedy, I've added a unit test that validates compound selectors throws as intened.

{
element = await Wait.Until(() => startNode().FindFirstByXPath(findElementRequest.Value), element => element != null, session.ImplicitWaitTimeout);
}
else if (findElementRequest.Using == "css selector")

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I've had a closer look and it seems that the ConditionParser should already allow escaped characters too. Instead of adding another case here, can't we fix the ConditionParser regular expressions if they fail?

@@ -31,19 +29,24 @@ public class ConditionParser : IConditionParser
/// - Attribute equals attribute (e.g. `[name=value]`) not supported.

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Also update the comment above Unicode escape characters or escape characters in the attribute name are not supported. -> Escape characters in the attribute name are not supported.

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssIdSelectorRegex = new Regex(@"^#(?<name>(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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The \s? is needed to make the trailing space optional per CSS spec. Unicode escapes like \34 can be followed by an optional space (\34 b or \34b are both valid depending on context).

/// - Multiple selectors are not supported.
/// </summary>
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f]))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssClassSelectorRegex = new Regex(@"^\.(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

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This goes the same as the one above

/// - ~= or |= not supported.
/// </summary>
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f]))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f]))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
private static Regex SimpleCssAttributeSelectorRegex = new Regex(@"^\*?\[\s*(?<ident>-?(?<nmstart>[_a-z]|[\240-\377])(?<nmchar>[_a-z0-9-]|[\240-\377])*)\s*=\s*(?<string>(?<string1>""(?<string1value>([^\n\r\f\\""]|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)"")|(?<string2>'(?<string2value>([^\n\r\f\\']|(?<escape>\\[^\r\n\f0-9a-f])|(?<unicode>\\[0-9a-fA-F]{1,6}\s?))*)'))\s*\]$", RegexOptions.Compiled | RegexOptions.IgnoreCase);

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Shouldn't the \s? part be omitted here?

[Test]
public void ParseCondition_CssSelectorWithSimpleNumericId_ReturnsAutomationIdCondition()
{
var cssSelector = @"#\31 ";

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Isn't "#\31" without the trailing space a better example for this case?

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The trailing space is needed when the next character is a hex digit. Without it #\31b would be parsed as a 3-character escape (\31b) instead of \31 followed by b.

{
public class ConditionParserTests
{
[TestCase("[name=\"2\"]")]

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Why were the ParseCondition_ByCssAttributeName_ReturnsCondition test cases removed?

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The old test was removed because it was testing the same functionality now covered by ParseCondition_CssSelectorWithEscapedSpecialChars_ReturnsNameCondition. Should I keep both for coverage?

@aristotelos

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Please squash the commits in this merge request together.

E.g. with git rebase -i or with:

git reset main
git commit

@sinpru
sinpruforce-pushed the fix-finding-element-with-number branch from bbc21dd to 81ad120CompareJanuary 7, 2026 04:22
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Using Selenium.WebDriver's By.Id for finding elements fails when the ID starts with a numeral

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@sinpru@aristotelos