build: build material-examples with bazel (#13932)

This includes a `genrule` to create the generated `ExampleModule`

tools/example-module/parse-example-file.ts

@@ -0,0 +1,75 @@
+import * as ts from 'typescript';
+
+interface ParsedMetadata {
+  primary: boolean;
+  component: string;
+  title: string;
+  templateUrl: string;
+  styleUrls: string[];
+}
+
+interface ParsedMetadataResults {
+  primaryComponent: ParsedMetadata;
+  secondaryComponents: ParsedMetadata[];
+}
+
+/** Parse the AST of the given source file and collect Angular component metadata. */
+export function parseExampleFile(fileName: string, content: string): ParsedMetadataResults {
+  const sourceFile = ts.createSourceFile(fileName, content, ts.ScriptTarget.Latest, false);
+  const metas: any[] = [];
+
+  const visitNode = (node: any): void => {
+    if (node.kind === ts.SyntaxKind.ClassDeclaration) {
+      const meta: any = {
+        component: node.name.text
+      };
+
+      if (node.jsDoc && node.jsDoc.length) {
+        for (const doc of node.jsDoc) {
+          if (doc.tags && doc.tags.length) {
+            for (const tag of doc.tags) {
+              const tagValue = tag.comment;
+              const tagName = tag.tagName.text;
+              if (tagName === 'title') {
+                meta.title = tagValue;
+                meta.primary = true;
+              }
+            }
+          }
+        }
+      }
+
+      if (node.decorators && node.decorators.length) {
+        for (const decorator of node.decorators) {
+          if (decorator.expression.expression.text === 'Component') {
+            for (const arg of decorator.expression.arguments) {
+              for (const prop of arg.properties) {
+                const propName = prop.name.text;
+
+                // Since additional files can be also stylesheets, we need to properly parse
+                // the styleUrls metadata property.
+                if (propName === 'styleUrls' && ts.isArrayLiteralExpression(prop.initializer)) {
+                  meta[propName] = prop.initializer.elements
+                    .map((literal: ts.StringLiteral) => literal.text);
+                } else {
+                  meta[propName] = prop.initializer.text;
+                }
+              }
+            }
+
+            metas.push(meta);
+          }
+        }
+      }
+    }
+
+    ts.forEachChild(node, visitNode);
+  };
+
+  visitNode(sourceFile);
+
+  return {
+    primaryComponent: metas.find(m => m.primary),
+    secondaryComponents: metas.filter(m => !m.primary)
+  };
+}