TypeScript compiler option "moduleResolution" is not inferred as it is by `tsc`

[chbrown]

tsc will infer that moduleResolution: "node" if I have module: "commonjs" in my tsconfig.json, even if I also have target: "ES6" (it won't default to node-style moduleResolution if module is set to "es6" and target is also set to "ES6").

However, when compiling with ts-loader via webpack, I have to explicitly add moduleResolution: "node" to my tsconfig file to avoid "Cannot find module 'whatever'" errors in the output.

Adding that line, "moduleResolution": "node" is trivial. Figuring out that I need to add it, to resolve errors that webpack + ts-loader was throwing at me, was frustrating. I would expect ts-loader's (default) behavior to match tsc's (default) behavior, particularly when the ts-loader log message says it's using exactly the same tsconfig file that tsc is using.

[chbrown]

The versions I'm using, FWIW:

├── babel-core@5.8.34
├── babel-loader@5.4.0
├── ...
├── ts-loader@0.7.2
├── typescript@1.8.0-dev.20160105
└── webpack@1.12.9

[jbrantly]

The goal is definitely for ts-loader to work the same as tsc. Do you have a simple file structure/example that you could provide which shows the issue? What does your import look like and where does the module reside?

[chbrown]

Not the simplest example, but here's what I was working on when I encountered this. And the steps to recreate (I just tested this like 5 minutes ago so if you don't hit the same issue then something weird is going on with my machine):

git clone https://github.com/chbrown/unicode-ui.git
cd unicode-ui
npm install                                              # sorry, lots of dependencies
node_modules/.bin/tsc                                    # works
node_modules/.bin/webpack --config webpack.config.js     # works
# edit tsconfig.json, remove this line: "moduleResolution": "node",
node_modules/.bin/tsc                                    # works
node_modules/.bin/webpack --config webpack.config.js     # doesn't work

webpack output with error:

ts-loader: Using typescript@1.8.0-dev.20160108 and /tmp/unicode-ui/tsconfig.json
Hash: d7efaf08b7986c362606
Version: webpack 1.12.10
Time: 5961ms
     Asset     Size  Chunks             Chunk Names
 bundle.js     1 MB       0  [emitted]  app
unidata.js  2.35 MB       1  [emitted]  unidata
   [0] multi unidata 28 bytes {1} [built]
    + 223 hidden modules

ERROR in ./app.tsx
(10,58): error TS2307: Cannot find module 'unidata'.

unidata is another package of mine, installed via npm, pretty simple, but bulky — it just reformats the Unicode 8.0 character data into plain old JavaScript objects, and exposes them via an index.js file using the index.d.ts type definitions that are automatically recognized with TypeScript >= 1.6's handy "node"-style module resolution algorithm.

The import line in question in app.tsx is a run-of-the-mill ES6-style import:

import {Block, getBlocks, Character, getCharacters} from 'unidata';

[jbrantly]

Perfect, thanks!

[jbrantly]

I believe this is related to #111. Basically TypeScript's logic is if module: "commonjs", then moduleResolution: "node" is inferred (see here). However, ts-loader currently does some magic where if target: "ES6" is set then module: "commonjs" is ignored and module: "none" is used instead. This used to be desirable because otherwise TypeScript would throw an error. However, that is no longer the case, so I believe once #111 is fixed this will be as well.

[jbrantly]

This has been fixed and published in v0.8.0.