Get original file path from within Webpack loader

Question

I'm building a custom Webpack loader. What the loader does is unimportant, but it transforms JSON in some way and uses paths from the JSON in order to resolve certain other details. In my loader.js I need a way of getting the original path of the JSON file being loaded such that I can resolve other paths properly.

Take this simple loader and config:

loader.js

module.exports = function (source) {
  
  /* Do some file lookups based on source and modify source */
  this.callback(null, source)

}

webpack.config.js

module.exports = {
  /* ... */
  module: {
    rules: [
      {
        test: /\.json$/i,
        use: ['loader'],
      },
    ],
  },
};

The loader is working (being used), but any business logic I add needs to be path-aware such that it can do lookups on the file system.

Because this is a JSON loader, the source var in the loader function is passed as raw JSON content, with no details about which file the JSON was loaded from. How does one go about getting path information from within the loader such that I can perform other file lookups based on the content from source?

Ascidian

Answer 1

It turns out the property I was looking for is available via the execution context property this, as resourcePath.

module.exports = function (source) {
  
  console.log('The original file was here:', this.resourcePath)

  this.callback(null, source)

}

Here is the (rather sparse) documentation.

If anybody can think of a better/more future-proof way of getting this path then feel free to comment or post another answer.

Ascidian