gohugoio/hugo · error

npm pack: failed to open package file: %w

Error message

npm pack: failed to open package file: %w

What it means

While collecting package.json/package.hugo.json files from all mounted Hugo modules (walking the _jsconfig virtual folder), Hugo failed to open one of the discovered files via its filesystem metadata. This is an I/O failure on a file the walker just listed, so it usually indicates filesystem-level trouble rather than bad JSON.

Source

Thrown at modules/npm/package_builder.go:168

			return nil
		},
	})
	if err := w.Walk(); err != nil {
		return err
	}

	// Process collected entries: for each module, prefer package.hugo.json
	// over package.json at the root level. Workspace package.json files are always processed.
	for _, e := range entries {
		m := e.info.Meta()
		// Skip root-level package.json if this module has package.hugo.json.
		if !e.isHugoJSON && e.isRootLevel && modulesWithHugoJSON[m.ModulePath()] {
			continue
		}

		f, err := m.Open()
		if err != nil {
			return fmt.Errorf("npm pack: failed to open package file: %w", err)
		}
		b.Add(m.ModulePath(), f)
		f.Close()
	}

	if b.Err() != nil {
		return fmt.Errorf("npm pack: failed to build: %w", b.Err())
	}

	// 4. Build the autogenerated workspace package.json.
	// Exclude deps already defined by the project itself — they don't
	// need to be duplicated in the workspace and it simplifies maintenance.
	moduleDeps := make(map[string]any)
	moduleDepsComments := make(map[string]any)
	for k, v := range b.dependencies {
		if b.dependenciesComments[k] != "project" {
			moduleDeps[k] = v
			moduleDepsComments[k] = b.dependenciesComments[k]

View on GitHub ↗ (pinned to 8a468df065)

Solutions

1. Re-run `hugo mod npm pack` — transient races with npm installs or editors often clear on retry.
2. Check permissions on the reported module's package.json and on the Hugo module cache; run `hugo mod clean` to refresh cached modules.
3. If using vendoring, re-run `hugo mod vendor` so `_vendor` matches current module versions.
4. Look for broken symlinks in themes/modules that mount package.json.

for _, p := range packageFiles {
    if fi, err := os.Stat(p); err != nil || fi.IsDir() {
        return fmt.Errorf("package.hugo.json missing or unreadable: %s", p)
    }
}

if err := b.Build(); err != nil {
    if errors.Is(err, fs.ErrNotExist) || errors.Is(err, fs.ErrPermission) {
        log.Fatalf("check that package.hugo.json exists and is readable in each module: %v", err)
    }
    return err
}

When it happens

Trigger: `hugo mod npm pack` walking module-mounted package files where `m.Open()` fails — the underlying file was deleted/renamed between listing and open, permissions deny reading, or a broken symlink/vendored module path resolves to nothing.

Common situations: A concurrent process (npm install, editor, watcher) rewriting package.json during packing; stale `_vendor` directory after modules changed; permission problems in the module cache (`hugo mod clean` targets); network/overlay filesystems dropping files.

Related errors

• failed to vendor module: %w
• failed to copy module to vendor dir: %w
• failed to make target dir: %w
• failed to copy module file to vendor: %w
• failed to copy resources to vendor dir: %w

AI-assisted analysis of gohugoio/hugo@8a468df065 (2026-07-31). Data as JSON: /data/errors/e2921287b6b422ba.json. Report an issue: GitHub ↗.