Duplicate type declarations with npm link

[lemoinem]

TypeScript Version: 3.2.0-dev.20181031

Search Terms: npm link unrelated types peerDependencies

Code: Cannot be easily shown via simple code.

Expected behavior:
While developing a library with peerDependencies (e.g., rxjs), npm-linked modules can be used during development.

Actual behavior:
npm-linked modules are impossible to use, because the peerDependencies installed in the npm-linked modules (since we have npm install --dev) conflict with the actual peerDependencies.

Playground Link: Cannot be easily shown via simple code.

Related Issues: #20945

While developing a package, say an external Angular Module, we need to test it in a test application to check the integration.

However, this is impossible to do easily. Currently, I have to close all my editors, rename my node_modules, build the application, test, close everything, rename node_modules, edit, build the module and start again.

This is a major pain. This workflow was already hugely requested before (See #20945), but that issue has been locked, without resolution other than "Stop using npm link". This is not a solution during development. Many reproductions are available in the other thread.
npm link is the recommended way of developing packages with npm. And it would be great if TypeScript followed this.

I understand this is far from trivial to solve. Although it has something to do with the was dependencies are loaded across symlinks. (It looks like npm and other tools ignore the node_module, but typescript doesn't, because of symlink shenanigans). This node_modules is above the symlink, and isn't part of the directory hierarchy of the application, but it seems to be crossed-back on the way up while ignoring the symlink.
As I understand it, a solution could be to double check whether the current directory was accessed via a symlink before going up the file hierarchy (and if yes, go up the proper way).

At any rate, it would be great to have feedback from the team regarding an easy and well-documented recommended way for typescript package developers to work and test if npm-link is not the way to go.

[weswigham]

Can you publish a github repo with, say, an npm setup task or the like which sets up a toy project in a way which triggers the problems you're seeing? We've actually done a lot to improve our symlink'd module support over the last year, and #20945 wasn't closed as intended by someone saying "don't use symlinks" - it was closed by an actual PR (#21130) that actually fixed the bug that had been reported with changes to the underlying logic we use to unify packages.

[lemoinem]

Ok, Thanks for your answer.
I'm sorry I misunderstood the original thread.
I'll try to create a minimal reproduction and come back with it as soon as possible.

[lemoinem]

Here is a reproduction repo: https://github.com/lemoinem/typescript-28265
To reproduce: clone and run ./setup.sh

Tell me if there is anything else I can do to help.

[lemoinem]

@weswigham @sheetalkamat This issue still has the "Needs More Info" tag. Is there anything else I can provide to help you help me?

[sheetalkamat]

@lemoinem Your repro uses version 2.7 and 2.9. And just upgrading to typescript@next doesn't seem to work with your build commands. Can you please see if this repros with typescript@latest or typescript@next and provide repro steps accordingly. Thanks

c:\temp\typescript-28265\test-module>node node_modules\typescript\lib\tsc.js -v
Version 2.9.2

c:\temp\typescript-28265\app>node node_modules\typescript\lib\tsc.js -v
Version 2.7.2

[lemoinem]

@sheetalkamat I removed the dependency to angular (which was useless and blocking typescript >2.9 and preventing update beyond typescript >3.2).
I've double checked it still produces the error though.

[sheetalkamat]

@lemoinem In your app the package.json of test-module the version of rxjs is 6.2.0 and in app its 6.3.3 which is causing conflict and hence two of them cannot refer to same sourceFile resulting in the error.

c:\temp\typescript-28265\test-module\node_modules\rxjs>type package.json
{
  "_args": [
    [
      "rxjs@6.2.0",
...
c:\temp\typescript-28265\app>type node_modules\rxjs\package.json
{
  "_args": [
    [
      "rxjs@6.3.3",

Because in your app compiler option preserveSymlinks is not set, when we pick file from the test module it path is mapped to the real path of the test-module and hence the import of 'rxjs' in that takes place in that context causing the conflicting declarations (because of rxjs package version mismatch). Setting preserveSymlinks to true will remove the issue but most likely that's not what you want but want to update the dependency in test-module instead?

[lemoinem]

Updating the test-module package did solve my issue.
I'll close the issue.
Thanks!

[aleclarson]

I'm hitting something similar. My package (A) depends on @types/react@^16.9.4 and another package (B) which depends on @types/react@^16.8.23. The installed versions of @types/react are as follows:

• 16.9.4 in A/node_modules
• 16.9.9 in B/node_modules

When A/node_modules/B is a symlink to B, running tsc -p . in A results in a bunch of type conflict errors. This could be avoided if TypeScript's CLI compared semver ranges to determine if the higher version is compatible with both A and B.