fix(Compiler): Refuse invalid function (null) in FactoryProvider.

Turns a (mysterious) runtime error into a compile-time one. Shouldn't impact users.

Closes #1500.
Closes #1581.

PiperOrigin-RevId: 209173141

_tests/build.debug.yaml

@@ -16,6 +16,7 @@ targets:
           - test/core/di/provider_test.dart*
           - test/regression/906_incorrect_injectable_warning_test.dart*
           - test/regression/519_missing_query_selector_test.dart*
+          - test/regression/1500_factory_provider_null_test.dart*
           - test/regression/1538_deferred_template_test.dart*
 
       angular:

_tests/build.yaml

@@ -12,6 +12,7 @@ targets:
           - test/core/di/provider_test.dart*
           - test/regression/906_incorrect_injectable_warning_test.dart*
           - test/regression/519_missing_query_selector_test.dart*
+          - test/regression/1500_factory_provider_null_test.dart*
           - test/regression/1538_deferred_template_test.dart*
       angular:
         options:

_tests/test/regression/1500_factory_provider_null_test.dart

@@ -0,0 +1,21 @@
+@TestOn('vm')
+import 'package:_tests/compiler.dart';
+import 'package:test/test.dart';
+
+// See https://github.com/dart-lang/angular/issues/1500.
+void main() {
+  test('should disallow a value of "null" for FactoryProvider', () async {
+    await compilesExpecting("""
+      import '$ngImport';
+
+      class Service {}
+
+      @GenerateInjector([
+        FactoryProvider(Service, null),
+      ])
+      final InjectorFactory injectorFactory = null; // OK for compiler tests.
+    """, errors: [
+      contains('an explicit value of `null` was passed in where a function is'),
+    ]);
+  });
+}

angular/CHANGELOG.md

@@ -63,8 +63,12 @@
     `*ngFor="let item of items;"` - note the trailing `;`), throws a proper
     unexpected token error instead of a confusing type error during recovery.
 
+*   [#1500][]: Configuring a provider with `FactoryProvider(Foo, null)` is now
+    a compile-time error, instead of a misleading runtime error.
+
 [#434]: https://github.com/dart-lang/angular/issues/434
 [#880]: https://github.com/dart-lang/angular/issues/880
+[#1500]: https://github.com/dart-lang/angular/issues/1500
 [#1502]: https://github.com/dart-lang/angular/issues/1502
 [#1538]: https://github.com/dart-lang/angular/issues/1538
 [#1539]: https://github.com/dart-lang/angular/issues/1539

angular_compiler/CHANGELOG.md

@@ -1,5 +1,7 @@
 *   Catches an (invalid) `null` token of a provider and throws a better error.
 
+*   Catches an (invalid) `null` value of the function for `FactoryProvider`.
+
 ## 0.4.0
 
 ### New Features

angular_compiler/lib/src/analyzer/di/injector.dart

@@ -84,6 +84,14 @@ class InjectorReader {
     );
   }
 
+  @alwaysThrows
+  void _throwFactoryProvider(DartObject context) {
+    BuildError.throwForElement(
+        field,
+        'Invalid provider ($context): an explicit value of `null` was passed in '
+        'where a function is expected.');
+  }
+
   /// Providers that are part of the provided list of the annotation.
   Iterable<ProviderElement> get providers {
     if (_providers == null) {
@@ -96,6 +104,8 @@ class InjectorReader {
         _providers = moduleReader.deduplicateProviders(module.flatten());
       } on NullTokenException catch (e) {
         _throwParseError(e.constant);
+      } on NullFactoryException catch (e) {
+        _throwFactoryProvider(e.constant);
       }
     }
     return _providers;

angular_compiler/lib/src/analyzer/di/providers.dart

@@ -36,7 +36,6 @@ class ProviderReader {
     }
     if (isType(o)) {
       // Represents "Foo", which is supported short-hand for "Provider(Foo)".
-      // TODO(matanl): Validate that Foo has @Injectable() when flag is set.
       return _parseType(o);
     }
     if (!isProvider(o)) {
@@ -50,7 +49,7 @@ class ProviderReader {
     final reader = ConstantReader(o);
     final value = reader.read('token');
     if (value.isNull) {
-      throw new NullTokenException(o);
+      throw NullTokenException(o);
     }
     final token = _tokenReader.parseTokenObject(value.objectValue);
     final useClass = reader.read('useClass');
@@ -81,6 +80,11 @@ class ProviderReader {
     }
     // Base case: const Provider(Foo) with no fields set.
     if (token is TypeTokenElement) {
+      // Ensure this isn't a FactoryProvider with a null function:
+      // https://github.com/dart-lang/angular/issues/1500
+      if (!$Provider.isExactlyType(o.type)) {
+        throw NullFactoryException(o);
+      }
       return _parseUseClass(token, o, reader.read('token').typeValue.element);
     }
     throw UnsupportedError('Could not parse provider: $o.');
@@ -338,3 +342,11 @@ class NullTokenException implements Exception {
 
   const NullTokenException(this.constant);
 }
+
+/// Thrown when a value of `null` is read for `FactoryProvider`.
+class NullFactoryException implements Exception {
+  /// Constant whose `.token` property was resolved to `null`.
+  final DartObject constant;
+
+  const NullFactoryException(this.constant);
+}