How to create a "metafile"?

[taschmidt]

I tried adding metafile: meta.json but got an error from esbuild that metafile must be a boolean. So I changed it to metafile: true. The build ran successfully but I was never able to find any output. Has anyone managed to analyze their esbuild bundle sizes?

[floydspace]

hi @taschmidt, I checked the issue. As long as we are using esbuild's JavaScript API (not CLI), metafile option behaves a bit different, instead of defining a metafile name it receives a boolean value (according to esbuild source code, unfortunately it's not documented), and if the value is true the metadata is returned in the build result as JS object, so you can find your meta in the result variable here:

serverless-esbuild/src/index.ts

Line 229 in b5a9bdb

const result = await build(config);

[taschmidt]

Yeah sorry, I did do some digging in esbuild and saw that it appears you can only do it via code. It might be handy to check here if metafile is true and, if so, dump it out to meta.json or something.

[github-actions]

🎉 This issue has been resolved in version 1.11.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[floydspace]

Hey @taschmidt , if it's still relevant for you, I completed the fix that will save metafile alongside the main bundle.

[taschmidt]

Awesome! Thanks so much!

[linonetwo]

Thanks, get it.

so we can have the solution:

const result = await esbuild.build({
  write: false,
  // we will have result.metafile later
  metafile: true,
  // other configs...
  entryPoints: packageJSON.tsFiles.map((tsFileName) => `./src/${tsFileName}.ts`),
  bundle: true,
  minify: false,
  sourcemap: process.env.CI ? false : 'inline',
  //....
});

// output bundle
for (let out of result.outputFiles) {
  await fs.mkdirp(path.dirname(out.path));
  await fs.writeFile(
    out.path,
    new TextDecoder()
      .decode(out.contents),
    'utf8',
  );
}

if (result.metafile) {
  // use https://bundle-buddy.com/esbuild to analyses
  await fs.writeFile('./dist/metafile.json', JSON.stringify(result.metafile));
}