fix(docs-infra): do not process generated nodes for auto-linking (#41709)

While generating the docs, when a `<code>` element is inspected for
auto-linking, the `autoLinkCode` Dgeni post-processor will break its
contents up into words and generate text nodes for those words that
should not be auto-linked.

Previously, our text node visitor would visit these generated text nodes
and try to auto-link them too. As a result, it would unnecessarily
process nodes that had already been checked (and could potentially
generate links that would otherwise be ignored).

You can see an occurrence of this issue in the
[Create the product list][1] section of the
"Getting started with Angular" tutorial (look for `<a>`).

This commit fixes this by ensuring the visitor will skip the current
node and any nodes generated by `autoLinkCode`.

[1]: https://v11.angular.io/start#create-the-product-list

PR Close #41709

aio/tools/transforms/angular-base-package/post-processors/auto-link-code.js

@@ -63,6 +63,8 @@ module.exports = function autoLinkCode(getDocFromAlias) {
             const nodes = getNodes(node, file);
             // Replace the text node with the links and leftover text nodes
             Array.prototype.splice.apply(parent.children, [index, 1].concat(nodes));
+            // Do not visit this node's children or the newly added nodes
+            return [visit.SKIP, index + nodes.length];
           }
         });
       });

aio/tools/transforms/angular-base-package/post-processors/auto-link-code.spec.js

@@ -110,11 +110,32 @@ describe('autoLinkCode post-processor', () => {
             '{ xyz | <a href="a/b/myclass" class="code-anchor">myClass</a> } ' +
             '{ xyz|<a href="a/b/myclass" class="code-anchor">myClass</a> } ' +
             '<a href="a/b/myclass" class="code-anchor">MyClass</a> ' +
-            '<a href="a/b/myclass" class="code-anchor">myClass</a> ' +
+            'myClass ' +
             'OtherClass|<a href="a/b/myclass" class="code-anchor">MyClass</a>' +
             '</code>');
   });
 
+  it('should ignore generated nodes', () => {
+    const filterAnchors = (docs, words, index) => (words[index].toLowerCase() === 'a') ? [] : docs;
+    autoLinkCode.customFilters = [filterAnchors];
+    autoLinkCode.docTypes = ['directive'];
+
+    aliasMap.addDoc({
+      docType: 'directive',
+      id: 'MyAnchorDirective',
+      aliases: ['MyAnchorDirective', 'a'],
+      path: 'a/b/my-anchor-directive',
+    });
+    const doc = {
+      docType: 'test-doc',
+      renderedContent: '<code>&#x3C;a></code>',
+    };
+
+    processor.$process([doc]);
+
+    expect(doc.renderedContent).toBe('<code>&#x3C;a></code>');
+  });
+
   it('should ignore code items that match an internal API doc', () => {
     aliasMap.addDoc({
       docType: 'class',