Support dynamic lazy imports

[petebacondarwin]

Cloudflare workers support imports natively, including runtime import() expressions.

So potentially we could lazy load files by uploading such modules as "external" alongside the entry-point file.

Currently, our build process will bundle all static imports (and statically analysable dynamic imports) into the main entry-point bundle: import()-ed modules are wrapped in a function, actually executing the import() executes the inlined code.

One thing this approach doesn't currently support is imports where the module specifier is not known at build time. For example:

a.js

export const foo = 'A';

b.js

export const foo = 'B';

index.js

async function main() {
  const p = Math.random() > 0.5 ? 'a' : 'b';
  const foo = (await import(`./${p}.js`)).foo;
}
main();

This issues tracks the support for being able to do this via Wrangler 2.

[petebacondarwin]

Closing as a duplicate of #637, which is a superset of this really.

[threepointone]

Actually, it's different. That's about lazy imports (await import(<string literal>)), while this is about dynamic imports (await import(variable))

[bhvngt]

Would love to have this feature. Currently, I am stuck here. I have few variable based dynamic imports that needs to run inside worker.

Is there any workaround or would I have to hard code all the statically analysable dynamic imports upfront for the time being?

[petebacondarwin]

One solution, we could implement, is to add a configuration option to specify additional entry-points for a Worker. These would be bundled using the same tooling as the main entry-point but uploaded as additional modules alongside the main one.
Before we bother to do this, we need to check whether the runtime is now able to support loading these dynamically - I think it does in some form.

[penalosa]

Closing for now, since --no-bundle supports this use case. If there isn't an issue already open for tracking the new module work that's in-progress, we should make one.

[irvinebroque]

Should the docs for --no-bundle be updated to reflect that using --no-bundle supports dynamic imports?

https://developers.cloudflare.com/workers/wrangler/commands/

[penalosa]

@irvinebroque Yes, they probably should