pulumi/pulumi · error

could not write output file %s: %w

Error message

could not write output file %s: %w

What it means

After creating directories, the host writes each generated file with os.WriteFile(0o600); failure returns 'could not write output file <filename>: %w'. This means the directory exists but the file could not be written — typically permissions, the path being a directory, or disk errors.

Source

Thrown at sdk/go/pulumi-language-go/main.go:1543

		return &pulumirpc.GeneratePackageResponse{
			Diagnostics: rpcDiagnostics,
		}, nil
	}
	files, err := codegen.GeneratePackage("pulumi-language-go", pkg, req.LocalDependencies)
	if err != nil {
		return nil, err
	}

	for filename, data := range files {
		outPath := filepath.Join(req.Directory, filename)
		err := os.MkdirAll(filepath.Dir(outPath), 0o700)
		if err != nil {
			return nil, fmt.Errorf("could not create output directory %s: %w", filepath.Dir(filename), err)
		}

		err = os.WriteFile(outPath, data, 0o600)
		if err != nil {
			return nil, fmt.Errorf("could not write output file %s: %w", filename, err)
		}
	}

	return &pulumirpc.GeneratePackageResponse{
		Diagnostics: rpcDiagnostics,
	}, nil
}

func (host *goLanguageHost) Pack(ctx context.Context, req *pulumirpc.PackRequest) (*pulumirpc.PackResponse, error) {
	// Go is very simple, there's nothing it can do to pack so it just copies the source to the target.

	// First read the modfile in the package directory to decide the folder name.
	data, err := os.ReadFile(filepath.Join(req.PackageDirectory, "go.mod"))
	if err != nil {
		return nil, fmt.Errorf("read go.mod: %w", err)
	}
	mod, err := modfile.Parse("go.mod", data, nil)
	if err != nil {

View on GitHub (pinned to 793f7b2e16)

Solutions

1. Check whether the named path is a directory and remove/rename it, then regenerate
2. Ensure write permission on the output directory (chmod/chown) or choose a new -o target
3. Free disk space / check quota
4. Clean the previously generated SDK directory before regenerating

Example fix

// before: stale directory blocks the file
sdk/go/pulumi-provider/internal/
// after
rm -rf sdk/go/pulumi-provider/internal/  # or move it aside, then regenerate

probe := filepath.Join(outDir, ".write-test")
if err := os.WriteFile(probe, []byte("ok"), 0o600); err != nil {
    return fmt.Errorf("cannot write into %s: %w", outDir, err)
}
_ = os.Remove(probe)

if _, err := genPackage(ctx, req); err != nil {
    if strings.Contains(err.Error(), "could not write output file") {
        return cleanOutDirAndRegenerate() // rm stale collisions, check perms/space
    }
    return err
}

When it happens

Trigger: os.WriteFile fails during GeneratePackage: target path exists as a directory, read-only filesystem, immutable file, or quota/disk-full.

Common situations: Previous generation left a directory where a file should go (name collision between generations); output dir owned by another user; editing files in an IDE with a lock; full disk in CI.

Related errors

• read overlay file %q: %w
• create main directory: %w
• could not write output program: %w
• write Pulumi.yaml: %w
• could not create output directory %s: %w

AI-assisted analysis of pulumi/pulumi@793f7b2e16 (2026-08-31). Data as JSON: /api/errors/dd61c086c043030d. Report an issue: GitHub.