build: generate proper anchor ids for headings in markdown

package.json

@@ -91,7 +91,7 @@
     "@types/gulp": "3.8.32",
     "@types/inquirer": "^0.0.43",
     "@types/jasmine": "^3.5.4",
-    "@types/marked": "^0.4.2",
+    "@types/marked": "^0.7.4",
     "@types/merge2": "^0.3.30",
     "@types/minimist": "^1.2.0",
     "@types/node": "^12.11.1",
@@ -132,7 +132,7 @@
     "karma-sauce-launcher": "^2.0.2",
     "karma-sourcemap-loader": "^0.3.7",
     "madge": "^3.4.4",
-    "marked": "^0.6.2",
+    "marked": "^1.0.0",
     "merge2": "^1.2.3",
     "minimatch": "^3.0.4",
     "minimist": "^1.2.0",

tools/markdown-to-html/docs-marked-renderer.ts

@@ -1,9 +1,6 @@
-import {Renderer} from 'marked';
+import {Renderer, Slugger} from 'marked';
 import {basename, extname} from 'path';
 
-/** Regular expression that matches whitespace. */
-const whitespaceRegex = /\W+/g;
-
 /** Regular expression that matches example comments. */
 const exampleCommentRegex = /<!--\s*example\(([^)]+)\)\s*-->/g;
 
@@ -13,15 +10,23 @@ const exampleCommentRegex = /<!--\s*example\(([^)]+)\)\s*-->/g;
  */
 export class DocsMarkdownRenderer extends Renderer {
 
+  /** Set of fragment links discovered in the currently rendered file. */
+  private _referencedFragments = new Set<string>();
+
+  /**
+   * Slugger provided by the `marked` package. Can be used to create unique
+   * ids  for headings.
+   */
+  private _slugger = new Slugger();
+
   /**
    * Transforms a markdown heading into the corresponding HTML output. In our case, we
    * want to create a header-link for each H3 and H4 heading. This allows users to jump to
    * specific parts of the docs.
    */
-  heading(label: string, level: number, _raw: string) {
+  heading(label: string, level: number, raw: string) {
     if (level === 3 || level === 4) {
-      const headingId = label.toLowerCase().replace(whitespaceRegex, '-');
-
+      const headingId = this._slugger.slug(raw);
       return `
         <h${level} id="${headingId}" class="docs-header-link">
           <span header-link="${headingId}"></span>
@@ -42,6 +47,11 @@ export class DocsMarkdownRenderer extends Renderer {
       return super.link(`guide/${basename(href, extname(href))}`, title, text);
     }
 
+    // Keep track of all fragments discovered in a file.
+    if (href.startsWith('#')) {
+      this._referencedFragments.add(href.substr(1));
+    }
+
     return super.link(href, title, text);
   }
 
@@ -90,7 +100,26 @@ export class DocsMarkdownRenderer extends Renderer {
    * Method that will be called after a markdown file has been transformed to HTML. This method
    * can be used to finalize the content (e.g. by adding an additional wrapper HTML element)
    */
-  finalizeOutput(output: string): string {
+  finalizeOutput(output: string, fileName: string): string {
+    const failures: string[] = [];
+
+    // Collect any fragment links that do not resolve to existing fragments in the
+    // rendered file. We want to error for broken fragment links.
+    this._referencedFragments.forEach(id => {
+      if (this._slugger.seen[id] === undefined) {
+        failures.push(`Found link to "${id}". This heading does not exist.`);
+      }
+    });
+
+    if (failures.length) {
+      console.error(`Could not process file: ${fileName}. Please fix the following errors:`);
+      failures.forEach(message => console.error(`  -  ${message}`));
+      process.exit(1);
+    }
+
+    this._slugger.seen = {};
+    this._referencedFragments.clear();
+
     return `<div class="docs-markdown">${output}</div>`;
   }
 }

tools/markdown-to-html/transform-markdown.ts

@@ -27,7 +27,8 @@ if (require.main === module) {
   // Bazel bin directory.
   inputFiles.forEach(inputPath => {
     const outputPath = join(bazelBinPath, inputPath.replace(markdownExtension, '.html'));
-    const htmlOutput = markdownRenderer.finalizeOutput(marked(readFileSync(inputPath, 'utf8')));
+    const htmlOutput = markdownRenderer.finalizeOutput(
+        marked(readFileSync(inputPath, 'utf8')), inputPath);
 
     writeFileSync(outputPath, htmlOutput);
   });

yarn.lock

@@ -1324,10 +1324,10 @@
   resolved "https://registry.yarnpkg.com/@types/long/-/long-4.0.0.tgz#719551d2352d301ac8b81db732acb6bdc28dbdef"
   integrity sha512-1w52Nyx4Gq47uuu0EVcsHBxZFJgurQ+rTKS3qMHxR1GY2T8c2AJYd6vZoZ9q1rupaDjU0yT+Jc2XTyXkjeMA+Q==
 
-"@types/marked@^0.4.2":
-  version "0.4.2"
-  resolved "https://registry.yarnpkg.com/@types/marked/-/marked-0.4.2.tgz#64a89e53ea37f61cc0f3ee1732c555c2dbf6452f"
-  integrity sha512-cDB930/7MbzaGF6U3IwSQp6XBru8xWajF5PV2YZZeV8DyiliTuld11afVztGI9+yJZ29il5E+NpGA6ooV/Cjkg==
+"@types/marked@^0.7.4":
+  version "0.7.4"
+  resolved "https://registry.yarnpkg.com/@types/marked/-/marked-0.7.4.tgz#607685669bb1bbde2300bc58ba43486cbbee1f0a"
+  integrity sha512-fdg0NO4qpuHWtZk6dASgsrBggY+8N4dWthl1bAQG9ceKUNKFjqpHaDKCAhRUI6y8vavG7hLSJ4YBwJtZyZEXqw==
 
 "@types/merge2@^0.3.30":
   version "0.3.30"
@@ -7776,16 +7776,16 @@ marked@^0.3.2:
   resolved "https://registry.yarnpkg.com/marked/-/marked-0.3.19.tgz#5d47f709c4c9fc3c216b6d46127280f40b39d790"
   integrity sha512-ea2eGWOqNxPcXv8dyERdSr/6FmzvWwzjMxpfGB/sbMccXoct+xY+YukPD+QTUZwyvK7BZwcr4m21WBOW41pAkg==
 
-marked@^0.6.2:
-  version "0.6.2"
-  resolved "https://registry.yarnpkg.com/marked/-/marked-0.6.2.tgz#c574be8b545a8b48641456ca1dbe0e37b6dccc1a"
-  integrity sha512-LqxwVH3P/rqKX4EKGz7+c2G9r98WeM/SW34ybhgNGhUQNKtf1GmmSkJ6cDGJ/t6tiyae49qRkpyTw2B9HOrgUA==
-
 marked@^0.7.0:
   version "0.7.0"
   resolved "https://registry.yarnpkg.com/marked/-/marked-0.7.0.tgz#b64201f051d271b1edc10a04d1ae9b74bb8e5c0e"
   integrity sha512-c+yYdCZJQrsRjTPhUx7VKkApw9bwDkNbHUKo1ovgcfDjb2kc8rLuRbIFyXL5WOEUwzSSKo3IXpph2K6DqB/KZg==
 
+marked@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/marked/-/marked-1.0.0.tgz#d35784245a04871e5988a491e28867362e941693"
+  integrity sha512-Wo+L1pWTVibfrSr+TTtMuiMfNzmZWiOPeO7rZsQUY5bgsxpHesBEcIWJloWVTFnrMXnf/TL30eTFSGJddmQAng==
+
 matchdep@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/matchdep/-/matchdep-2.0.0.tgz#c6f34834a0d8dbc3b37c27ee8bbcb27c7775582e"