What causes "error in writing codegen file: %w" in hasura/graphql-engine?

Check the wrapped OS error, then create the output directory: mkdir -p

error in writing codegen file: %w

Error message

error in writing codegen file: %w

What it means

Codegen received generated files from the extension but failed writing them to ActionConfig.Codegen.OutputDir. Each file from resp.Files is written with os.WriteFile; any OS-level failure aborts with this error.

Source

Thrown at cli/internal/metadataobject/actions/actions.go:294

		data.CodegenConfig.URI = a.getActionsCodegenURI(data.CodegenConfig.Framework)
	}

	resp, err := a.cliExtensionConfig.GetActionsCodegen(data)
	if err != nil {
		return errors.E(
			op,
			fmt.Errorf("error in getting codegen for action %s: %w", data.ActionName, err),
		)
	}

	for _, file := range resp.Files {
		err = os.WriteFile(
			filepath.Join(a.ActionConfig.Codegen.OutputDir, file.Name),
			[]byte(file.Content),
			0o644,
		)
		if err != nil {
			return errors.E(op, fmt.Errorf("error in writing codegen file: %w", err))
		}
	}

	return nil
}

func (a *ActionConfig) Validate() error {
	return nil
}

func (a *ActionConfig) CreateFiles() error {
	var (
		op     errors.Op = "actions.ActionConfig.CreateFiles"
		common types.Common
	)

	data, err := yaml.Marshal(common)
	if err != nil {

View on GitHub (pinned to 724551b9ae)

Solutions

Check the wrapped OS error, then create the output directory: mkdir -p <codegen.output_dir from actions.yaml>
Ensure the directory is writable by the current user
Verify no directory exists with the same name as a file the codegen writes
Re-run the codegen command

Example fix

# actions.yaml
# before
codegen:
  output_dir: src/generated/
# after (create the dir, or point to an existing one)
mkdir -p src/generated

Defensive patterns

Strategy: validation

Validate before calling

outDir := cfg.ActionConfig.Codegen.OutputDir
if err := os.MkdirAll(outDir, 0o755); err != nil {
    return fmt.Errorf("cannot prepare codegen output dir: %w", err)
}

Try / catch

if err := cfg.Codegen(name, pld); err != nil {
    if pe := new(fs.PathError); errors.As(err, &pe) {
        _ = os.MkdirAll(cfg.ActionConfig.Codegen.OutputDir, 0o755)
        // retry codegen once
    }
}

Prevention

Add codegen.output_dir creation to project bootstrap scripts
Point output_dir at an existing, committed directory
Ensure no directory shares a name with generated files

When it happens

Trigger: Running actions codegen when the configured output directory (from actions.yaml codegen.output_dir) does not exist or is not writable; a generated file name collides with an existing directory.

Common situations: Default output dir (./src/generated/) never created; output_dir changed in actions.yaml to a path that doesn't exist; read-only workspace or container; generated file name like `types.ts` matching an existing directory name.

Related errors

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/c8dc89a6cf3615eb. Report an issue: GitHub.