Failing run_js_binary example

[jfirebaugh]

I am not sure whether this is a bug or user error. I'm trying to replace a nodejs_binary + genrule combo with js_binary + run_js_binary, but can't get paths to line up.

$ bazel build //example/run_js_binary:run_copy
INFO: Analyzed target //example/run_js_binary:run_copy (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
ERROR: /Users/john/figma/rules_js/example/run_js_binary/BUILD.bazel:9:14: RunBinary example/run_js_binary/out.txt failed: (Exit 1): _copy_launcher.sh failed: error executing command bazel-out/darwin-opt-exec-2B5CBBC6/bin/example/run_js_binary/_copy_launcher.sh example/run_js_binary/in.txt bazel-out/darwin-fastbuild/bin/example/run_js_binary/out.txt

Use --sandbox_debug to see verbose messages from the sandbox
example/run_js_binary/in.txt -> bazel-out/darwin-fastbuild/bin/example/run_js_binary/out.txt
node:internal/fs/utils:344
    throw err;
    ^

Error: ENOENT: no such file or directory, open 'bazel-out/darwin-fastbuild/bin/example/run_js_binary/out.txt'
    at Object.openSync (node:fs:585:3)
    at Object.writeFileSync (node:fs:2153:35)
    at Object.<anonymous> (/private/var/tmp/_bazel_johnfirebaugh/3cc5be9735d30b6128426fd19d172550/execroot/aspect_rules_js/bazel-out/darwin-opt-exec-2B5CBBC6/bin/example/run_js_binary/copy.js:4:4)
    at Module._compile (node:internal/modules/cjs/loader:1101:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:79:12)
    at node:internal/main/run_main_module:17:47 {
  errno: -2,
  syscall: 'open',
  code: 'ENOENT',
  path: 'bazel-out/darwin-fastbuild/bin/example/run_js_binary/out.txt'
}
Target //example/run_js_binary:run_copy failed to build

[alexeagle]

This one is indeed user error, because you're putting paths in the args.

Bazel's implementation of $(location) (and $(execpath) and $(rootpath) which they recommend using instead) will put a bazel-out/[arch]/bin on the front of generated file paths, because they assume the working directory will be the workspace root in the source tree. That assumption is wrong in rules_js.

One workaround is to always put ../../../ in front of such paths, which fixes this PR. You can see that in //examples:bin9 as well.
We've also talked about maybe changing the implementation of these helpers when passed to run_js_binary, or supplying alternative helpers.

[jfirebaugh]

Got it, thanks!

We've also talked about maybe changing the implementation of these helpers when passed to run_js_binary, or supplying alternative helpers.

I would support either of those.