[Bug]: Transpiled TS conflicts with js_binary

[paullewis]

What happened?

Moving from rules_ts-1.0.0-rc4 to a newer release fails if there's transpiled TS used as the entry_point for a js_binary:

load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
load("@aspect_rules_swc//swc:defs.bzl", "swc_transpiler")
load("@bazel_skylib//lib:partial.bzl", "partial")
load("@aspect_rules_js//js:defs.bzl", "js_binary")

ts_project(
    name = "src",
    srcs = [
        "src.ts",
    ],
    declaration = True,
    transpiler = partial.make(
        swc_transpiler,
    ),
    tsconfig = "//:tsconfig",
    deps = [
        "//:node_modules/@types/node",
    ],
)

js_binary(
    name = "src-bin",
    entry_point = ":src.js",
)

It looks like there's some kind of conflict with the anticipated output files:

ERROR: file 'src/src.js' is generated by these conflicting actions:
Label: //src:src_transpile, //src:src-bin
RuleClass: swc_transpiler rule, js_binary rule
Configuration: 8c7c8a83495a6b29f5e61b94373e857884c6b6f4ed04fcd868a9a81a5d062e34
Mnemonic: SWCTranspile, CopyFile
Action key: de389923a7de025ef490f7e6b9a234d395f1f6ecb01641df70f2ff4f0cba0cc9, 198c8d00c9d14a3e2ca1aa96583f202cabc88d60e6bf360e2eedd6182abb11df
Progress message: Transpiling with swc //src:src_transpile [swc bazel-out/darwin_arm64-fastbuild/bin/src/src.ts], Copying file src/src.js
PrimaryInput: File:[[<execution_root>]bazel-out/darwin_arm64-fastbuild/bin]src/src.ts, File:[/[path]/repro/ts-build-bug-repro[source]]src/src.js
PrimaryOutput: File:[[<execution_root>]bazel-out/darwin_arm64-fastbuild/bin]src/src.js
ERROR: com.google.devtools.build.lib.skyframe.ArtifactConflictFinder$ConflictException: com.google.devtools.build.lib.actions.MutableActionGraph$ActionConflictException: for src/src.js, previous action: action 'Copying file src/src.js', attempted action: action 'Transpiling with swc //src:src_transpile [swc bazel-out/darwin_arm64-fastbuild/bin/src/src.ts]'

Version

Development (host) and target OS/architectures:

Output of bazel --version: Bazel 5.3.2

Version of the Aspect rules, or other relevant rules from your WORKSPACE or MODULE.bazel file: rules_ts-1.0.X

Language(s) and/or frameworks involved: SWC, JS, TS.

How to reproduce

I made a repro over at https://github.com/paullewis/ts-build-bug-repro.

Any other information?

No response

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[paullewis]

Hmm, it doesn't happen unless SWC is set as the transpiler, interestingly enough 🤔

[thesayyn]

There's been a breaking change in the way the transpiler attribute worked. @jbedard might have the answer

[alexeagle]

I think you just need to use the swc macro rather than the underlying swc_transpiler function.

[gregmagolan]

@alexeagle is right. You need to use the swc macro now in rules_ts so that you get a pre-declared output label for ":src.js". When using swc_transpiler there is no pre-delcared src.js output label so Bazel thinks that :src.js is a source file. Sadly, instead of saying the source file doesn't exist, which would be a nice error message, bazel fails because js_binary creates a copy_to_bin action on the non-existant src.js to get it into the output tree and the output of that actions conflicts with the output of ts_project creating src.js in the output tree.

If you change your load statement to

load("@aspect_rules_swc//swc:defs.bzl", "swc")

and use that as the transpiler then it should work

[paullewis]

Oh I seeeeee - thank you! I'll close this one then 👍🏻

[alexeagle]

Reopening just to see if there's something we can do to improve the error messaging, or maybe avoid that accidental copy_to_bin that makes the symptom (a collision) so unrelated to the cause (a thing that wasn't declared).