transform does not happen on matched moduleNameMapper file.

🐛 Bug Report

transform isn’t ran on matched modules of moduleNameMapper.

To Reproduce

Read the repository’s readMe.md (npm install && npm test)

Expected behavior

core.ls gets compiled using jest.ls.transformer and there is no error.

Link to repl or repo

https://github.com/ATheCoder/jest-bug

envinfo

  System:
    OS: macOS 10.14.6
    CPU: (8) x64 Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
  Binaries:
    Node: 10.16.1 - /usr/local/bin/node
    Yarn: 1.17.3 - /usr/local/bin/yarn
    npm: 6.9.0 - /usr/local/bin/npm

[SimenB]

The issue is that your core regex matches an internal ./core module in Babel: https://github.com/babel/babel/blob/a2bf68981fbe26a5574607c526818868562fb1f4/packages/babel-types/src/definitions/index.js#L3. This confuses the resolver, which returns your core.ls rather than core.js within Babel. This diff makes your tests pass on my machine:

diff --git i/package.json w/package.json
index f9e730b..7c4c284 100644
--- i/package.json
+++ w/package.json
@@ -16,7 +16,7 @@
     "moduleFileExtensions": ["ls","js", "json", "jsx", "ts", "tsx", "node"],
     "transformIgnorePatterns" : ["<rootDir>/node_modules/"],
     "moduleNameMapper" : {
-      "core": "<rootDir>/dank/core"
+      "^core$": "<rootDir>/dank/core"
     },
     "transform": {
       "^.+\\.ls$": "<rootDir>/jest.ls.transformer"

---

We should probably ignore moduleNameMapper during an internal require…

https://github.com/facebook/jest/blob/8c169d20add61c8831162d8347d2710c07b6b0ef/packages/jest-runtime/src/index.ts#L290-L294 ^ options.isInternalModule is true in this case, but the resolver cares about the user supplied config

@thymikee @jeysal thoughts on that?

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