tsconfig-paths rewrite to be broken when import with file extension (.js)

[msimon]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

With a project organised that way:

src:
  - main.ts
  - app.module.ts
  ....
tsconfig.json
...

Defining an import in main.ts the following way:

import { AppModule } from 'src/app.module.js';

result in it being compiled to:

const app_module_1 = require("src/app.module.js");

ignoring the non-relative path to relative path rewrite that should be done by tsconfig-paths.

Removing the .js from the import, result in the correct compilation:

import { AppModule } from 'src/app.module';

const app_module_1 = require("./app.module");

I took a quick look into nest-cli/lib/compiler/hooks/tsconfig-paths.hook.ts to see if I could spot the issues.
My guess is that the match on l.56 does not return anything if the extension is set.

I'll try to ding more into it soon, but I figure I would ask in case there is an obvious fix for this.

Minimum reproduction code

https://github.com/HomeskilletHealthInc/nestJs_import_rewrite_bug

Steps to reproduce

Run:

nest build
cat ./dist/main.js

This code:

import { AppModule } from 'src/app.module';
import { AppService } from 'src/app.service.js';

is compiled to:

const app_module_1 = require("./app.module");
const app_service_js_1 = require("src/app.service.js");

Failing to rewrite src when .js is precise.

Expected behavior

Defining an import in main.ts the following way:

import { AppModule } from 'src/app.module.js';

Should compile to:

const app_module_1 = require("./app.module.js");

Package version

8.1.5

NestJS version

8.2.3

Node.js version

v14.17.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

The reason I would to get the .js is because it is required for ESM

[jmcdo29]

Can you please provide a minimum reproduction repository?

[kamilmysliwiec]

BTW using absolute paths (using "src" in your import paths) is considered as a bad practice

[msimon]

@jmcdo29 https://github.com/HomeskilletHealthInc/nestJs_import_rewrite_bug

@kamilmysliwiec Using absolute path is, but I don't believe that applies to non-relative path. The code will always compile to the same relative path, independently of the service/computer is being compiled on.
The gain of using non-relative import is so much higher imo. It's even supported out of the box by NestJs.

Let me know if I misses something, but I haven't seen any large projects using fully relative path, nor a good argument to use them.

[kamilmysliwiec]

Yeah just to clarify: it applies only to paths that contain src directory (so using rootDir + absolute paths)

[Val-istar-Guo]

I had the same problem and couldn't import an esm package. Do I have to change all absolute paths to relative paths.
Is there any solution to solve this problem temporarily.

[amit78523]

I had the same problem and couldn't import an esm package. Do I have to change all absolute paths to relative paths. Is there any solution to solve this problem temporarily.

I am using this command temporarily nest build && tsc-alias tsc-alias is a node module.

[Ttou]

same problem, microsoft/TypeScript#56350

[demaisj]

Encountered this bug today, here's a minimum reproduction repo and steps:
https://github.com/demaisj/nestjs-tsconfig-path-issuerepro

1. npm install
2. setup path alias in tsconfig.json (done in repo)

"paths": {
  "@/*": ["./src/*"]
}

3. use alias import with .js extension (done in repo)

import { AppService } from "@/app.service.js";

5. npm run start
6. observe the import error from nodejs runtime

node:internal/modules/cjs/loader:1148
  throw err;
  ^

Error: Cannot find module '@/app.service.js'

We can see in the compiled app.module.js file that the import alias without js extension is correctly resolved @/app.controller → ./app.controller contrary to the import alias with explicit extension@/app.service.js → @/app.service.js
Resolving alias with explicit extension would also allow users to work in an ESM environment.

[JeromeYangtao]

I had the same problem and couldn't import an esm package. Do I have to change all absolute paths to relative paths. Is there any solution to solve this problem temporarily.

I am using this command temporarily nest build && tsc-alias tsc-alias is a node module.

Do you have any solution for nest start @amit78523

[kareldonk]

Is there a way to run tsc-alias as a post build step when doing nest start?