Can't make paths work properly

[BUONJG]

Hello,

I'm trying to use paths property in my tsconfig.json file.

It makes the build work perfectly but execution of generated js is failing.

My tsconfig.json:

{
    "compileOnSave": false,
    "compilerOptions": {
        "outDir": "./dist",
        "baseUrl": "./src",
        "paths": {
            "core/*": [
                "core/*"
            ]
        },
        "sourceMap": true,
        "declaration": false,
        "moduleResolution": "node",
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "target": "es5",
        "typeRoots": [
            "node_modules/@types"
        ]
    },
    "include": [
        "src/**/*"
    ]
}

src/core/service.ts:

export class Service {
    public static log(message: string) {
        console.log('message', message);
    }
}

src/core/index.ts:

export * from './service';

src/index.ts:

import { Service } from 'core';
Service.log('test');

The build is working perfectly

But running dist\index.js I obtain:

Error: Cannot find module 'core'

Am I doing something wrong?

I made a repo to illustrate this:
https://github.com/BUONJG/typescript-paths.git

Many thanks for your support,

Jean-Guy

[RyanCavanaugh]

TypeScript won't rewrite your import filenames - you need to write import declarations that would work at runtime.

[BUONJG]

I don't understand your response, how can I use absolute imports in my example?

I tried to follow documentation:
Path mapping in https://www.typescriptlang.org/docs/handbook/module-resolution.html

Reading this documentation, I thought my example should run but it doesn't.

[mhegazy]

"paths", "baseUrl" and "rootDirs" all inform the compiler of changes to the module locations that you would do in a post-build step or in a module loader, e.g. requireJs.
The compiler treats module names as resource identifiers, and does not mess up with them. if you write "core" in the input the output will have "core", and not "./core" or ./core/index.js". See #18971, #18951, and #16640.
For example above, you can either write import { Service } from './core'; if you are running on node, or import { Service } from './core/index.js'; if you are running in the browser.

[BUONJG]

OK, but how can I make typescript generate javascript code that can be executed with absolute path imports?

I don't want to write import { Service } from './core'; because when I am in a deep folder I have imports like: import {Service } from '../../../../core'

I would prefer to use absolute path as core directory is a root directory of my app.

I understood paths tsconfig property is here to resolve absolute paths and it works, it makes the build work properly.

But the generated javascript is not working.

[mhegazy]

That would be a new feature that we do not support today. feel free to create a new issue for this request.

[BUONJG]

I don't understand, when I read the documentation:
https://www.typescriptlang.org/docs/handbook/module-resolution.html

In the paragraph:

Using "paths" also allows for more sophisticated mappings including multiple fall back locations. Consider a project configuration where only some modules are available in one location, and the rest are in another. A build step would put them all together in one place. The project layout may look like:

projectRoot
├── folder1
│ ├── file1.ts (imports 'folder1/file2' and 'folder2/file3')
│ └── file2.ts
├── generated
│ ├── folder1
│ └── folder2
│ └── file3.ts
└── tsconfig.json
The corresponding tsconfig.json would look like:

{
"compilerOptions": {
"baseUrl": ".",
"paths": {
"": [
"",
"generated/"
]
}
}
}
This tells the compiler for any module import that matches the pattern "" (i.e. all values), to look in two locations.

It seems to correspond to my use case, doesn't?
Do you mean the generated javascript of this example would run with errors too?

[mhegazy]

From the text you quoted, emphasis added:

Using "paths" also allows for more sophisticated mappings including multiple fall back locations. Consider a project configuration where only some modules are available in one location, and the rest are in another. A build step would put them all together in one place. The project layout may look like:
projectRoot
├── folder1
│ ├── file1.ts (imports 'folder1/file2' and 'folder2/file3')
│ └── file2.ts
├── generated
│ ├── folder1
│ └── folder2
│ └── file3.ts
└── tsconfig.json
The corresponding tsconfig.json would look like:
{
"compilerOptions": {
"baseUrl": ".",
"paths": {
"": [
"",
"generated/"
]
}
}
}
This tells the compiler for any module import that matches the pattern "" (i.e. all values), to look in two locations.

[BUONJG]

Thank you mhegazy,

Now I understand why the sample I created is not working properly.

As you suggested I will open a new issue to ask for absolute path imports to avoid imports like ../../../xxx

Regards,