Review of framework-test package

[wmdietl]

No description provided.

[Copilot]

Pull request overview

Small cleanup and bug-fix pass over the framework-test package: tightens collection construction, replaces Scanner with BufferedReader, removes a now-unused helper, and fixes a couple of latent correctness issues in diagnostic parsing and equality.

Changes:

• Replace Scanner-based file scanning with Files.newBufferedReader, and add a skip-test fast-path filter in TestUtilities.isJavaTestFile.
• Defensive-copy diagnosticFiles, mark processors unmodifiable in ImmutableTestConfiguration; simplify list mutation in TestConfigurationBuilder and drop the unused catListAndIterable helper; switch String.join("%n", ...) to System.lineSeparator().
• Fix TestDiagnosticUtils.fromPatternMatching to read from warningMatcher (not diagnosticMatcher) in the warning branch, and make TestDiagnostic.equals use this.getClass() so DetailedTestDiagnostic.equals (which delegates via super) actually works.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
framework-test/.../TypecheckResult.java	Build unexpectedDiagnostics directly from actualDiagnostics; wrap expected in a HashSet for removeAll.
framework-test/.../TypecheckExecutor.java	Use Collections.emptyList() instead of an empty ArrayList for the classes argument.
framework-test/.../TestUtilities.java	Switch Scanner to BufferedReader; add skip-test fast-path to short-circuit per-line checks.
framework-test/.../TestConfigurationBuilder.java	Inline list appends, drop catListAndIterable, and use System.lineSeparator() for joining error lines.
framework-test/.../SimpleOptionMap.java	Minor: drop redundant toAppend.length() argument to substring.
framework-test/.../PerDirectorySuite.java	Use real newlines in error message; construct ctor args array directly.
framework-test/.../ImmutableTestConfiguration.java	Defensive-copy diagnosticFiles; make processors an unmodifiable list.
framework-test/.../diagnostics/TestDiagnosticUtils.java	Read the linenogroup/lineno from warningMatcher and guard for patterns without that named group.
framework-test/.../diagnostics/TestDiagnostic.java	Use this.getClass() in equals so subclasses (e.g. DetailedTestDiagnostic) can be equal.
framework-test/.../CheckerFrameworkWPIPerDirectoryTest.java	Switch Scanner to BufferedReader in hasSkipComment.

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