Add per-file comment markers to the postprocessing InputSig

The `--learn` support that follows needs to render inline-expectation
comments in the syntax of the file being edited, and a single CodeQL
database can mix source languages (e.g. Java plus XML), so the marker
must be chosen per file rather than per database.

Extend `TestPostProcessing::InputSig` with `getStartCommentMarker(relativePath)`
(no result -> that file is left untouched by `--learn`) and a defaulted
`getEndCommentMarker(relativePath)` (`none()` by default: line-comment
languages render no closing marker; block-comment languages can override
it later). Each language's `InlineExpectationsTestQuery.ql` implements
`getStartCommentMarker`, gated to that language's own source extensions so
that other file types (XML/YAML/HTML/ERB/Razor) extracted into the same
database are not rewritten with the wrong syntax.

This commit only wires the marker API through the signature and the
per-language inputs; nothing consumes it yet, so behavior is unchanged.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 1adfa307-c48e-43f5-94e3-8286e4a8c083

Author: d10c

actions/ql/lib/codeql/actions/test/internal/InlineExpectationsTestImpl.qll

@@ -21,4 +21,10 @@ module Impl implements InlineExpectationsTestSig {
           ":" + endColumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    relativePath.regexpMatch(".*\\.ya?ml") and
+    result = "#"
+  }
 }

actions/ql/test/utils/ActionsInlineExpectationsTestQuery.ql

@@ -20,6 +20,12 @@ private module Impl implements T::InlineExpectationsTestSig {
     )
   }
 
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    relativePath.regexpMatch(".*\\.ya?ml") and
+    result = "#"
+  }
+
   class ExpectationComment extends Yaml::YamlComment {
     string getContents() { result = this.getText() }
   }

cpp/ql/lib/utils/test/internal/InlineExpectationsTestImpl.qll

@@ -35,4 +35,13 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // C/C++ databases can also contain XML (e.g. `.xml`, `.props`), whose block-comment
+    // syntax is not yet supported, so we only render for C/C++ sources.
+    relativePath
+        .regexpMatch(".*\\.(c|cc|cpp|cxx|cp|c\\+\\+|h|hh|hpp|hxx|h\\+\\+|inl|tcc|ipp|tpp|cu|cuh)") and
+    result = "//"
+  }
 }

csharp/ql/lib/utils/test/internal/InlineExpectationsTestImpl.qll

@@ -59,4 +59,12 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // C# databases can also contain XML (e.g. `.csproj`, `.config`) and Razor markup, whose
+    // comment syntaxes are not yet supported, so we only render for C# sources.
+    relativePath.regexpMatch(".*\\.(cs|csx)") and
+    result = "//"
+  }
 }

go/ql/lib/utils/test/internal/InlineExpectationsTestImpl.qll

@@ -30,4 +30,12 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Go databases can also contain XML, whose block-comment syntax is not yet supported, so
+    // we only render for Go sources.
+    relativePath.matches("%.go") and
+    result = "//"
+  }
 }

java/ql/lib/utils/test/internal/InlineExpectationsTestImpl.qll

@@ -45,4 +45,12 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Java databases can also contain XML; those files use a different (block) comment
+    // syntax that is not yet supported, so we only render for Java and Kotlin sources.
+    relativePath.matches(["%.java", "%.kt"]) and
+    result = "//"
+  }
 }

java/ql/test-kotlin1/TestUtilities/internal/InlineExpectationsTestImpl.qll

@@ -42,4 +42,10 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    relativePath.matches(["%.java", "%.kt"]) and
+    result = "//"
+  }
 }

java/ql/test-kotlin2/TestUtilities/internal/InlineExpectationsTestImpl.qll

@@ -42,4 +42,10 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    relativePath.matches(["%.java", "%.kt"]) and
+    result = "//"
+  }
 }

javascript/ql/lib/utils/test/internal/InlineExpectationsTestImpl.qll

@@ -18,6 +18,14 @@ module Impl implements InlineExpectationsTestSig {
     )
   }
 
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // JavaScript databases can also contain HTML, whose block-comment syntax is not yet
+    // supported, so we only render for line-comment source files.
+    relativePath.regexpMatch(".*\\.(js|cjs|mjs|jsx|ts|cts|mts|tsx)") and
+    result = "//"
+  }
+
   abstract private class ExpectationCommentImpl extends Locatable {
     abstract string getContents();
 

python/ql/lib/utils/test/internal/InlineExpectationsTestImpl.qll

@@ -19,4 +19,12 @@ module Impl implements InlineExpectationsTestSig {
         f.getRelativePath() + ":" + startline + ":" + startcolumn + ":" + endline + ":" + endcolumn
     )
   }
+
+  bindingset[relativePath]
+  string getStartCommentMarker(string relativePath) {
+    // Python databases can also contain XML, whose block-comment syntax is not yet supported,
+    // so we only render for Python sources.
+    relativePath.regexpMatch(".*\\.(py|pyi)") and
+    result = "#"
+  }
 }