ts-node treats symbolic links in node_modules as separate files

[jakzo]

Expected Behavior

Compiling a project which contains a file and the project also includes an import of a symlink of that file in node_modules completes successfully, even if the file declares a global identifier which would cause a "duplicate identifier" error if they were two separate files.

Common monorepo setups such as Yarn workspaces create symlinks from node_modules to files in the source. Typescript treats a symbolic link from node_modules to a file as the same file it links to in order to prevent these issues. Note that this behaviour is only when the file is in node_modules.

Actual Behavior

ts-node emits a "duplicate identifier" error for this case.

Steps to reproduce the problem

Create a Yarn workspaces project and import a file from another package which declares an identifier globally, such as:

declare module "http" {
  class X {}
}

Minimal reproduction

https://github.com/jakzo/ts-node-symlink-issue

Specifications

• ts-node version: ts-node v8.10.2
• node version: node v12.16.3
• TypeScript version: compiler v3.9.3
• tsconfig.json, if you're using one:

{
  "include": ["./"],
  "exclude": ["node_modules"],
  "compilerOptions": {
    "moduleResolution": "node",
    "outDir": "./dist/",
    "types": ["node"]
  }
}

• Operating system and version: Mac 15.5

[cspotcode]

Sounds like a duplicate of some other bug reports. The underlying issue is that ts-node doesn't give TS a realpath function, so symlinks are never resolved. For an explanation: #970

See also: #876, #797, #956, #819, #990

[cspotcode]

Closing as a duplicate, but if you think that is a mistake, please reply and we can reopen.