🐛 BUG: this handling in static blocks results in undefined

[avaer]

Which Cloudflare product(s) does this pertain to?

Wrangler

What versions are you using?

wrangler 3.100.0

What operating system and version are you using?

MacOS Sequoia

Please provide a link to a minimal reproduction

No response

Describe the Bug

The following minimal worker script doesn't seem to behave correctly wrt static blocks:

class lol {
  static {
    console.log('this 1', this);
  }
};

class lol2 {
  static a = 1;
  static {
    console.log('this 2', this);
  }
}

export default {};

In the browser and node, both this are defined, which seems correct.
However, in wrangler, the second this is undefined. Removing the static a = 1; seems to make a difference and results in the correct static block behavior.

Is this a specification implementation bug in the wrangler JS runtime?

Please provide any relevant error logs

⎔ Starting local server...
this 1 [class lol]
this 2 undefined

[avaer]

I ran into this in the @discordjs/ws library.

[jasnell]

Unable to reproduce the issue in workerd directly. Are you making use of wranglers transcoding mechanisms? For instance, are you using typescript or any kind of bundling?

Specifically, syntax like this is handled by v8, the same as node.js, so there should be no difference in behavior in the runtime and quick testing demonstrates that. However, I can imagine something in the transcoding process getting in the way... in which case this issue should be transfered over to the wrangler repo

[avaer]

Yes, I believe it is using the internal wrangler jsx bundling.

wrangler.toml:

name = "blah"
main = "main.jsx"
compatibility_date = "2024-09-23"
compatibility_flags = [ "nodejs_compat" ]
workers_dev = true

rules = [
  { type = "Text", globs = ["**/*.sql", "**/*.sql?raw"], fallthrough = true },
  { type = "Text", globs = ["**/*.txt", "**/*.txt?raw"], fallthrough = true },
  { type = "Text", globs = ["**/*.env", "**/*.env?raw"], fallthrough = true },
  { type = "Text", globs = ["**/*.cdc", "**/*.cdc?raw"], fallthrough = true },
  { type = "Text", globs = ["**/*.csv", "**/*.csv?raw"], fallthrough = true }
]

[[durable_objects.bindings]]
name = "AGENT"
class_name = "DurableObject"

[[migrations]]
tag = "v1"
new_classes = ["DurableObject"]

[vars]
WORKER_ENV = "production"

[jasnell]

@dario-piotrowicz ... any ideas here?

[dario-piotrowicz]

This is 100% a building issue

This can be clearly seen with wrangler dev by running the same worker with and without the --no-bundle flag:

And it is actually an issue with esbuild (which we use for bundling) that I reproduced in node itself without workerd being involved at all:
https://github.com/dario-piotrowicz/esbuild17-static-init-blocks-bundling-bug-repro

The issue has actually already been fixed in esbuild (in 0.18.2) but unfortunately wrangler is stuck at 0.17.19 (see: #5222) so I think that this will be fixed whenever we can bump the esbuild version there (but I have no idea when, @penalosa might have an idea about that).

[dario-piotrowicz]

@penalosa I've transferred the issue back to workers-sdk since as I mentioned in my comment I am pretty sure that this is a wrangler issue, I hope you don't mind, please let me know if you disagree 🙂

[penalosa]

Thanks for diagnosing, @dario-piotrowicz! This will be fixed in the upcoming Wrangler v4, which you can try out by installing wrangler@next

[dario-piotrowicz]

Thanks for diagnosing, @dario-piotrowicz! This will be fixed in the upcoming Wrangler v4, which you can try out by installing wrangler@next

Yay, that sounds great 😄

And yes I can confirm that the issue seem to be fixed in wrangler@next 🙂

[penalosa]

I'm going to close this—it was fixed for v4 in #6884, and will be released as part of Wrangler v4 soon. In the meantime, you can access this fix via wrangler@next