fix: explicitly set an index for each API docs section (#732)

Author: andrewseguin

material.angular.io/src/app/pages/component-viewer/component-api.html

@@ -14,10 +14,10 @@
       (contentRendered)="updateTableOfContents(docItem!.name, $event)">
     </doc-viewer>
 
-    <doc-viewer *ngFor="let additionalApiDoc of docItem!.additionalApiDocs"
+    <doc-viewer *ngFor="let additionalApiDoc of docItem!.additionalApiDocs; let index = index"
       documentUrl="/docs-content/api-docs/{{additionalApiDoc.path}}"
       class="docs-component-view-text-content docs-component-api"
-      (contentRendered)="updateTableOfContents(additionalApiDoc.name, $event)">
+      (contentRendered)="updateTableOfContents(additionalApiDoc.name, $event, index + 1)">
     </doc-viewer>
   </span>
 

material.angular.io/src/app/pages/component-viewer/component-viewer.ts

@@ -99,9 +99,9 @@ export class ComponentBaseView implements OnInit, OnDestroy {
     this.destroyed.next();
   }
 
-  updateTableOfContents(sectionName: string, docViewerContent: HTMLElement) {
+  updateTableOfContents(sectionName: string, docViewerContent: HTMLElement, sectionIndex = 0) {
     if (this.tableOfContents) {
-      this.tableOfContents.addHeaders(sectionName, docViewerContent);
+      this.tableOfContents.addHeaders(sectionName, docViewerContent, sectionIndex);
       this.tableOfContents.updateScrollPosition();
     }
   }

material.angular.io/src/app/shared/table-of-contents/table-of-contents.ts

@@ -104,7 +104,7 @@ export class TableOfContents implements OnInit, AfterViewInit, OnDestroy {
     this._links = [];
   }
 
-  addHeaders(sectionName: string, docViewerContent: HTMLElement) {
+  addHeaders(sectionName: string, docViewerContent: HTMLElement, sectionIndex = 0) {
     const headers = Array.from<HTMLHeadingElement>(docViewerContent.querySelectorAll('h3, h4'));
     const links: Link[] = [];
     headers.forEach((header) => {
@@ -119,7 +119,7 @@ export class TableOfContents implements OnInit, AfterViewInit, OnDestroy {
         active: false
       });
     });
-    this._linkSections.push({name: sectionName, links});
+    this._linkSections[sectionIndex] = {name: sectionName, links};
     this._links.push(...links);
   }