fix: source dts files outputted to outDir

[jbedard]

#746 changed this logic to align with outputted .js files which I think makes sense. However js also has the allowJs logic while dts files do not.

---

Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: yes
• Breaking change (forces users to change their own code or config): no
• Suggested release notes appear below: yes/no

Test plan

• Covered by existing test cases
• New test cases added

[aspect-workflows]

Test

All tests were cache hits

176 tests (100.0%) were fully cached saving 12s.

---

Buildifier      Format

[jbedard]

If tsc doesn't support this... should rules_ts? Overall I feel like this workflow makes sense so it's odd tsc seems to not support it. Does the use of ts within bazel make this issue more common which would justify adding this feature despite tsc not supporting it? (imo the answer is yes)

As I understand it the scenario would be:

src/
   a.ts
   types.d.ts

Then ts_project(root_dir="src", out_dir="dist").

If the types within types.d.ts are public then the ts_project output really does need them (because a.d.ts probably imports types.d.ts).

[alexeagle]

Generally the principle here is that we behave the same as tsc as much as possible.
If someone needs to do this, can't they do it in userspace?

[jbedard]

I think users would have to use copy_to_bin or ts_project(assets) to copy the file to the bindir while moving it from rootDir to outDir. But then it won't be in JsInfo.types so it probably won't work when depended on.

That just seems odd. I think this only works outside bazel because the file will still be referenced in src all the time?

[alexeagle]

That's a lot of "probably" and asking questions, are you asking me to answer those questions?

[jbedard]

I'm looking for feedback and opinions because I'm uncertain about this change. I don't like adding functionality, but I don't think such a standard use case should require an ugly workaround in userspace.

This also partially (but incorrectly) worked in the past before #746, and it still (correctly) works if out_dir == root_dir.

[jbedard]

So tsc explicitly doesn't not copy .d.ts files, unlike .js when allowJs. This was intentional from the beginning: microsoft/TypeScript#5112 (comment)

Outside bazel this normally isn't an issue because a) no sandboxing (so you can access the .d.ts even if it isn't outputted to outDir) and b) pnpm symlinks directly into the source for references between projects so these .d.ts are available there as well.

In bazel the non-copied .d.ts are not accessible at all: they are not in the sandbox, they are not in npm packages. Yet they would be copied if in js_library(srcs) which makes this even more odd...?