build(aio): compute which examples to include when watching guide docs (#16213)

PR Close #16213

aio/tools/transforms/authors-package/guide-package.js

@@ -5,22 +5,37 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-const Package = require('dgeni').Package;
-const { basePackage, CONTENTS_PATH, getBoilerPlateExcludes } = require('./base-package');
 
-function createPackage(exampleName) {
+/* eslint no-console: "off" */
+
+const Package = require('dgeni').Package;
+const { basePackage, CONTENTS_PATH } = require('./base-package');
+const { readFileSync } = require('fs');
+const { resolve } = require('canonical-path');
+
+function createPackage(guideName) {
+
+  const guideFilePath = `${CONTENTS_PATH}/guide/${guideName}.md`;
+  const guideFile = readFileSync(guideFilePath, 'utf8');
+  const examples = [];
+  guideFile.replace(/<code-(?:pane|example) [^>]*path="([^"]+)"/g, (_, path) => examples.push('examples/' + path));
+
+  if (examples.length) {
+    console.log('The following example files are referenced in this guide:');
+    console.log(examples.map(example => ' - ' + example).join('\n'));
+  }
+
   return new Package('author-guide', [basePackage])
     .config(function(readFilesProcessor) {
       readFilesProcessor.sourceFiles = [
         {
           basePath: CONTENTS_PATH,
-          include: `${CONTENTS_PATH}/guide/${exampleName}.md`,
+          include: guideFilePath,
           fileReader: 'contentFileReader'
         },
         {
           basePath: CONTENTS_PATH,
-          include: `${CONTENTS_PATH}/examples/*${exampleName}/**/*`,
+          include: examples.map(example => resolve(CONTENTS_PATH, example)),
-          exclude: getBoilerPlateExcludes(),
           fileReader: 'exampleFileReader'
         }
       ];