execcommandwithoutcontext precision: false positive on nil-guarded exec.Command fallback — autofix injects a nil context that pa [Content truncated due to length]

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Summary

The newly-landed execcommandwithoutcontext analyzer (24th custom linter) flags exec.Command calls that sit in the nil branch of an explicit ctx-nil guard, and its suggested autofix rewrites them to exec.CommandContext(ctx, ...). On that exact control-flow path ctx is provably nil, and the Go standard library's exec.CommandContext panics when given a nil context (panic("nil Context")). The diagnostic is a false positive and the autofix would introduce a runtime panic.

• Linter: pkg/linters/execcommandwithoutcontext (registered cmd/linters/main.go:52)
• Concrete false positive: pkg/workflow/github_cli.go:32
• Status: not yet CI-enforced, so it is not breaking builds today — but it blocks enforcement and the autofix is unsafe.

Root cause

run() reports any exec.Command whose enclosing FuncDecl/FuncLit has a named context.Context parameter, without inspecting the control flow guarding the call:

// pkg/linters/execcommandwithoutcontext/execcommandwithoutcontext.go
ctxParamName, hasCtx := contextParamName(pass, funcType)
if !hasCtx {
    continue
}
pass.Report(... "use exec.CommandContext(%s, ...)" ...) // no guard analysis

The analyzer correctly uses type identity for the package match (ObjectOf -> *types.PkgName -> Imported().Path() == "os/exec") and types.Identical for the ctx param, so this is not a syntactic-match issue — it is a missing control-flow guard check.

Concrete false positive

// pkg/workflow/github_cli.go:23
// When ctx is nil, it uses exec.Command; when ctx is provided, it uses exec.CommandContext.
func setupGHCommand(ctx context.Context, args ...string) *exec.Cmd {
    var cmd *exec.Cmd
    if ctx != nil {
        cmd = exec.CommandContext(ctx, "gh", args...)
    } else {
        cmd = exec.Command("gh", args...) // line 32 — FLAGGED, but ctx is nil here by construction
    }
    ...
}

This is the intentional dual-path shared implementation behind the public ExecGH (nil context) and ExecGHContext(ctx) wrappers — ExecGH even carries //nolint:staticcheck for exactly this reason. Applying the linter's suggested fix yields exec.CommandContext(ctx, "gh", args...) on the ctx == nil path, which panics at runtime.

Impact

• False positive on a legitimate, documented idiom (nil-context fallback APIs).
• Unsafe autofix: the suggested SuggestedFix would convert a working program into one that panics.
• Blocks enforcement: the linter cannot be added to CI (cgo.yml) while it mis-flags this site, and it currently has no internal/nolint support to suppress the warning (see companion enforce-readiness issue).

Recommendation

In run(), skip the exec.Command call when it is control-flow-guarded against the nil-context path. Two viable detection strategies (prefer the first, fall back to the second):

1. Guard-aware skip: walk the enclosing *ast.IfStmt chain; if the call is in the else of an if ctx != nil (or the then of an if ctx == nil) comparing the ctx parameter against nil, do not report.
2. Dual-path heuristic: if the same enclosing function already contains an exec.CommandContext(ctx, ...) call using that same ctx identifier, treat the function as an intentional dual-path implementation and skip.

Add testdata cases mirroring setupGHCommand (a // want-free if ctx != nil { CommandContext } else { Command } function) so the guarded fallback is covered.

Validation checklist

• execcommandwithoutcontext no longer reports pkg/workflow/github_cli.go:32.
• New testdata case: nil-guarded fallback (if ctx != nil {...} else { exec.Command(...) }) produces no diagnostic.
• Existing // want cases (BadRunCommand, method receiver, closure, func-lit) still fire.
• go test ./pkg/linters/execcommandwithoutcontext/... passes.

Effort: Small — single analyzer file (run() guard check) + testdata. Mirrors prior single-file precision fixes (sg29a1 #37492, sg30a2 #37741, sg31a2 #38029) that landed within ~1 day.

References: §27254549539

Generated by 🤖 Sergo - Serena Go Expert · 294.4 AIC · ⌖ 14.5 AIC · ⊞ 6.3K · ◷

• expires on Jun 16, 2026, 9:18 PM UTC-08:00

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🍪 Issue Monster selected this for Copilot

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If assignment succeeds, the Copilot coding agent will analyze the issue and create a pull request with the fix.

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This issue was automatically closed because it expired on 2026-06-17T05:18:58.828Z.

Closed by Workflow