fix(golangci): detect major version and use correct output flag for v2

[bnema]

Summary

The golangci-lint wrapper injects --out-format=json to get structured output, but this flag was removed in golangci-lint v2. The wrapper now detects the installed major version and injects the correct flag.

What changed

The wrapper runs golangci-lint version before the actual lint invocation, parses the major version from the output, and selects the appropriate flag:

• v2+: --output.json.path=stdout
• v1: --out-format=json (existing behavior)

The user-supplied flag detection was also updated to recognise both v1 and v2 output flags, so the wrapper does not override them.

The version parsing logic is extracted into its own function with unit tests covering v1 output, v2 output, empty input, and garbage input. Three additional tests cover the flag detection for v1 flags, v2 flags, and no flags.

Related

Closes #596

References

• golangci-lint migration guide on --out-format removal
• golangci-lint v2 CLI docs for run command flags

[aeppling]

Hello bnema !

Thanks for contributing ,

PR #612 also fix this, we need to review both to know which one to take for this fix.

[aeppling]

After reviewing both this PR and #612 side-by-side, i'm in favor of #612 as the base for this fix because it addresses several additional issues that could cause problems:

1. v2 stdout mixing: golangci-lint v2 emits both its default text summary and JSON to stdout simultaneously when using
   --output.json.path=stdout. This means serde_json::from_str would fail on the mixed output. fix: golangci-lint v1/v2 compatibility and non-run subcommand passthrough #612 solves this by writing JSON to a temp file instead.

2. Subcommand passthrough: commands like rtk golangci-lint version or rtk golangci-lint linters currently break because run is always injected. fix: golangci-lint v1/v2 compatibility and non-run subcommand passthrough #612 detects non-run subcommands and passes them through.

3. Fallback direction: defaulting to v1 on detection failure re-introduces the original bug for v2 users (the exact scenario this PR tries to fix). fix: golangci-lint v1/v2 compatibility and non-run subcommand passthrough #612 defaults to v2, which is the safer direction since v1 is EOL.

That said, your v prefix handling (trim_start_matches('v')) is something #612 is missing and would need to adopt, we've flagged that there.

Your work directly contributed to catching that gap.