[bazel] Set CLOSURE_COMPILER to workaround RBE+symlinks issue

[kjlubick]

When trying to compile using emscripten/emsdk on Bazel's remote executors, I ran into an error like:

Linking ... failed: (Exit 1): emcc_link.sh failed: error executing command external/emsdk/emscripten_toolchain/emcc_link.sh @bazel-out/wasm-opt-ST-d9bb9c985c3e/bin/...-2.params
node:internal/modules/cjs/loader:936
  throw err;
  ^

Error: Cannot find module './lib/utils'
Require stack:
- /b/f/w/external/emscripten_bin_linux/emscripten/node_modules/.bin/google-closure-compiler
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:94:18)
    at Object.<anonymous> (/b/f/w/external/emscripten_bin_linux/emscripten/node_modules/.bin/google-closure-compiler:20:57)
    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) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [
    '/b/f/w/external/emscripten_bin_linux/emscripten/node_modules/.bin/google-closure-compiler'
  ]
}
node:internal/modules/cjs/loader:936
  throw err;
  ^

By looking at the remote execution logs (e.g. appending --execution_log_json_file=/tmp/execlog.json to my Bazel command), I was able to figure out that Bazel was not preserving symlinks that were created by npm install, but rather uploading the linked file in place of the symlink.

Instead of uploading

.../node_modules/.bin/google-closure-compiler # symlink to ../google-closure-compiler/cli.js
.../node_modules/google-closure-compiler/cli.js
.../node_modules/google-closure-compiler/lib/utils.js

it was uploading

.../node_modules/.bin/google-closure-compiler # copy of ../google-closure-compiler/cli.js
.../node_modules/google-closure-compiler/cli.js
.../node_modules/google-closure-compiler/lib/utils.js

Then, when executing node_modules/.bin/google-closure-compiler, it would try to load node_modules/.bin/lib/utils.js and not be able to find it.

To work around this issue, we can bypass the symlink and run the google-closure-compiler/cli.js ourselves, which is successfully able to load the lib/utils.js and all other dependent files.

#883 is possibly a related issue

[sbc100]

Seems like a reasonable fix to me. Do we need to prefix this command with the node executable, or does the #! work well enough?

[kjlubick]

I tested this locally on my Linux box and in a Linux RBE instance and it seems to work as is.

[sbc100]

I tested this locally on my Linux box and in a Linux RBE instance and it seems to work as is.

If it works, I think it would be safer to do CLOSURE_COMPILER = [NODE_JS, ...] since then we will be sure we are using the configured version of node.

[kjlubick]

I tested this locally on my Linux box and in a Linux RBE instance and it seems to work as is.

If it works, I think it would be safer to do CLOSURE_COMPILER = [NODE_JS, ...] since then we will be sure we are using the configured version of node.

I tried that out and it appears to have worked.