TSC fails to emit required files when run below node_modules

TypeScript Version: 3.2.0-dev.20181107

Search Terms: node_modules

Code

/tmp/node_modules/tsc-test/tsconfig.json

{
  "compilerOptions": {
    "outDir": "dist"
  },
  "files": [
    "src/index.ts"
  ]
}

/tmp/node_modules/tsc-test/src/index.ts

import { A } from './A';

export const main = () => {
  console.log('A=', A);
};

/tmp/node_modules/tsc-test/src/A.ts

export const A = 'A';

Expected behavior:

Output files:

• /tmp/node_modules/tsc-test/dist/index.js
• /tmp/node_modules/tsc-test/dist/A.js

Actual behavior:

Output files:

/tmp/node_modules/tsc-test/dist/index.js

"use strict";
exports.__esModule = true;
var A_1 = require("./A");
exports.main = function () {
    console.log('A=', A_1.A);
};

No A.js is output

Notes:

I wanted to build a typescript project as part of an npm postinstall script, to enable installation from npm or from git. In the case of installation from npmjs, dist/ will already exist. In the case of installation from git, dist/ will be missing and build will be run.

After setting this up, I noticed that only files listed in my tsconfig files list were being emitted when installing from git. I looked around for tsconfig or tsc options that may change this behavior, but realized it probably had to do with 'node_modules' being in the path.

I debugged the issue by modifying the built tsc.js. In my case, the problematic code is in nodeModuleNameResolverWorker/tryResolve, specifically here:

const { path: candidate, parts } = normalizePathAndParts(combinePaths(containingDirectory, moduleName));
const resolved = nodeLoadModuleByRelativeName(extensions, candidate, /*onlyRecordFailures*/ false, state, /*considerPackageJson*/ true);
// Treat explicit "node_modules" import as an external library import.
return resolved && toSearchResult({ resolved, isExternalLibraryImport: contains(parts, "node_modules") });

The call to contains(parts, "node_modules") should likely consider the project root directory, and ignore "node_modules" in the path parts above the root.

Start in src/compiler/moduleNameResolver.ts at nodeModuleNameResolverWorker/tryResolve, especially the contains(parts, "node_modules") logic described in the issue. Reproduce the provided /tmp/node_modules/tsc-test project with TypeScript 3.2.0-dev.20181107 and compare emitted files. Done means the build emits both dist/index.js and dist/A.js when the project is below node_modules.