jestjs/jest · error · Error

The first argument to require.resolve.paths must be a string

Error message

The first argument to require.resolve.paths must be a string. Received null or undefined.

What it means

Thrown by `RequireBuilder.resolvePaths` (cjsRequire.ts:177-181) when `require.resolve.paths` is called with `null` or `undefined`. Mirrors the `require.resolve` guard: the runtime needs a defined string before computing search paths.

Source

Thrown at packages/jest-runtime/src/internals/cjsRequire.ts:178

    try {
      return this.resolution.resolveCjs(from, moduleName);
    } catch (error) {
      const module = this.resolution.getCjsMockModule(from, moduleName);
      if (module) {
        return module;
      }
      throw error;
    }
  }

  private resolvePaths(
    from: string,
    moduleName: string | undefined,
  ): Array<string> | null {
    const fromDir = path.resolve(from, '..');
    if (moduleName == null) {
      throw new Error(
        'The first argument to require.resolve.paths must be a string. Received null or undefined.',
      );
    }
    if (moduleName.length === 0) {
      throw new Error(
        'The first argument to require.resolve.paths must not be the empty string.',
      );
    }

    if (moduleName[0] === '.') {
      return [fromDir];
    }
    if (this.resolution.isCoreModule(moduleName)) {
      return null;
    }
    const modulePaths = this.resolution.getModulePaths(fromDir);
    const globalPaths = this.resolution.getGlobalPaths(moduleName);
    return [...modulePaths, ...globalPaths];

View on GitHub (pinned to f49721c78e)

Solutions

1. Validate the argument is a string first.
2. Provide a default module name.
3. Move the call behind a conditional that guarantees the value is set.

Example fix

// before
const searchPaths = require.resolve.paths(maybeModule); // throws when undefined

// after
const searchPaths =
  typeof maybeModule === 'string'
    ? require.resolve.paths(maybeModule)
    : null;

if (typeof name !== 'string') {
  throw new Error('require.resolve.paths needs a string');
}
require.resolve.paths(name);

function isString(v: unknown): v is string {
  return typeof v === 'string';
}

When it happens

Trigger: `require.resolve.paths(null)` or `require.resolve.paths(someOptional)` where `someOptional` is undefined.

Common situations: Tooling that introspects Node's resolution paths using a variable that came from optional config or an env var.

Related errors

• The first argument to require.resolve must be a string. Rece
• The first argument to require.resolve.paths must not be the
• @jest/diff-sequences: ${name} typeof ${typeof arg} is not a
• @jest/diff-sequences: ${name} value ${arg} is not a safe int
• @jest/diff-sequences: ${name} value ${arg} is a negative int

AI-assisted analysis of jestjs/jest@f49721c78e (2026-08-03). Data as JSON: /data/errors/04a4a50f5d0f7b49.json. Report an issue: GitHub.