golang/go · error

internal error: MatchDirs: %s is not a valid filesystem patt

Error message

internal error: MatchDirs: %s is not a valid filesystem pattern

What it means

Internal error added to a Match via MatchDirs when the match's pattern is NOT a local/filesystem pattern (IsLocal() false). MatchDirs requires a pattern starting with an absolute path, './', or '../'; any other pattern reaching it indicates the dispatcher misrouted a non-local pattern to the filesystem matcher.

Source

Thrown at src/cmd/go/internal/search/search.go:289

		path = "/" + path
	}
	if !strings.HasSuffix(path, "/") {
		path += "/"
	}
	return path
}

// MatchDirs sets m.Dirs to a non-nil slice containing all directories that
// potentially match a local pattern. The pattern must begin with an absolute
// path, or "./", or "../". On Windows, the pattern may use slash or backslash
// separators or a mix of both.
//
// If any errors may have caused the set of directories to be incomplete,
// MatchDirs appends those errors to m.Errs.
func (m *Match) MatchDirs(modRoots []string) {
	m.Dirs = []string{}
	if !m.IsLocal() {
		m.AddError(fmt.Errorf("internal error: MatchDirs: %s is not a valid filesystem pattern", m.pattern))
		return
	}

	if m.IsLiteral() {
		m.Dirs = []string{m.pattern}
		return
	}

	// Clean the path and create a matching predicate.
	// filepath.Clean removes "./" prefixes (and ".\" on Windows). We need to
	// preserve these, since they are meaningful in MatchPattern and in
	// returned import paths.
	cleanPattern := filepath.Clean(m.pattern)
	isLocal := strings.HasPrefix(m.pattern, "./") || (os.PathSeparator == '\\' && strings.HasPrefix(m.pattern, `.\`))
	prefix := ""
	if cleanPattern != "." && isLocal {
		prefix = "./"
		cleanPattern = "." + string(os.PathSeparator) + cleanPattern

View on GitHub (pinned to b6b368adc5)

Solutions

1. Route non-local patterns to MatchPackages, keeping MatchDirs for local patterns.
2. Guard the dispatch with m.IsLocal() before calling MatchDirs.
3. Report as a Go toolchain bug if encountered via a normal 'go' command.

Example fix

// before
m := search.NewMatch("example.com/pkg")
m.MatchDirs(modRoots) // error: internal error: MatchDirs: example.com/pkg is not a valid filesystem pattern

// after
m := search.NewMatch("example.com/pkg")
m.MatchPackages() // correct matcher for non-local patterns

// Route by pattern locality before matching:
//   if m.IsLocal() { m.MatchDirs(modRoots) } else { m.MatchPackages() }

func matchCorrectly(m *search.Match, modRoots []string) {
    if m.IsLocal() {
        m.MatchDirs(modRoots)
    } else {
        m.MatchPackages()
    }
}

When it happens

Trigger: Calling search.Match.MatchDirs() on a Match whose pattern is an import-path pattern like 'example.com/pkg' or 'all' — the dispatcher that should have routed to MatchPackages misrouted instead.

Common situations: Only in tooling/tests that drive search.Match with the wrong matcher for a non-local pattern; not produced by standard CLI paths.

Related errors

• internal error: MatchPackages: %s is not a valid package pat
• internal error: main module version is not allowed: %w
• internal error: package %s is in the main module (%s), but v
• not in workspace mode but number of indexes is %v, not 1
• internal error: invalid binary cache entry: not a directory

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/b277c0b25bce86a0. Report an issue: GitHub.