build(aio): automatically link code blocks to API docs

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

@@ -0,0 +1,36 @@
+const visit = require('unist-util-visit');
+const is = require('hast-util-is-element');
+const textContent = require('hast-util-to-string');
+
+/**
+ * Automatically add in a link to the relevant document for simple
+ * code blocks, e.g. `<code>MyClass</code>` becomes
+ * `<code><a href="path/to/myclass">MyClass</a></code>`
+ *
+ * @property docTypes an array of strings. Only docs that have one of these docTypes
+ * will be linked to.
+ * Usually set to the API exported docTypes, e.g. "class", "function", "directive", etc.
+ */
+module.exports = function autoLinkCode(getDocFromAlias) {
+  autoLinkCodeImpl.docTypes = [];
+  return autoLinkCodeImpl;
+
+  function autoLinkCodeImpl()  {
+    return (ast) => {
+      visit(ast, node => {
+        if (is(node, 'code')) {
+          const docs = getDocFromAlias(textContent(node));
+          if (docs.length === 1 && autoLinkCodeImpl.docTypes.indexOf(docs[0].docType) !== -1) {
+            const link = {
+              type: 'element',
+              tagName: 'a',
+              properties: { href: docs[0].path },
+              children: node.children
+            };
+            node.children = [link];
+          }
+        }
+      });
+    };
+  }
+};