Automatically generate adblock component LICENSE

The generated LICENSE includes a preamble which clarifies that
these licenses apply to lists which are downloaded at run time and
are separate from the Brave Browser (fixes #7150).

lib/build.js

@@ -1,4 +1,5 @@
 const config = require('../lib/config')
+const licensing = require('../lib/licensing')
 const util = require('../lib/util')
 const path = require('path')
 const fs = require('fs-extra')
@@ -93,6 +94,7 @@ const build = (buildConfig = config.defaultBuildConfig, options) => {
   touchOverriddenFiles()
   touchOverriddenVectorIconFiles()
   util.updateBranding()
+  licensing.updateLicenses()
 
   if (config.xcode_gen_target) {
     util.generateXcodeWorkspace()

lib/licensing.js

@@ -0,0 +1,148 @@
+/* Copyright (c) 2019 The Brave Authors. All rights reserved.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+const path = require('path')
+const config = require('./config')
+const fs = require('fs-extra')
+
+const knownMissing = new Set([
+  // Emailed author (henrik@schack.dk) on 2019-11-05.
+  path.join('components', 'third_party', 'adblock', 'lists', 'adblock_dk'),
+  // https://github.com/gfmaster/adblock-korea-contrib/issues/47
+  path.join('components', 'third_party', 'adblock', 'lists', 'adblock-korea-contrib'),
+  // https://github.com/tcptomato/ROad-Block/issues/55
+  path.join('components', 'third_party', 'adblock', 'lists', 'road-block')
+])
+
+const extractLicenseInfo = (directory) => {
+  const readmePath = path.join(directory, 'README.chromium')
+  if (!fs.existsSync(readmePath)) {
+    console.error('Missing README.chromium in ' + directory)
+    process.exit(1)
+  }
+
+  const readmeContents = fs.readFileSync(readmePath).toString().split('\n')
+
+  let metadata = {
+    'slug': path.basename(directory),
+    'Name': null,
+    'URL': null,
+    'License': null,
+    'License File': null,
+    'License Text': null
+  }
+
+  for (const line of readmeContents) {
+    for (let field in metadata) {
+      if (line.indexOf(field + ':') > -1) {
+        metadata[field] = line.substr(field.length + 1).trim()
+        break
+      }
+    }
+  }
+
+  if (!metadata['License File']) {
+    const licensePath = path.join(directory, 'LICENSE')
+    if (fs.existsSync(licensePath)) {
+      metadata['License Text'] = fs.readFileSync(licensePath)
+    } else if (metadata['License'] === 'unknown') {
+      const relativeDir = directory.substr(config.projects['brave-core'].dir.length + 1)
+      if (!knownMissing.has(relativeDir)) {
+        console.log(knownMissing)
+        console.error('Unknown license is not whitelisted: ' + relativeDir)
+        process.exit(1)
+      }
+    } else {
+      console.error('Missing LICENSE in ' + directory)
+      process.exit(1)
+    }
+  }
+
+  return metadata
+}
+
+const readLicenseText = (filename) => {
+  // README.chromium files assume UNIX path separators
+  let fullPath = config.srcDir
+  for (const piece of filename.split('/')) {
+    fullPath = path.join(fullPath, piece)
+  }
+
+  if (!fs.existsSync(fullPath)) {
+    console.error('License file not found: ' + fullPath)
+    process.exit(1)
+  }
+
+  return fs.readFileSync(fullPath)
+}
+
+const generateExternalComponentLicenseFile = (preamble, components) => {
+  let componentNotices = ''
+  let licenseText = ''
+
+  let licenses = {}
+  for (let component of components) {
+    if (componentNotices.length != 0) {
+      componentNotices += '\n'
+    }
+
+    let licenseId = component['License']
+    const licenseText = component['License Text']
+    if (licenseText) {
+      // Custom license
+      licenseId += '-' + component['slug']
+    }
+
+    componentNotices += 'Name: ' + component['Name'] + '\n' +
+                        'URL: ' + component['URL'] + '\n' +
+                        'License: ' + licenseId + '\n'
+
+    if (licenseId === 'unknown') {
+      continue
+    }
+
+    if (!licenses.hasOwnProperty(licenseId)) {
+      if (licenseText) {
+        licenses[licenseId] = licenseText
+      } else {
+        licenses[licenseId] = readLicenseText(component['License File'])
+      }
+    }
+  }
+
+  for (const id of Object.keys(licenses).sort()) {
+    licenseText += '--------------------------------------------------------------------------------\n'
+    licenseText += id + ':\n\n'
+    licenseText += licenses[id] + '\n'
+  }
+
+  return preamble + '\n\n' + componentNotices + '\n' + licenseText
+}
+
+const licensing = {
+  updateLicenses: () => {
+    console.log('regenerating LICENSE files...')
+    const braveComponentsThirdPartyDir = path.join(config.projects['brave-core'].dir, 'components', 'third_party')
+
+    // Brave Ad Block component
+    const braveAdBlockDir = path.join(braveComponentsThirdPartyDir, 'adblock')
+    const braveAdBlockListsDir = path.join(braveAdBlockDir, 'lists')
+
+    let adblockComponents = []
+    fs.readdirSync(braveAdBlockListsDir).forEach(file => {
+      const dirPath = path.join(braveAdBlockListsDir, file)
+      if (fs.statSync(dirPath).isDirectory()) {
+        adblockComponents.push(extractLicenseInfo(dirPath))
+      }
+    })
+
+    let adblockPreamble = 'These licenses do not apply to any of the code shipped with the Brave Browser, but may apply to lists downloaded after installation for use with the Brave Shields feature. The Brave Browser and such lists are separate and independent works.'
+    let adblockLicense = generateExternalComponentLicenseFile(adblockPreamble, adblockComponents)
+    fs.writeFileSync(path.join(braveComponentsThirdPartyDir, 'adblock', 'LICENSE'), adblockLicense)
+    console.log('  - ' + adblockComponents.length + ' sub-components added in adblock/LICENSE')
+  }
+}
+
+module.exports = licensing