webpack-license-plugin/src/WebpackLicensePlugin.ts

Extracts OSS license information of the npm packages in your webpack output

import type { Chunk, Compilation, Compiler } from 'webpack'
import type IPluginOptions from './types/IPluginOptions'
import type IWebpackPlugin from './types/IWebpackPlugin'
import webpack from 'webpack'
import LicenseFileWriter from './LicenseFileWriter'
import LicenseMetaAggregator from './LicenseMetaAggregator'
import ModuleDirectoryLocator from './ModuleDirectoryLocator'
import OptionsProvider from './OptionsProvider'
import PackageJsonReader from './PackageJsonReader'
import WebpackAlertAggregator from './WebpackAlertAggregator'
import WebpackAssetManager from './WebpackAssetManager'
import WebpackChunkIterator from './WebpackChunkIterator'
import WebpackFileSystem from './WebpackFileSystem'

const WebpackError = webpack.WebpackError
const pluginName = 'WebpackLicensePlugin'

interface ObservedCompiler {
  name: string
  isChild: boolean
}

export default class WebpackLicensePlugin implements IWebpackPlugin {
  private readonly filenames = new Set<string>()
  private createdFiles = false
  private observedCompilers: ObservedCompiler[] = []

  constructor(private pluginOptions: Partial<IPluginOptions> = {}) {}

  public apply(compiler: Compiler) {
    if (typeof compiler.hooks !== 'undefined') {
      compiler.hooks.compilation.tap(
        'webpack-license-plugin',
        this.handleCompilation.bind(this, compiler),
      )
      compiler.hooks.watchRun.tapAsync(
        'webpack-license-plugin',
        this.handleWatchRun.bind(this),
      )
    }
    // @ts-expect-error plugin doesn't exist on compiler
    else if (typeof compiler.plugin !== 'undefined') {
      // @ts-expect-error plugin doesn't exist on compiler
      compiler.plugin(
        'compilation',
        this.handleCompilation.bind(this, compiler),
      )
      // @ts-expect-error plugin doesn't exist on compiler
      compiler.plugin('watchRun', this.handleWatchRun.bind(this))
    }
  }

  public async handleWatchRun(_: unknown, callback: () => void) {
    this.createdFiles = false
    this.observedCompilers = []
    callback()
  }

  public handleCompilation(compiler: Compiler, compilation: Compilation) {
    if (typeof compilation.hooks !== 'undefined') {
      if (typeof compilation.hooks.processAssets !== 'undefined') {
        const boundHandleChunkAssetOptimization
          = this.handleChunkAssetOptimization.bind(
            this,
            compiler,
            compilation,
            compilation.chunks,
          )

        compilation.hooks.processAssets.tapAsync(
          {
            name: 'webpack-license-plugin',
            stage: webpack.Compilation.PROCESS_ASSETS_STAGE_ANALYSE,
          },
          (assets, callback) => boundHandleChunkAssetOptimization(callback),
        )
      }
      else {
        compilation.hooks.optimizeChunkAssets.tapAsync(
          'webpack-license-plugin',
          this.handleChunkAssetOptimization.bind(this, compiler, compilation),
        )
      }
    }
    // @ts-expect-error plugin doesn't exist on compilation
    else if (typeof compilation.plugin !== 'undefined') {
      // @ts-expect-error plugin doesn't exist on compilation
      compilation.plugin(
        'optimize-chunk-assets',
        this.handleChunkAssetOptimization.bind(this, compiler, compilation),
      )
    }
  }

  public async handleChunkAssetOptimization(
    compiler: Compiler,
    compilation: Compilation,
    chunks: Set<Chunk>,
    callback: () => void,
  ) {
    this.observedCompilers.push({
      name: compilation.compiler.name,
      isChild: compilation.compiler.isChild(),
    })

    if (this.createdFiles) {
      const observedCompilersMessage = this.observedCompilers
        .map(({ name, isChild }) => `compiler: ${name}, isChild: ${isChild}`)
        .join('\n')
      const errorMessage = new WebpackError(
        `${pluginName}: Found licenses after license files were already created.\nIf you see this message, you ran into an edge case we thought would not happen. Please open an isssue at https://github.com/codepunkt/webpack-license-plugin/issues with details of your webpack configuration so we can invastigate it further.\n${observedCompilersMessage}`,
      )
      compilation.errors.push(errorMessage)
      callback()
      return
    }

    if (!compilation.compiler.isChild()) {
      this.createdFiles = true
    }

    const alertAggregator = new WebpackAlertAggregator(compilation)
    const optionsProvider = new OptionsProvider(alertAggregator)

    const options = optionsProvider.getOptions(this.pluginOptions)
    alertAggregator.flushAlerts(pluginName)

    const chunkIterator = new WebpackChunkIterator()
    for (const filename of chunkIterator.iterateChunks(compilation, chunks)) {
      this.filenames.add(filename)
    }

    if (compilation.compiler.isChild()) {
      callback()
      return
    }

    const fileSystem = new WebpackFileSystem(compiler.inputFileSystem)
    const packageJsonReader = new PackageJsonReader(fileSystem)
    const licenseFileWriter = new LicenseFileWriter(
      new WebpackAssetManager(compilation),
      new ModuleDirectoryLocator(
        fileSystem,
        compiler.options.context,
        packageJsonReader,
      ),
      new LicenseMetaAggregator(
        fileSystem,
        alertAggregator,
        options,
        packageJsonReader,
      ),
    )

    await licenseFileWriter.writeLicenseFiles([...this.filenames], options)
    alertAggregator.flushAlerts(pluginName)

    callback()
  }
}