Treeshaking

[smaye81]

No description provided.

[smaye81]

@timostamm here's an example of trying the PURE annotation with newFieldList. It seems to make a difference for esbuild, but no other bundlers. I dug into some of the numbers for the other bundlers and I think this is what's happening:

Parcel

Parcel doesn't seem to be tree-shaking any code from node_modules. If you search for an unused message like SayResponse in the output bundle, you'll see it's included there.

Also, Parcel's numbers aren't affected at all because the output is minified by default and the comments are stripped away. You can turn it off with --no-optimize, but that also turns off tree-shaking 😞

Rollup

The PURE annotation for newFieldList doesn't have any effect. I tried a few different configurations in rollup.config to see if it would help, but to no avail. Rollup's numbers aren't affected at all because the PURE annotation is being stripped in the output bundle.

Rollup claims that it removes invalid annotations and emits a warning, but I don't see any warning in the build (with silent off). The best I can guess is that the TypeScript plugin for Rollup is causing problems and might be stripping this annotation?

Vite

Like Rollup, the PURE annotation for newFieldList doesn't have any effect. Vite's numbers are actually inflated because the PURE annotation is appearing in the output bundle. I also looked into why Vite's output is so much smaller than Rollup's and I believe it's because Vite is doing additional mangling to reduce the size whereas Rollup is just straight bundling.

Webpack

Like Rollup and Vite, the PURE annotation for newFieldList doesn't have any affect. Webpack's numbers aren't affected either because Webpack is minifying the output and stripping the annotation.

[liril-net]

Hi @smaye81 , i think it not works because now the fields call proto3.util.newFieldList to init its value, this makes it always run when the file is imported, for my personal fork, i make it as fields: () => proto3.util.newFieldList() to ensure it as a lazy init and it will works for tree-shaking.

[smaye81]

Ah right. Thanks for the clarification. I don't think we will be making that lazy-initialization refactor since that would be breaking change to generated code. We are actually working on a v2 of Protobuf-ES and plan to release an alpha version shortly, so bundle sizes, etc. will be a bit in flux. We can revisit once we get a better benchmark with the v2 release.

In the meantime, let's keep bufbuild/protobuf-es#769 open just for tracking so that we can verify when the release is ready.

[liril-net]

cool, where can i see the v2 working progress?

[smaye81]

Work is being done on the v2 branch in the https://github.com/bufbuild/protobuf-es repo.

[timostamm]

The @__PURE__ annotation should inform Rollup that the call is free of side-effects, and that it's safe to shake other parts of this module. This might be a shortcoming in Rollup's tree-shaking.