build: ESLint rule to check/add license headers (#11716)

.eslintrc.js

@@ -149,6 +149,8 @@ module.exports = {
     'rulesdir/prettier-comments': 'error',
     // Enforces consistent file extension
     'rulesdir/extensions': 'error',
+    // Enforces license headers on files
+    'rulesdir/check-license': 'warn',
   },
   overrides: [
     {

tools/eslint/src/check-license.ts

@@ -0,0 +1,82 @@
+/**
+ * @license
+ * Copyright 2024 Google Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type {TSESTree} from '@typescript-eslint/utils';
+import {ESLintUtils} from '@typescript-eslint/utils';
+
+const createRule = ESLintUtils.RuleCreator(name => {
+  return `https://github.com/puppeteer/puppeteer/tree/main/tools/eslint/${name}.ts`;
+});
+
+const copyrightPattern = /Copyright ([0-9]{4}) Google Inc\./;
+
+const currentYear = new Date().getFullYear;
+
+const licenseHeader = `/**
+ * @license
+ * Copyright ${currentYear} Google Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */`;
+
+const enforceLicenseRule = createRule<[], 'licenseRule'>({
+  name: 'check-license',
+  meta: {
+    type: 'layout',
+    docs: {
+      description: 'Validate existence of license header',
+      requiresTypeChecking: false,
+    },
+    fixable: 'code',
+    schema: [],
+    messages: {
+      licenseRule: 'Add license header.',
+    },
+  },
+  defaultOptions: [],
+  create(context) {
+    const sourceCode = context.sourceCode;
+    const comments = sourceCode.getAllComments();
+    const header =
+      comments[0]?.type === 'Block' && isHeaderComment(comments[0])
+        ? comments[0]
+        : null;
+
+    function isHeaderComment(comment: TSESTree.Comment) {
+      if (comment && comment.range[0] >= 0 && comment.range[1] <= 88) {
+        return true;
+      } else {
+        return false;
+      }
+    }
+
+    return {
+      Program(node) {
+        if (
+          header &&
+          header.value.includes('@license') &&
+          header.value.includes('SPDX-License-Identifier: Apache-2.0') &&
+          copyrightPattern.test(header.value)
+        ) {
+          return;
+        }
+
+        // Add header license
+        if (!header || !header.value.includes('@license')) {
+          const startLoc: [number, number] = [0, 88];
+          context.report({
+            node: node,
+            messageId: 'licenseRule',
+            fix(fixer) {
+              return fixer.insertTextBeforeRange(startLoc, licenseHeader);
+            },
+          });
+        }
+      },
+    };
+  },
+});
+
+export = enforceLicenseRule;