How do I get jest to ignore the fairly common `debug` node package?

Question

I've got a node js module that looks like this

"use strict";

var debug = require('debug')('foo');

var Foo = function() {
  this.x = 123;
  debug("init");
};

module.exports = Foo;

And my test looks like this

jest.dontMock('../lib/foo');
jest.dontMock('debug');

describe('footest', function() {
 it('checks the foo', function() {
   var Foo = require('../lib/foo');
   var foo = new Foo();
   expect(foo.x).toBe(123);
 });
});

But when I run jest with

node node_modules/jest-cli/bin/jest.js 

I get

Found 1 matching tests...
 FAIL  __tests__/foo-test.js (0.02s)
? footest › it checks the foo
  - TypeError: /Users/gregg/src/jest-test/lib/foo.js: /Users/gregg/src/jest-test/node_modules/debug/node.js: Cannot read property 'buffer' of undefined
      at Socket.self [as bytesWritten] (net.js:688:8)
      at _getMetadata (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/moduleMocker.js:279:49)
      at _getMetadata (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/moduleMocker.js:286:23)
      at _getMetadata (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/moduleMocker.js:279:27)
      at _getMetadata (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/moduleMocker.js:279:27)
      at Object.module.exports.getMetadata (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/moduleMocker.js:388:20)
      at Loader._generateMock (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:280:56)
      at Loader.requireMock (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:782:43)
      at Loader.requireModuleOrMock (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:897:17)
      at /Users/gregg/src/jest-test/node_modules/debug/node.js:6:11
      at Object.runContentWithLocalBindings (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/utils.js:309:17)
      at Loader._execModule (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:243:9)
      at Loader.requireModule (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:879:10)
      at Loader.requireModuleOrMock (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:899:17)
      at /Users/gregg/src/jest-test/lib/foo.js:3:13
      at Object.runContentWithLocalBindings (/Users/gregg/src/jest-test/node_modules/jest-cli/src/lib/utils.js:309:17)
      at Loader._execModule (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:243:9)
      at Loader.requireModule (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:879:10)
      at Loader.requireModuleOrMock (/Users/gregg/src/jest-test/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:899:17)
      at Spec.<anonymous> (/Users/gregg/src/jest-test/__tests__/foo-test.js:7:14)
      at Timer.listOnTimeout [as ontimeout] (timers.js:110:15)

How do I get jest to ignore the debug package and why does it appear to be making a mock when I told it not to?

Answer 1

Right now there is a bug in jest 0.1.18 (being fixed here, documented here) where core node modules cannot be ignored from being mocked.

Once the pull request is accepted by facebook, this problem should go away.

Until then, you can point your package.json to the repo of the fix:

"jest-cli": "git://github.com/adaschevici/jest.git#cf4c6ff97d7009ff8627dd7d3a59cfeff1f3c8b8"

which should resolve that issue.