tsc doesn't resolve module specified in the typeRoots

[maxkoretskyi]

TypeScript Version: 2.1.5

I have the following directory structure:

tsconfig.json
a.ts
node_modules
|--- custom
     |--- rembo
           |---index.d.ts

The content of index.d.ts is the following:

export declare class Rembo {
    name: string;
}

I reference this module in a.ts:
import {Rembo} from 'rembo';

The package.json is the following:

{
  "compilerOptions": {
    "moduleResolution": "node",
    "module": "es6",
    "target": "es6",
    "typeRoots": [
      "node_modules/custom"
    ]
  }
}

The problem is that rembo module can't be resolved. When compiled, I get the following result:

$ tsc --traceResolution

======== Resolving type reference directive 'rembo', containing file 'D:/Projects/typescript/__inferred type names__.ts', root directory 'D:/Projects/typescript/node_modules/custom'. ========
Resolving with primary search path 'D:/Projects/typescript/node_modules/custom'
File 'D:/Projects/typescript/node_modules/custom/rembo/package.json' does not exist.
File 'D:/Projects/typescript/node_modules/custom/rembo/index.d.ts' exist - use it as a name resolution result.
Resolving real path for 'D:/Projects/typescript/node_modules/custom/rembo/index.d.ts', result 'D:/Projects/typescript/node_modules/custom/rembo/index.d.ts'
======== Type reference directive 'rembo' was successfully resolved to 'D:/Projects/typescript/node_modules/custom/rembo/index.d.ts', primary: true. ========
a.ts(3,21): error TS2307: Cannot find module 'rembo'.

I don't understand why the error, since it reports then:

Type reference directive 'rembo' was successfully resolved to 'D:/Projects/typescript/node_modules/custom/rembo/index.d.ts', primary: true.

[mhegazy]

TypeRoots is useful for global declarations, things that you do not import, e.g. node definition file. when the compiler starts it loads all files under typeRoots and adds them in the global scope.

Seems like this is not what you are looking for, what you need is Path mapping:

{
  "compilerOptions": {
    "moduleResolution": "node",
    "module": "es6",
    "target": "es6",
    "baseUrl": "./",
    "paths": {
      "*" : ["node_modules/custom/*"]
    }
  }
}

This tells the compiler to look under <baseUrl>/node_modules/custom for any import it sees.

[maxkoretskyi]

Thanks a lot for you quick reply. As I understand, the node_modules and node_modules/@types are automatically added to "paths", correct? I have imports of one module residing inside node_modules and the other in node_modules/@types and don't "paths" configured, but both modules are still successfully resolved.

And is my understanding correct that both "typeRoots" and "types" is used for global modules resolve?

[mhegazy]

that is correct. I would not think about typeRoots unless you are using something global, e.g. node. otherwise, just think about modules.

[maxkoretskyi]

Got it, thanks. Where can I read about all supported patterns for paths? For example, can I match part of the module name and provide mappings for that part? Or only * pattern is supported?

[gdamjan]

What if the node_modules including node_modules/@types are outside the source directory alltogether?

SRC=$HOME/Pojects/demo
DEST=/tmp/build

ln -s $SRC/package.json $DEST/package.json
cd $DEST
npm install

cd $SRC
tsc --outDir $DEST/build --typeRoots $DEST/???

this doesn't work

(ts 2.1.6)

[mhegazy]

paths is relative to the baseUrl and not the projectRoot. so you can make the baseUrl whatever you want.