Tree-Shaking for `fields` about protobuf-es

[timostamm]

Hey Cyril, I think you're right that the call to newFieldList in generated TS can impact tree-shaking:

protobuf-es/packages/protobuf-test/src/gen/ts/extra/example_pb.ts

Line 63 in 2b2861b

static readonly fields: FieldList = proto3.util.newFieldList(() => [

I believe that adding a /*@__PURE__*/ annotation right before the call expression should help (see #470 for reference).

But before we make this change, we need to verify that it actually works as expected (previous changes were tested with https://github.com/connectrpc/examples-es/tree/main/bundle-size). This will take us a bit to look into, but it looks worthwhile to me.

Thanks for filing the issue!

[smaye81]

Hi @liril-net. We tested adding this annotation to the newFieldList call, but we aren't seeing any effect with Rollup (or most other bundlers). The only bundler that sees an improvement is esbuild. The PR we're using to test is here.

Are you noticing anything different with Rollup? Or do you see anything missing from how we are bundling in our tests?

[timostamm]

Let's close this. See connectrpc/examples-es#1499 (comment) for details.