What Is a Problem Matcher?
A problem matcher is a registered pattern that the runner applies to a step's log output to extract file, line, and message fields from compiler or linter messages. Matched lines become structured annotations surfaced in the run summary. It bridges plain text tool output and the CI's native error display.
Why it matters
Without a problem matcher, a failing compile is just a wall of text a developer must read line by line. With one, the same errors appear as clickable annotations tied to exact files and lines. This makes failures far faster to diagnose without changing the underlying tool.
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