feat(ivy): do not emit empty providers/imports for defineInjector (#29598)

The defineInjector function specifies its providers and imports array to
be optional, so if no providers/imports are present these keys may be
omitted. This commit updates the compiler to only generate the keys when
necessary.

PR Close #29598

packages/compiler-cli/src/ngtsc/annotations/src/ng_module.ts

@@ -158,10 +158,8 @@ export class NgModuleDecoratorHandler implements DecoratorHandler<NgModuleAnalys
       schemas: [],
     };
 
-    const providers: Expression = ngModule.has('providers') ?
-        new WrappedNodeExpr(ngModule.get('providers') !) :
-        new LiteralArrayExpr([]);
     const rawProviders = ngModule.has('providers') ? ngModule.get('providers') ! : null;
+    const providers = rawProviders !== null ? new WrappedNodeExpr(rawProviders) : null;
 
     // At this point, only add the module's imports as the injectors' imports. Any exported modules
     // are added during `resolve`, as we need scope information to be able to filter out directives

packages/compiler-cli/test/ngtsc/ngtsc_spec.ts

@@ -445,6 +445,10 @@ describe('ngtsc behavioral tests', () => {
     expect(jsContents).toContain('i0.ɵdefineNgModule({ type: TestModule, bootstrap: [TestCmp] });');
     expect(jsContents)
         .toContain('/*@__PURE__*/ i0.ɵsetNgModuleScope(TestModule, { declarations: [TestCmp] });');
+    expect(jsContents)
+        .toContain(
+            'i0.defineInjector({ factory: ' +
+            'function TestModule_Factory(t) { return new (t || TestModule)(); } });');
 
     const dtsContents = env.getContents('test.d.ts');
     expect(dtsContents)
@@ -528,8 +532,8 @@ describe('ngtsc behavioral tests', () => {
     expect(jsContents)
         .toContain(
             'i0.defineInjector({ factory: function TestModule_Factory(t) ' +
-            '{ return new (t || TestModule)(); }, providers: [], ' +
-            'imports: [[OtherModule, RouterModule.forRoot()],\n            OtherModule,\n            RouterModule] });');
+            '{ return new (t || TestModule)(); }, imports: [[OtherModule, RouterModule.forRoot()],' +
+            '\n            OtherModule,\n            RouterModule] });');
   });
 
   it('should compile NgModules with services without errors', () => {

packages/compiler/src/render3/r3_module_compiler.ts

@@ -190,7 +190,7 @@ export interface R3InjectorMetadata {
   name: string;
   type: o.Expression;
   deps: R3DependencyMetadata[]|null;
-  providers: o.Expression;
+  providers: o.Expression|null;
   imports: o.Expression[];
 }
 
@@ -201,11 +201,19 @@ export function compileInjector(meta: R3InjectorMetadata): R3InjectorDef {
     deps: meta.deps,
     injectFn: R3.inject,
   });
-  const expression = o.importExpr(R3.defineInjector).callFn([mapToMapExpression({
+  const definitionMap = {
     factory: result.factory,
-    providers: meta.providers,
-    imports: o.literalArr(meta.imports),
-  })]);
+  } as{factory: o.Expression, providers: o.Expression, imports: o.Expression};
+
+  if (meta.providers !== null) {
+    definitionMap.providers = meta.providers;
+  }
+
+  if (meta.imports.length > 0) {
+    definitionMap.imports = o.literalArr(meta.imports);
+  }
+
+  const expression = o.importExpr(R3.defineInjector).callFn([mapToMapExpression(definitionMap)]);
   const type =
       new o.ExpressionType(o.importExpr(R3.InjectorDef, [new o.ExpressionType(meta.type)]));
   return {expression, type, statements: result.statements};