Function Test_WithContextRenderError

log/default_test.go:105–132

Test_WithContextRenderError locks in M8: a misconfigured context tag must not silently drop context — the failure should leave a visible marker in the log line so operators notice. The error message is also sanitized for control bytes so a tag that wraps attacker-controlled data in its error cannot

(t *testing.T)

// because under -shuffle=on this test may run before any other log test, in
// which case the package-global logger.stdlog could still be nil.
func Test_WithContextRenderError(t *testing.T) {
	initDefaultLogger()
	t.Cleanup(initDefaultLogger)

	// Embed CR/LF in the error to exercise the sanitiser.
	templateErr := errors.New("tag\r\nboom")
	require.NoError(t, SetContextTemplate(ContextConfig{
		Format: "[${broken}] ",
		CustomTags: map[string]ContextTagFunc{
			"broken": func(_ Buffer, _ any, _ *ContextData, _ string) (int, error) {
				return 0, templateErr
			},
		},
	}))
	t.Cleanup(func() { MustSetContextTemplate(ContextConfig{}) })

	var w byteSliceWriter
	SetOutput(&w)

	WithContext(context.Background()).Info("payload")

	out := string(w.b)
	require.Contains(t, out, "ctx-render-error", "expected render-error marker, got %q", out)
	require.Contains(t, out, "payload", "expected payload to still be emitted, got %q", out)
	require.NotContains(t, out, "\r", "CR in error message must be sanitized")
	// One trailing newline from log.Output is expected; reject any embedded ones.
	require.Equal(t, 1, strings.Count(out, "\n"), "embedded LF in error message must be sanitized; got %q", out)
}

// Test_NewRetainedContext_TypedNil locks in the reflect-based nil detection
// in newRetainedContext: a typed-nil pointer wrapped in `any` must be treated