🏗♻️ Share extension generator implementation (#34002)

Refactors the filesystem-read extension generator built for **Bento**, so that it can be used for **Classic** components.

- Moves templates in `bento/` to `template/bento/extensions/`.
  This follows: `template/${templateName}/${rootDirPath...}`.
  - Code rules can now be excluded from `template/**`
  - We now start from the root directory so we can generate an `examples/` file for Classic.
  - (It also means that we can use the generator for anything and not just extensions.)

- Moves some existing templates to `template/shared` which is used for both Bento and Classic.

- Rewrites Classic templates to match the new filesystem-read generator, into `template/classic`.

- The Classic generator would `prettier`-format, while Bento would not. Generated files are now always formatted.

- Adds a few tests.

New template directory structure:
```
build-system/tasks/make-extension/template
├── bento
│   └── extensions
│       └── amp-__component_name_hyphenated__
│           ├── OWNERS
│           └── __component_version__
│               ├── amp-__component_name_hyphenated__.js
│               ├── base-element.js
│               ├── component.js
│               ├── component.jss.js
│               ├── component.type.js
│               ├── storybook
│               │   ├── Basic.amp.js
│               │   └── Basic.js
│               └── test
│                   └── test-amp-__component_name_hyphenated__.js
├── classic
│   ├── examples
│   │   └── amp-__component_name_hyphenated__.html
│   └── extensions
│       └── amp-__component_name_hyphenated__
│           ├── OWNERS
│           └── __component_version__
│               ├── amp-__component_name_hyphenated__.js
│               └── test
│                   ├── test-amp-__component_name_hyphenated__.js
│                   └── __validator__-amp-__component_name_hyphenated__.html
└── shared
    └── extensions
        └── amp-__component_name_hyphenated__
            ├── __component_version__
            │   └── amp-__component_name_hyphenated__.css
            ├── amp-__component_name_hyphenated__.md
            └── __validator__-amp-__component_name_hyphenated__.protoascii
```

.eslintignore

@@ -31,7 +31,7 @@ validator/export
 build-system/babel-plugins/**/fixtures/**/*.js
 build-system/babel-plugins/**/fixtures/**/*.mjs
 build-system/server/app-index/test/*.js
-build-system/tasks/make-extension/bento/amp-__component_name_hyphenated__/**/*
+build-system/tasks/make-extension/template/**/*
 build-system/tasks/visual-diff/snippets/*.js
 extensions/amp-a4a/0.1/test/testdata/**
 src/purifier/noop.js

.prettierrc

@@ -9,7 +9,7 @@
       "options": {"parser": "json5"}
     },
     {
-      "files": "build-system/tasks/make-extension/bento/amp-__component_name_hyphenated__/**",
+      "files": "build-system/tasks/make-extension/template/**",
       "options": {
         "requirePragma": true
       }

build-system/pr-check/build-targets.js

@@ -132,6 +132,7 @@ const targetMatchers = {
     return (
       file == 'build-system/tasks/ava.js' ||
       file.startsWith('build-system/tasks/get-zindex/') ||
+      file.startsWith('build-system/tasks/make-extension/') ||
       file.startsWith('build-system/tasks/markdown-toc/') ||
       file.startsWith('build-system/tasks/prepend-global/')
     );

build-system/tasks/ava.js

@@ -26,6 +26,7 @@ async function ava() {
   // (see targetMatchers[Targets.AVA])
   const testFiles = [
     'build-system/tasks/get-zindex/get-zindex.test.js',
+    'build-system/tasks/make-extension/test/test.js',
     'build-system/tasks/markdown-toc/test/test.js',
     'build-system/tasks/prepend-global/prepend-global.test.js',
   ];

build-system/tasks/make-extension/OWNERS

@@ -8,9 +8,10 @@
         // Outreach group maintains extension boilerplate/template.
         {name: 'ampproject/wg-outreach'},
 
-        // Most new extensions are reviewed by this group. It's in their
+        // Most new extensions are reviewed by these groups. It's in their
         // interest to maintain the extension generator.
         {name: 'ampproject/wg-components'},
+        {name: 'ampproject/wg-bento'},
       ],
     },
   ],

build-system/tasks/make-extension/format.js

@@ -0,0 +1,29 @@
+/**
+ * Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const {getOutput} = require('../../common/process');
+
+/**
+ * @param {Array<string>} files
+ * @return {Object}
+ */
+function format(files) {
+  return getOutput(`npx prettier --ignore-unknown --write ${files.join(' ')}`);
+}
+
+module.exports = {
+  format,
+};