Fix dependency resolution when using pnpm

[weichensw]

• Add realpath to moduleResolutionHost so that TypeScript could follow symlink as it supposed to be
• Now that typescript follow symlink, npmLink test fails in 2.8.1 due to Guidance on shipping ts within node_modules microsoft/TypeScript#12358, fixed by modifying tsconfig file. (Also related to Add allowTsInNodeModules option for importing .ts files from node_modules. #773)
• Created a new test to cover this scenario.

Fix #768

[weichensw]

I attempted to create a execution-test but couldn't get pnpm to install nested file-based dependency. See this branch for an example:

• The project depends on file: pkg1
• pkg1 depends on file:../pkg2.

After pnpm i, pkg2 couldn't be found in node_modules, only pkg1 could be found. Is this expected @zkochan?

So in order to create a unit test I would need to include a real npm package that exhibits this re-export behavior, one that I know of is office-ui-fabric-react. But I am worried that installing real packages might slow down your tests too much. @johnnyreilly If you are OK then I could do that.

[zkochan]

@xbtsw the way pnpm currently works, it only symlinks directory dependencies but does not run install in the external package.

Though you can run pnpm recursive link in that project and it will do what you expected from pnpm install

[weichensw]

It turns out to be using a folder dependency cannot trigger the error. The dependencies needs to be downloaded from a remote repository.

[johnnyreilly]

But I am worried that installing real packages might slow down your tests too much. @johnnyreilly If you are OK then I could do that.

I am okay with that! Go forth and conquer!

[weichensw]

@johnnyreilly The test is added. I am ready to merge. Please kindly review and comment 🤝

[johnnyreilly]

Will do! I'm away from a keyboard for the next 5 days or so. Will check when I'm back. Thanks for your work!

[johnnyreilly]

Thanks for your work! Released with https://github.com/TypeStrong/ts-loader/releases/tag/v4.3.0