Empty `TS_NODE_IGNORE` defaults to `node_modules/`

[inad9300]

Expected Behavior

Running TS_NODE_IGNORE= webpack should make ts-node (internally used by webpack) take into account references to TypeScript files contained in node_modules/.

Actual Behavior

It behaves the same as if TS_NODE_IGNORE was not defined at all. When setting TS_NODE_IGNORE to a dummy value, e.g. TS_NODE_IGNORE=/non-existent-directory webpack, things work as expected.

Steps to reproduce the problem

Clone https://github.com/inad9300/webpack-typescript-loader/tree/ts-node-ignore, run npm i and npm start. Compare this with npm run really-start.

Specifications

• ts-node version: 9.1.1
• node version: 14.16.0
• TypeScript version: 4.2.4
• tsconfig.json, if you're using one:

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node"
  }
}

• Operating system and version: latest macOS

[cspotcode]

Marked as "help wanted" because this is a straightforward fix, a good first issue for an external contributor, and we already have TS_NODE_SKIP_IGNORE which achieves the same effect, so the severity is low.

If anyone wants to implement this feature, please also think about corner cases and documentation updates, if appropriate. TS_NODE_IGNORE is interpreted as a regexp. I think that technically an empty regexp means "match everything", but I'm not sure and I agree that's confusing.

Here are links to some relevant bits of code:

ts-node/src/index.ts

Lines 509 to 516 in 03355c1

	const shouldIgnore = createIgnore(
	ignoreBaseDir,
	options.skipIgnore
	? []
	: (options.ignore || ['(?:^|/)node_modules/']).map(
	(str) => new RegExp(str)
	)
	);

ts-node/src/index.ts

Line 321 in 03355c1

ignore: split(env.TS_NODE_IGNORE),