AssetRelocatorPatch.ts

import type { Chunk, Compiler } from 'webpack';

export default class AssetRelocatorPatch {
  private readonly isProd: boolean;

  private readonly nodeIntegration: boolean;

  constructor(isProd: boolean, nodeIntegration: boolean) {
    this.isProd = isProd;
    this.nodeIntegration = nodeIntegration;
  }

  private injectedProductionDirnameCode(): string {
    if (this.nodeIntegration) {
      // In production the assets are found one directory up from
      // __dirname
      return 'require("path").resolve(__dirname, "..")';
    }

    // If nodeIntegration is disabled, we replace __dirname
    // with an empty string so no error is thrown at runtime
    return '""';
  }

  public apply(compiler: Compiler): void {
    compiler.hooks.compilation.tap(
      'asset-relocator-forge-patch',
      (compilation) => {
        // We intercept the Vercel loader code injection and replace __dirname with
        // code that works with Electron Forge
        //
        // Here is where the injection occurs:
        // https://github.com/vercel/webpack-asset-relocator-loader/blob/4710a018fc8fb64ad51efb368759616fb273618f/src/asset-relocator.js#L331-L339
        compilation.mainTemplate.hooks.requireExtensions.intercept({
          register: (tapInfo) => {
            if (tapInfo.name === 'asset-relocator-loader') {
              const originalFn = tapInfo.fn as (
                source: string,
                chunk: Chunk,
              ) => string;

              tapInfo.fn = (source: string, chunk: Chunk) => {
                const originalInjectCode = originalFn(source, chunk);

                // Since this is not a public API of the Vercel loader, it could
                // change on patch versions and break things.
                //
                // If the injected code changes substantially, we throw an error
                if (
                  !originalInjectCode.includes(
                    '__webpack_require__.ab = __dirname + ',
                  )
                ) {
                  throw new Error(
                    'The installed version of @vercel/webpack-asset-relocator-loader does not appear to be compatible with Forge',
                  );
                }

                if (this.isProd) {
                  return originalInjectCode.replace(
                    '__dirname',
                    this.injectedProductionDirnameCode(),
                  );
                }

                return originalInjectCode.replace(
                  '__dirname',
                  // In development, the app is loaded via webpack-dev-server
                  // so __dirname is useless because it points to Electron
                  // internal code. Instead we hard-code the absolute path to
                  // the webpack output.
                  JSON.stringify(compiler.options.output.path),
                );
              };
            }

            return tapInfo;
          },
        });
      },
    );
  }
}