fix(@angular-devkit/build-angular): account for arrow function IIFE

Updates the logic for removing Angular metadata and pure top-level functions to account for arrow-function-based IIFEs. Currently Angular doesn't generate arrow functions, but it's being explored in angular/angular#51637.

Author: crisbeto

packages/angular_devkit/build_angular/src/tools/babel/plugins/elide-angular-metadata.ts

@@ -58,13 +58,13 @@ export default function (): PluginObj {
         }
 
         // The metadata function is always emitted inside a function expression
-        if (!path.getFunctionParent()?.isFunctionExpression()) {
-          return;
-        }
+        const parent = path.getFunctionParent();
 
-        // Replace the metadata function with `void 0` which is the equivalent return value
-        // of the metadata function.
-        path.replaceWith(path.scope.buildUndefinedNode());
+        if (parent && (parent.isFunctionExpression() || parent.isArrowFunctionExpression())) {
+          // Replace the metadata function with `void 0` which is the equivalent return value
+          // of the metadata function.
+          path.replaceWith(path.scope.buildUndefinedNode());
+        }
       },
     },
   };

packages/angular_devkit/build_angular/src/tools/babel/plugins/elide-angular-metadata_spec.ts

@@ -79,4 +79,27 @@ describe('elide-angular-metadata Babel plugin', () => {
         (function () { (typeof ngJitMode === "undefined" || ngJitMode) && void 0 })();`,
     }),
   );
+
+  it(
+    'elides ɵsetClassMetadata inside an arrow-function-based IIFE',
+    testCase({
+      input: `
+        import { Component } from '@angular/core';
+        export class SomeClass {}
+        /*@__PURE__*/ (() => { i0.ɵsetClassMetadata(Clazz, [{
+            type: Component,
+            args: [{
+                    selector: 'app-lazy',
+                    template: 'very lazy',
+                    styles: []
+                }]
+        }], null, null); })();
+      `,
+      expected: `
+        import { Component } from '@angular/core';
+        export class SomeClass {}
+        /*@__PURE__*/ (() => { void 0 })();
+      `,
+    }),
+  );
 });

packages/angular_devkit/build_angular/src/tools/babel/plugins/pure-toplevel-functions.ts

@@ -47,7 +47,10 @@ export default function (): PluginObj {
         }
 
         const callee = path.node.callee;
-        if (types.isFunctionExpression(callee) && path.node.arguments.length !== 0) {
+        if (
+          (types.isFunctionExpression(callee) || types.isArrowFunctionExpression(callee)) &&
+          path.node.arguments.length !== 0
+        ) {
           return;
         }
         // Do not annotate TypeScript helpers emitted by the TypeScript compiler.

packages/angular_devkit/build_angular/src/tools/babel/plugins/pure-toplevel-functions_spec.ts

@@ -65,13 +65,29 @@ describe('pure-toplevel-functions Babel plugin', () => {
     }),
   );
 
+  it(
+    'annotates top-level arrow-function-based IIFE assignments with no arguments',
+    testCase({
+      input: 'var SomeClass = (() => { function SomeClass() { } return SomeClass; })();',
+      expected:
+        'var SomeClass = /*#__PURE__*/(() => { function SomeClass() { } return SomeClass; })();',
+    }),
+  );
+
   it(
     'does not annotate top-level IIFE assignments with arguments',
     testCaseNoChange(
       'var SomeClass = (function () { function SomeClass() { } return SomeClass; })(abc);',
     ),
   );
 
+  it(
+    'does not annotate top-level arrow-function-based IIFE assignments with arguments',
+    testCaseNoChange(
+      'var SomeClass = (() => { function SomeClass() { } return SomeClass; })(abc);',
+    ),
+  );
+
   it(
     'does not annotate call expressions inside function declarations',
     testCaseNoChange('function funcDecl() { const result = someFunction(); }'),