resolveFromOutDir to Support External Build Orchestrators

#37378 (comment)

• Let's assume "debug" build and "release" build

src/
├── foo
├── bar
└── baz
debug/
├── foo
├── bar
└── baz
release/
├── foo
├── bar
└── baz

• You can build foo, and it knows its own output directory; but when it goes to import from bar, it looks in src/bar instead of debug/bar

  • Instead, we could have a flag that tells TypeScript "resolve relative to the output directory".

• Feels like... maybe should have always been the behavior?

  • There are some subtle issues - possibly around if your input directory is also your output directory.

• Should we enforce that outDir is set and disjoint from the input files?

  • Seems like an overreach, there's a possibly useful configuration here.

• Back to this example

  projects/
  ├── foo/
  │   ├── src
  │   ├── win-out
  │   ├── mac-out
  │   └── linux-out
  ├── bar/
  │   ├── src
  │   ├── win-out
  │   ├── mac-out
  │   └── linux-out
  └── baz/
      ├── src
      ├── win-out
      ├── mac-out
      └── linux-out
  

  • This wouldn't work under any configuration, right? Unless you have some weird hooks in place.

• Weren't we exploring something more ambitious with parameterized project references?

  • Yes, this seems to have more appetite though.

• Any concerns around editor scenarios?

  • Perhaps, if foo relies on bar, if bar isn't built you'll get squiggles.
  • But this is using project references where we'll jump back to the correct source.
    • Is it?

• How do other people use Bazel with TS?

  • Certain companies that use Bazel/Blaze dynamically grow out the file list as needed with a customized tsserver driver.
    • So stuff is possible! But we've never used it and don't have a good feel for it.

• Conclusion: would be willing to take a PR for at least an MVP of the feature so we know we're shipping something that works for Bazel users.