Runtime plugin onResolve behaves incorrectly for asynchronous imports

[TomasHubelbauer]

What version of Bun is running?

1.1.0+5903a6141

What platform is your computer?

Darwin 23.4.0 arm64 arm

What steps can reproduce the bug?

See the reproduction repository: https://github.com/TomasHubelbauer/bun-runtime-plugin-onResolve-sync-async-import

Make a plugin that uses onResolve to map non-existent paths to existent paths:

import { plugin } from "bun";

await plugin({
  name: "test",
  async setup(build) {
    console.log('Plugin loaded');

    build.onResolve({ filter: /\.demo$/ }, ({ path }) => {
      console.log('onResolve called', path);
      switch (path) {
        case './sync.demo': {
          return { path: './sync.ts' };
        }
        case './async.demo': {
          return { path: './async.ts' };
        }
        default: {
          throw new Error(`Unknown path: ${path}`);
        }
      }
    });
  },
});

Register it in bunfig.toml:

preload = ["./plugin.ts"]

Come up with a script that has sync and async imports matching the plugin's onResolve filter:

import syncDemo from './sync.demo';

console.log('Sync demo', syncDemo);

try {
  const asyncDemo = await import('./async.demo');
  console.log('Async demo', asyncDemo);
}
catch (error) {
  console.error('Error loading async demo', error);
}

Run the script: bun index.ts:

Plugin loaded
onResolve called ./sync.demo
Sync demo Hello, sync!
onResolve called ./async.demo
Error loading async demo error: ENOENT reading "file:./async.ts"

What is the expected behavior?

The async import should resolve to ./async.ts (which it seems to be doing) and then the built-in loader for *.ts should pick it up as it does with the sync import. The output should be this:

Plugin loaded
onResolve called ./sync.demo
Sync demo Hello, sync!
Async demo Module {
  default: "Hello, async!",
}

What do you see instead?

Plugin loaded
onResolve called ./sync.demo
Sync demo Hello, sync!
onResolve called ./async.demo
Error loading async demo error: ENOENT reading "file:./async.ts"

Additional information

This seems to be specifically related to async imports.