Expand the CSC problem matcher to light up more errors on GitHub.

[StephenCleary]

Description:

This extends the csc problem matcher to support more flexible error message syntax, with tests. All examples have been seen in actual GHA runner output (these are anonymized real-world cases).

There are three changes to the regex:

• At the beginning of the line, whitespace and msbuild-style project number prefixes (e.g., 10>) are allowed. This is necessary for dotnet msbuild error parsing as well as dotnet build error parsing in some scenarios.
• Column numbers are now captured.
• Error codes no longer need to end in a number. This is necessary for dotnet format error parsing.

Related issue:

Replaces #691. Also see #583 which takes the alternative approach of adding an independent problem matcher for dotnet format (this PR includes dotnet format errors in the csc problem matcher).

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[Copilot]

Pull request overview

This PR expands the GitHub Actions CSC problem matcher regex so it recognizes a wider variety of real-world compiler/analyzer error formats (including dotnet msbuild prefixes and dotnet format-style codes), and updates tests to cover the new parsing behavior.

Changes:

• Updated .github/csc.json regex to allow leading whitespace and optional MSBuild project-number prefixes (e.g., 20>), capture column numbers, and allow non-numeric error codes.
• Extended Jest coverage with multiple real-world-inspired matcher examples (including dotnet format and MSBuild-prefixed output).
• Refactored the test to use test.each for clearer case-by-case validation.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
__tests__/csc.test.ts	Adds multiple test cases validating the expanded matcher behavior and captured groups (including column).
.github/csc.json	Expands the matcher regex and updates capture-group mapping (adds column, shifts indices).

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[StephenCleary]

CC @baronfel

[baronfel]

LGTM from MSBuild team side!

[Frulfump]

Nice now we just have to wait for the maintainers of this repo and they are always super slow #701 and #560
One could clear the backlog of this repo in a week with AI but I think they are aiming for job security...

[StephenCleary]

@priya-kinthali Can you merge this?

[Falco20019]

Might also resolve #603 and superseed #605 finally after a year with no feedback.

[priya-kinthali]

Hello @StephenCleary👋,
Thanks for the expanded regex coverage and comprehensive test cases! At this point, we haven't seen enough community demand to prioritise this, but we'll consider exploring the possibility of incorporating these changes in a future update as we gather more community engagement and interest. Thanks again for your contribution!

[Falco20019]

@priya-kinthali I also requested it by #603 over a year ago and I also know some others using my branch for some time