kataras/iris · error

walk: walkFn: %w

Error message

walk: walkFn: %w

What it means

After gathering path info, the walker invokes the user-supplied walkFn for each file; any error the callback returns is wrapped as 'walk: walkFn: <err>'. This distinguishes errors originating in the consumer's per-file logic from filesystem traversal errors.

Source

Thrown at view/fs.go:45

			return fmt.Errorf("walk: %s: %w", path, err)
		}

		info, err := d.Info()
		if err != nil {
			if err != filepath.SkipDir {
				return fmt.Errorf("walk stat: %s: %w", path, err)
			}

			return nil
		}

		if info.IsDir() {
			return nil
		}

		walkFnErr := walkFn(path, info, err)
		if walkFnErr != nil {
			return fmt.Errorf("walk: walkFn: %w", walkFnErr)
		}

		return nil
	})

}

func asset(fileSystem fs.FS, name string) ([]byte, error) {
	data, err := fs.ReadFile(fileSystem, name)
	if err != nil {
		return nil, fmt.Errorf("asset: read file: %w", err)
	}

	return data, nil
}

func getFS(fsOrDir any) fs.FS {
	return context.ResolveFS(fsOrDir)

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Read the wrapped inner error to identify the failing file and cause.
2. Fix or remove the offending template file in the views tree.
3. Ensure template files have proper read permissions and valid content.
4. Retry the load if the failure was caused by concurrent file replacement.

Example fix

// before
templates/empty.html (0 bytes) -> walkFn error
// after
templates/empty.html populated with valid template content

return fs.WalkDir(fsys, root, func(p string, d fs.DirEntry, err error) error {
    if err != nil { return err }
    info, _ := d.Info()
    if !info.IsDir() {
        f, err := fsys.Open(p)
        if err != nil { return fmt.Errorf("preflight %s: %w", p, err) }
        f.Close()
    }
    return nil
})

if err := view.Register(engine); err != nil {
    if strings.Contains(err.Error(), "walk: walkFn:") {
        log.Fatalf("template processing failed: %v", err)
    }
    return err
}

When it happens

Trigger: The internal walkFn used when loading view templates returns an error for a file — e.g. reading the file failed, or a per-template parse/validation step inside walkFn errored — and that error propagates through the wrapper.

Common situations: A template file readable at list time but unreadable at read time, a zero-byte/corrupt template file, or a template path that conflicts with a registered engine's expected naming.

Related errors

• walk: %s: %w
• walk stat: %s: %w
• dest directory: %s: eval symlinks: %w
• unexpected "fsOrDir" argument type of %T (string or fs.FS or
• %s: %w

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/40bb2b0d083e27c2. Report an issue: GitHub.