[linter-miner] Add walkfuncerrshadow linter: detect err-shadowing in filepath.Walk callbacks

[github-actions]

Summary

Adds a new custom go/analysis linter, walkfuncerrshadow, that flags a specific filepath.Walk/filepath.WalkDir anti-pattern found repeatedly in this codebase:

err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
    if err != nil {
        return err
    }
    ...
})
return err

Here the callback's err parameter shadows the outer err variable that holds the Walk/WalkDir call's own return value. This is confusing to read (which err is being checked/returned at any point?) and is an easy trap when refactoring: code added after the closure that references err may silently use the wrong variable if the outer declaration is later changed from := to =, or vice versa.

Evidence

Scanning pkg/ and cmd/ (excluding _test.go files) found this exact pattern in at least 9 places, including:

• pkg/cli/logs_download.go:192, :505
• pkg/cli/compile_watch.go:82
• pkg/cli/trial_support.go:58
• pkg/cli/remove_command.go:222, :342, :370
• pkg/cli/dependency_graph.go:66
• pkg/cli/logs_metrics.go:187, :680

Running the new linter against the full ./pkg/... and ./cmd/... tree confirms it flags exactly these call sites and no false positives, while correctly ignoring filepath.Walk calls where the callback uses a distinct parameter name (e.g. walkErr) or where the outer variable is not named err.

Implementation

• New package pkg/linters/walkfuncerrshadow/ following the largefunc reference layout:
  • walkfuncerrshadow.go — the analyzer, using the shared nolint, filecheck, and astutil helper packages
  • walkfuncerrshadow_test.go — analysistest-based test
  • testdata/src/walkfuncerrshadow/walkfuncerrshadow.go — fixture covering flagged and non-flagged cases (Walk, WalkDir, distinct param name, distinct outer variable name)
• Registered in pkg/linters/registry.go (All()), and documented in pkg/linters/doc.go and pkg/linters/README.md to keep the doc-sync tests passing.

Testing

• go test ./pkg/linters/... — all pass, including the new package and the doc/spec consistency tests
• go build ./cmd/linters and ran the resulting binary against ./pkg/... ./cmd/... — confirms the 9 real occurrences above and no unexpected findings
• make fmt

---

Warning

Protected Files — Push Permission Denied

This was originally intended as a pull request, but the patch modifies protected files. A human must create the pull request manually.

Protected files

• README.md

The push was rejected because GitHub Actions does not have workflows permission to push these changes, and is never allowed to make such changes, or other authorization being used does not have this permission.

Create the pull request manually

# Download the patch from the workflow run
gh run download 30710875181 -n agent -D /tmp/agent-30710875181

# Create a new branch
git checkout -b linter-miner/walkfuncerrshadow-a4b0c9f03f201baf main

# Apply the patch (--3way handles cross-repo patches)
git am --3way /tmp/agent-30710875181/aw-linter-miner-walkfuncerrshadow.patch

# Push the branch and create the pull request
git push origin linter-miner/walkfuncerrshadow-a4b0c9f03f201baf
gh pr create --title '[linter-miner] Add walkfuncerrshadow linter: detect err-shadowing in filepath.Walk callbacks' --base main --head linter-miner/walkfuncerrshadow-a4b0c9f03f201baf --repo github/gh-aw

Generated by Linter Miner · auto · 120.8 AIC · ⌖ 10.4 AIC · ⊞ 7.7K · ◷

• expires on Aug 8, 2026, 9:55 AM UTC-08:00

[github-actions]

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