jestjs/jest · error · Error

Cannot parse as JSON

Error message

Cannot parse ${filePath} as JSON: ${error.message}

What it means

The haste-map worker reads and JSON.parses every `package.json` it encounters during the crawl to extract the package name as a haste ID. If `JSON.parse` throws (malformed JSON, trailing comma, BOM, comments), the worker re-throws a descriptive Error naming the file and the parse error message, with the original error attached as `cause`. This stops processing of that file.

Solutions

1. Open the file named in the error message and run it through a JSON validator or `npx jsonlint <file>`.
2. Fix the specific syntax error the embedded `${error.message}` describes (e.g. 'Unexpected token').
3. If the file is in node_modules, reinstall the offending package: `npm ci`.
4. Add the path to `modulePathIgnorePatterns` or `roots` exclusion if it is an unrelated generated file.

Example fix

// before — broken package.json
{
  "name": "my-pkg",
  "version": "1.0.0",   // trailing comma
}
// after
{
  "name": "my-pkg",
  "version": "1.0.0"
}

// Validate every package.json in the crawl path before building.
import { readFileSync } from 'node:fs';
import glob from 'fast-glob';
function validatePackageJsons(rootDir: string) {
  for (const file of glob.sync(`${rootDir}/**/package.json`, { ignore: '**/node_modules/**' })) {
    try { JSON.parse(readFileSync(file, 'utf8')); }
    catch (e) { throw new Error(`Invalid JSON in ${file}: ${(e as Error).message}`); }
  }
}

function isValidJsonFile(filePath: string): boolean {
  try { JSON.parse(readFileSync(filePath, 'utf8')); return true; }
  catch { return false; }
}

When it happens

Trigger: worker() at worker.ts:49 checks `filePath.endsWith(PACKAGE_JSON)`, calls `JSON.parse(getContent())` at line 52, and the catch at line 59 re-throws the wrapped error at line 60. Any package.json with invalid JSON syntax triggers it.

Common situations: A hand-edited package.json with a trailing comma, single quotes, or a comment; a corrupted/truncated file from a failed git merge; a generated package.json with a NaN or unquoted key; node_modules package.json overwritten by a broken postinstall script.

Related errors

• Could not find a "package.json" file in
• Attempted to display seed but seed value is undefined
• babel-jest: Babel ignores
• Crawler retry failed: Original error
• Custom export conditions specified but they are not an…

AI-assisted analysis of jestjs/jest@8e6d128e4a (2026-08-10). Data as JSON: /api/errors/7b9019af1116773c. Report an issue: GitHub.

Appendix: source

Thrown at packages/jest-haste-map/src/worker.ts:60

    if (content === undefined) {
      content = fs.readFileSync(filePath, 'utf8');
    }

    return content;
  };

  if (filePath.endsWith(PACKAGE_JSON)) {
    // Process a package.json that is returned as a PACKAGE type with its name.
    try {
      const fileData = JSON.parse(getContent());

      if (fileData.name) {
        const relativeFilePath = path.relative(rootDir, filePath);
        id = fileData.name;
        module = [relativeFilePath, H.PACKAGE];
      }
    } catch (error: any) {
      throw new Error(`Cannot parse ${filePath} as JSON: ${error.message}`, {
        cause: error,
      });
    }
  } else if (!blacklist.has(filePath.slice(filePath.lastIndexOf('.')))) {
    // Process a random file that is returned as a MODULE.
    if (hasteImpl) {
      id = hasteImpl.getHasteName(filePath);
    }

    if (computeDependencies) {
      const content = getContent();
      const extractor = data.dependencyExtractor
        ? await requireOrImportModule<DependencyExtractor>(
            data.dependencyExtractor,
            false,
          )
        : defaultDependencyExtractor;
      dependencies = [

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