fix(@angular-devkit/build-optimizer): don't search for pure top-level functions inside classes

Partially address #816.

Supersedes #237

Author: filipesilva

Diff for: packages/angular_devkit/build_optimizer/src/transforms/prefix-functions.ts

@@ -53,8 +53,11 @@ export function findTopLevelFunctions(parentNode: ts.Node): Set<ts.Node> {
   const topLevelFunctions = new Set<ts.Node>();
 
   function cb(node: ts.Node) {
-    // Stop recursing into this branch if it's a function expression or declaration
-    if (ts.isFunctionDeclaration(node) || ts.isFunctionExpression(node)) {
+    // Stop recursing into this branch if it's a function expression or declaration, or a class.
+    if (ts.isFunctionDeclaration(node)
+      || ts.isFunctionExpression(node)
+      || ts.isClassDeclaration(node)
+    ) {
       return;
     }
 

Diff for: packages/angular_devkit/build_optimizer/src/transforms/prefix-functions_spec.ts

@@ -124,5 +124,24 @@ describe('prefix-functions', () => {
 
       expect(tags.oneLine`${transform(input)}`).toEqual(tags.oneLine`${output}`);
     });
+
+    it('doesn\'t add comment when inside class', () => {
+      const input = tags.stripIndent`
+        class Foo {
+          constructor(e) {
+            super(e);
+          }
+          method() {
+            var newClazz = new Clazz();
+          }
+        }
+      `;
+      const output = tags.stripIndent`
+        ${emptyImportsComment}
+        ${input}
+      `;
+
+      expect(tags.oneLine`${transform(input)}`).toEqual(tags.oneLine`${output}`);
+    });
   });
 });