onLoad callback missing properties #27793
Description
What version of Bun is running?
1.3.10+30e609e08
What platform is your computer?
Darwin 25.2.0 arm64 arm
What steps can reproduce the bug?
Bun.plugin({
name: 'plugin',
setup (build) {
build.onLoad({ filter: esmFilter, namespace: 'file' }, args => {
console.log(`kind: ${args.kind}`)
console.log(`namespace: ${args.namespace}`)
console.log(`args: ${args}`)
// Non altering code for demonstration purposes
const content = readFileSync(filename, 'utf8')
return { contents: rewritten, loader: 'js' }
})
},
})
What is the expected behavior?
According to the Bun documentation, the onLoad callback should receive an object containing the following properties:
path: the path to the matching module
importer: the module that imported this module
namespace: the namespace of the module
kind: the kind of import (e.g., entry-point, import-statement, dynamic-import, etc.)
Therefore, args.kind should not be undefined as well as any property other than path.
What do you see instead?
The above code prints:
kind: undefined
namespace: undefined
args: {
path: somePath
}
Additional information
Also, the documentation never states that this plugin is intended for ESM code. Whenever CJS code enters the onLoad phase with loader set to 'js', it returns ESM code, which causes the application to break.