watchFiles and watchDirs are excluded from Metafile

[alanorozco]

Plugins recently got the ability to return watchFiles or watchDirs that cause a re-build when they are modified.

Our build pipeline (amphtml) is complicated enough that we can't use esbuild's {watch: true}. Instead, we rely on early Metafile results to trigger a re-build ourselves.

We expected watchFiles/Dirs to be included in the Metafile, but they are not.

Build config

import esbuild from 'esbuild';

const myPlugin = {
  name: 'my-plugin',
  setup(build) {
    build.onLoad({filter: /.+/}, (args) => {
      return {
        contents: args.path,
        loader: 'text',
        watchFiles: [args.path],
      };
    });
  },
};

esbuild
  .build({
    entryPoints: ['./source.mjs'],
    bundle: true,
    write: false,
    metafile: true,
    plugins: [myPlugin],
  })
  .then(({metafile}) => {
    console.log(JSON.stringify(metafile, undefined, 2));
  });

source.mjs

import foo from './foo.whatever';

Metafile output vs. expected

  {
    "inputs": {
      "source.mjs": {
        "bytes": 77,
        "imports": []
      },
+     "foo.whatever": {...}
    },
    "outputs": {
      "source.js": {
        "imports": [],
        "exports": [],
        "entryPoint": "source.mjs",
        "inputs": {
          "source.mjs": {
            "bytesInOutput": 132
          }
        },
        "bytes": 191
      }
    }
  }

I understand that the semantics of a watched file and an input file might be different. Regardless of whether they're a part of inputs or not, it would still be super useful if we could obtain returned watchFiles from the build() result.

[evanw]

I just looked into this and I think there are two problems with this proposal:

• Even if you had this information, you still wouldn't be able to watch the correct files since you still wouldn't have esbuild's internal list of paths to watch. I'd like to solve this once with a holistic solution instead of adding this now and then having to change it later.

• People will want access to this data even if there are build errors. Currently the API returns an error instead of a build result when there are build errors, so putting this information in the build result means that it would be inaccessible if there's an error. The build API really needs to be redesigned to fix this.

See also:

• Initial notification to watch.onRebuild #980
• Watch mode behavior on failed first builds #1037
• [Bug?] 'watchFiles' does not appear to be watched after errors #1063
• Getting the dependencies gathered by esbuild #1535

[Kilcekru]

With version 0.17 context was introduced, is this now possible?

The metafile could have new top level properties watchFiles and watchDirs, so they can be differentiated from normal inputs.
If those paths would be normalized like input paths are, then we would have everything to do custom watching.

[aleclarson]

I've added watchFiles and watchDirs to the Metafile in the esbuild-extra package:
https://github.com/aleclarson/esbuild-extra/blob/57218481baebc66efbc2562c5db071b11d3ccc29/src/global.ts#L5-L8
https://github.com/aleclarson/esbuild-extra/blob/57218481baebc66efbc2562c5db071b11d3ccc29/src/index.ts#L78-L90

https://github.com/aleclarson/esbuild-extra