WARNING: Formatting of files failed with the following error

Error message

WARNING: Formatting of files failed with the following error: ${error.message}

What it means

After a schematic runs, the schematics command tries to format the touched files with the configured formatter (Prettier). If formatFiles throws, runSchematic does not fail the command; instead it logs this warning including the formatter error message, since formatting is a post-generation nicety, not a required step.

Source

Thrown at packages/angular/cli/src/command-builder/schematics-command-module.ts:376

      if (!files.size) {
        logger.info('Nothing to be done.');
      }

      if (executionOptions.dryRun) {
        logger.warn(`\nNOTE: The "--dry-run" option means no changes were made.`);

        return 0;
      }

      if (files.size) {
        // Note: we could use a task executor to format the files but this is simpler.
        try {
          await formatFiles(this.context.root, files);
        } catch (error) {
          assertIsError(error);

          logger.warn(
            `WARNING: Formatting of files failed with the following error: ${error.message}`,
          );
        }
      }

      return 0;
    } catch (err) {
      // In case the workflow was not successful, show an appropriate error message.
      if (err instanceof UnsuccessfulWorkflowExecution) {
        // "See above" because we already printed the error.
        logger.fatal('The Schematic workflow failed. See above.');
      } else {
        assertIsError(err);
        logger.fatal(err.message);
      }

      return 1;
    } finally {

View on GitHub (pinned to bb72145f9a)

Solutions

Inspect the error message appended after the warning — it identifies the file/format problem; fix that file or config.
Run the formatter directly on the affected files (`npx prettier --write <file>`) to see the full error and correct it.
Fix .prettierrc issues (invalid options, wrong parser overrides) or add a parser override for custom extensions.
If the generated code itself is malformed, fix the schematic/template producing it; formatting failure is a symptom.

Example fix

// before (.prettierrc)
{ "parser": "babel" }
// after
{ "overrides": [{ "files": "*.ts", "options": { "parser": "typescript" } }] }

Defensive patterns

Strategy: try-catch

Validate before calling

// Validate prettier config parses before generating
import { resolveConfig } from 'prettier';
const cfg = await resolveConfig(process.cwd());
if (cfg === null) console.warn('No prettier config found; formatting may behave unexpectedly');

Try / catch

try {
  await ngGenerate(['component', 'hero']);
} catch (e) {
  // this warning is logged, not thrown; detect it in CLI output
  if (/Formatting of files failed/.test(String(e))) {
    console.warn('Generation succeeded but formatting failed; run `npx prettier --write .` manually.');
  } else throw e;
}

Prevention

Keep a valid .prettierrc with parsers/overrides for every custom file extension schematics may emit.
Run `npx prettier --check .` in CI so formatting regressions surface early.
Treat the warning as non-fatal: files were generated; format them manually with `npx prettier --write .`.
Fix schematics/templates that emit syntactically invalid code, which is the usual root cause.

When it happens

Trigger: Running `ng generate` where the generated/modified files cannot be formatted — e.g. Prettier hits a parse error on generated content, an unsupported/unreadable file, or the formatter misconfigures (bad .prettierrc, missing parser for extension).

Common situations: Custom schematics generating syntactically invalid placeholder code, files with unusual extensions lacking a Prettier parser, permission issues writing files, or a malformed prettier config in the repo.

Related errors

AI-assisted analysis of angular/angular-cli@bb72145f9a (2026-08-30). Data as JSON: /api/errors/b145c066a465734f. Report an issue: GitHub.