gastownhall/beads · error

cannot stat default.nix: %v

Error message

cannot stat default.nix: %v

What it means

fixNixHash repairs the vendorHash in default.nix by rewriting the file. The first step is os.Stat("default.nix") to capture the file's permissions for the later rewrite; if the file cannot be stat'ed (typically because it does not exist in the current working directory), this error wraps the underlying os error.

Source

Thrown at cmd/bd/preflight.go:755

	cmd2 := exec.Command("git", "diff", "--name-only", "--cached", "--", "go.sum")
	out2, _ := cmd2.Output()
	if len(strings.TrimSpace(string(out1))) == 0 && len(strings.TrimSpace(string(out2))) == 0 {
		return false, "", "", nil
	}

	if _, err := exec.LookPath("nix"); err != nil {
		return false, "", "", fmt.Errorf(
			"nix not found in PATH\n  Manual fix:\n" +
				"    1. Edit default.nix: set vendorHash = \"sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=\"\n" +
				"    2. Run: nix build .#default\n" +
				"    3. Copy the 'got:' hash from the error into default.nix",
		)
	}

	nixPath := "default.nix"
	nixInfo, err := os.Stat(nixPath)
	if err != nil {
		return false, "", "", fmt.Errorf("cannot stat default.nix: %v", err)
	}
	nixPerm := nixInfo.Mode().Perm()

	content, err := os.ReadFile(nixPath)
	if err != nil {
		return false, "", "", fmt.Errorf("cannot read default.nix: %v", err)
	}

	re := regexp.MustCompile(`(vendorHash\s*=\s*)"([^"]+)"`)
	loc := re.FindSubmatchIndex(content)
	if loc == nil {
		return false, "", "", fmt.Errorf("vendorHash not found in default.nix")
	}
	oldHash := string(content[loc[4]:loc[5]])

	const sentinel = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="
	probed := append(append([]byte{}, content[:loc[4]]...), append([]byte(sentinel), content[loc[5]:]...)...)
	if err := os.WriteFile(nixPath, probed, nixPerm); err != nil {

View on GitHub (pinned to 71377f2769)

Solutions

1. cd to the repository root (where default.nix lives) and re-run `bd fix`
2. Verify default.nix exists: `ls -la default.nix` — recreate or restore it from git if missing
3. Check directory permissions if the path exists but stat still fails

Example fix

// before
$ cd cmd/bd && bd fix
cannot stat default.nix: stat default.nix: no such file or directory
// after
$ cd /path/to/repo && bd fix

[ -f default.nix ] || { echo "run from repo root where default.nix lives"; exit 1; }

out, err := exec.Command("bd", "fix").CombinedOutput()
if err != nil && strings.Contains(string(out), "cannot stat default.nix") {
    // cd to repo root or restore default.nix, then retry
}

When it happens

Trigger: Running `bd fix` from a directory where default.nix does not exist (repo root expected), or where the path exists but is unreadable at the directory level (permissions), or a symlink pointing to nothing.

Common situations: Executing `bd fix` from a subdirectory instead of the repository root; a broken default.nix symlink; renamed/deleted default.nix after switching build systems.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• cannot read cmd/bd/version.go: %v
• reading reason file %q: %w
• parsing formula: %w
• loading formula %q: %w
• target repo %s is not initialized; refusing to initialize it

AI-assisted analysis of gastownhall/beads@71377f2769 (2026-08-30). Data as JSON: /api/errors/25804cdb244c2780. Report an issue: GitHub.