[Bug]: this.sourceMap in the LoaderContext is false when using SourceMapDevToolPlugin

[colinaaa]

System Info

System:
OS: macOS 14.6.1
CPU: (12) arm64 Apple M2 Max
Memory: 30.78 GB / 96.00 GB
Shell: 3.7.1 - /opt/homebrew/bin/fish
npmPackages:
@rspack/cli: ^1.0.5 => 1.0.5
@rspack/core: ^1.0.5 => 1.0.5

Details

I'm using custom configuration of SourceMapDevToolPlugin, both Webpack and Rspack documentation shows that I should set devtool: false.

https://webpack.js.org/plugins/source-map-dev-tool-plugin/#root
https://rspack.dev/plugins/webpack/source-map-dev-tool-plugin

But after I set devtool: false, I found the source-map is not correctly generated.

After dive into the compilation process, I found that is caused by the this.sourceMap changes to false in my custom loader.

// loader.js
export default function(content) {
  const callback = this.async()
  const result = transform(content, { sourceMap: this.sourceMap }) // this.sourceMap === false
  callback(null, result.code, result.map) // result.map === false, result in no source-map generated
}

The Rspack directly use devtool to setup loaderContext.sourceMap:

rspack/packages/rspack/src/loader-runner/index.ts

Lines 556 to 558 in 2ec06e4

	loaderContext.sourceMap = compiler.options.devtool
	? isUseSourceMap(compiler.options.devtool)
	: false;

But Webpack will update the value in the SourceMapDevToolModuleOptionsPlugin:

https://github.com/webpack/webpack/blob/dae16ad11e2d2accddc549a92082da3d2e667b01/lib/SourceMapDevToolModuleOptionsPlugin.js#L31

Reproduce link

https://github.com/colinaaa-reproductions/rspack-loader-context-sourcemap

Reproduce Steps

1. Run pnpm install
2. Run pnpm build:webpack
3. Run node webpack-dist/main.js // show true
4. Run pnpm build:rspack
5. Run node rspack-dist/main.js // show false

[ckken]

class no work:

classDemo.js

export class ClassDemo {
  log() {
    console.log(`ClassDemo.name`)
  }
}
export default new ClassDemo()

App.js

import classDemo from './classDemo'
classDemo.log()

devtool

[ckken]

class no work:

classDemo.js

export class ClassDemo {
log() {
console.log(ClassDemo.name)
}
}
export default new ClassDemo()

App.js

import classDemo from './classDemo'
classDemo.log()

devtool

in build