linters: migrate osexitinlibrary, fprintlnsprintf, errstringmatch to type-based package identity

[Copilot]

Three CI-enforced linters identified stdlib package calls by syntactic identifier name (ident.Name == "os" etc.), creating alias-import false negatives and shadowing false positives. This migrates all three to astutil.IsPkgSelector, which resolves via pass.TypesInfo to a *types.PkgName and compares the imported path — the same pattern already applied to rawloginlib and sortslice.

Changes

• osexitinlibrary — removes the explicit ident extraction; delegates entirely to astutil.IsPkgSelector(pass, sel, "os")
• fprintlnsprintf — adds pass *analysis.Pass to isFmtFunc; replaces name comparison with astutil.IsPkgSelector(pass, sel, "fmt")
• errstringmatch — renames isStringsContains to brittleErrStringFuncName and extends coverage to Contains, HasPrefix, HasSuffix, EqualFold, Index, LastIndex, and Compare; uses astutil.IsPkgSelector(pass, sel, "strings") for type-resolved detection

Before (syntactic — misses aliases, fires on shadowed locals):

ident.Name == "os" && sel.Sel.Name == "Exit"

After (type-resolved):

astutil.IsPkgSelector(pass, sel, "os") && sel.Sel.Name == "Exit"

Testdata

Each linter gains two new cases:

• alias_import.go — aliased import (e.g. import xos "os") confirmed flagged (closes FN)
• Shadow case in main testdata — local variable named os/fmt/strings with matching method confirmed NOT flagged (closes FP)

errstringmatch testdata additionally covers the six new brittle string functions (HasPrefix, HasSuffix, EqualFold, Index, LastIndex, Compare) with both flagged and non-flagged cases.

[Copilot]

Pull request overview

This PR improves the correctness of three CI-enforced Go analyzers by switching stdlib package detection from syntactic identifier checks (prone to alias/import shadowing bugs) to type-based package identity via astutil.IsPkgSelector(pass, sel, "<import-path>"), aligning them with existing patterns in other linters.

Changes:

• Migrate osexitinlibrary, fprintlnsprintf, and errstringmatch to use astutil.IsPkgSelector for stdlib package resolution (fixes alias-import false negatives and shadowing false positives).
• Update helper signatures where needed (isFmtFunc, isStringsContains) to accept *analysis.Pass for TypesInfo-backed resolution.
• Add testdata covering both aliased imports (should be flagged) and local shadowing (should not be flagged), plus suggested-fix golden updates for fprintlnsprintf.

Show a summary per file

File	Description
pkg/linters/osexitinlibrary/osexitinlibrary.go	Switch os.Exit detection to astutil.IsPkgSelector to avoid alias/shadowing mis-detection.
pkg/linters/osexitinlibrary/testdata/src/osexitinlibrary/osexitinlibrary.go	Add a shadowing case to ensure local os variables aren’t flagged.
pkg/linters/osexitinlibrary/testdata/src/osexitinlibrary/alias_import.go	Add aliased import coverage to ensure xos.Exit is still flagged.
pkg/linters/fprintlnsprintf/fprintlnsprintf.go	Make isFmtFunc type-aware via pass and astutil.IsPkgSelector for robust fmt detection.
pkg/linters/fprintlnsprintf/testdata/src/fprintlnsprintf/fprintlnsprintf.go	Add a fmt-shadowing case to ensure local fmt variables aren’t flagged.
pkg/linters/fprintlnsprintf/testdata/src/fprintlnsprintf/fprintlnsprintf.go.golden	Mirror new shadowing scenario in the post-fix golden output.
pkg/linters/fprintlnsprintf/testdata/src/fprintlnsprintf/alias_import.go	Add aliased fmt import coverage to ensure the pattern is flagged and fixed.
pkg/linters/fprintlnsprintf/testdata/src/fprintlnsprintf/alias_import.go.golden	Expected output after suggested fix when fmt is aliased.
pkg/linters/errstringmatch/errstringmatch.go	Make strings.Contains detection type-aware via pass and astutil.IsPkgSelector.
pkg/linters/errstringmatch/testdata/src/errstringmatch/errstringmatch.go	Add a strings-shadowing case to ensure local strings variables aren’t flagged.
pkg/linters/errstringmatch/testdata/src/errstringmatch/alias_import.go	Add aliased import coverage to ensure str.Contains is still flagged.

Copilot's findings

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• Files reviewed: 11/11 changed files
• Comments generated: 0

[github-actions]

🧠 Matt Pocock Skills Reviewer has completed the skills-based review. ✅

[github-actions]

✅ Design Decision Gate 🏗️ completed the design decision gate check.

No ADR enforcement needed: PR #40247 does not have the 'implementation' label (has_implementation_label=false) and has 88 new lines of code in business logic directories, which is ≤100 (requires_adr_by_default_volume=false, no custom config).

[github-actions]

✅ Test Quality Sentinel completed test quality analysis.

No test files were added or modified in this PR. The PR modifies linter implementation files (osexitinlibrary.go, fprintlnsprintf.go, errstringmatch.go) and adds/updates testdata fixture files (alias_import.go, *.golden) used as analyzer inputs — none of these are *_test.go, *.test.cjs, or *.test.js files. Test Quality Sentinel skipped.

[github-actions]

✅ PR Code Quality Reviewer completed the code quality review.

[pelikhan]

@copilot run pr-finisher skill

[github-actions]

Skills-Based Review 🧠

Applied /tdd and /diagnose — approving with one minor inline suggestion.

📋 Key Themes & Highlights

Key Themes

• Correct root-cause fix: Moving from syntactic ident.Name == "os" comparisons to astutil.IsPkgSelector (type-resolved via pass.TypesInfo) is the right approach and already proven by rawloginlib and sortslice.
• Both failure modes tested: Each linter gets an alias_import.go fixture (closes the FN) and a shadow-variable case in the main testdata file (closes the FP). This is the complete set needed.
• Golden files correct: The fprintlnsprintf golden files correctly preserve the alias prefix (f.Fprintf not fmt.Fprintf) because buildFprintfFix only replaces the selector name, not the package qualifier — a subtle but important property that the new alias_import.go.golden directly validates.

Positive Highlights

• ✅ Net negative diff in implementation files (–20/+8): the fix simplifies the code, removing the intermediate ident extraction entirely.
• ✅ fprintlnsprintf has two call sites (Fprintln and Sprintf detection) that both needed updating — both are covered by a single alias-import test case.
• ✅ want annotations use correct regex escaping and the errstringmatch pattern correctly matches the prefix of the full diagnostic message.

Follow-up Opportunity (out of scope)

astutil.IsFmtErrorf in astutil.go already uses TypesInfo correctly (it was never broken), but its structure inlines the package+method check rather than composing IsPkgSelector. A small follow-up could simplify it to sel.Sel.Name == "Errorf" && IsPkgSelector(pass, sel, "fmt") for consistency.

🧠 Reviewed using Matt Pocock's skills by Matt Pocock Skills Reviewer · 104.9 AIC · ⌖ 7.77 AIC · ⊞ 6.9K

[github-actions]

[/tdd] The first parameter of Fprintln accepts interface{}, but fmt.Fprintln actually requires io.Writer. The shadow test still works correctly (any *os.File satisfies interface{}), but using io.Writer would more accurately model the real function signature. This also brings the stub in line with the codebase preference for any over interface{}.

[Copilot]

Fixed in the latest commit: updated fmtWriter.Fprintln to use io.Writer as the first parameter and any in place of interface{} throughout (both the source testdata and its golden file). Tests pass.

[github-actions]

@copilot review all comments and address unresolved review feedback.

Please resolve the outstanding review thread on the signature/type change.

Generated by 👨‍🍳 PR Sous Chef · 57 AIC · ⌖ 1.09 AIC · ⊞ 17.2K · ◷

[github-actions]

Please refresh the branch and rerun checks after the update.

Generated by 👨‍🍳 PR Sous Chef · 57 AIC · ⌖ 1.09 AIC · ⊞ 17.2K · ◷

[pelikhan]

@copilot merge main and recompile

[Copilot]

@copilot merge main and recompile

Done. Merged main and resolved conflicts in errstringmatch — the expanded brittle-functions set from main (HasPrefix, HasSuffix, EqualFold, Index, LastIndex, Compare) is now combined with the type-based IsPkgSelector detection from this PR. Ran make recompile (250/250 workflows compiled). Commit: $(git rev-parse --short HEAD).