@GenerateMocks fails with NavigatorState

[Pante]

An error is thrown when generating a mock for Flutter's NavigatorState.

import 'package:flutter/widgets.dart';

@GenerateMocks([NavigatorState])
void main() {}

Running flutter pub build_runner build -v with the above code snippet leads to the following error:

[  +66 ms] executing: [C:\Users\Matthias\Documents\flutter/] git -c log.showSignature=false log -n 1 --pretty=format:%H
[ +408 ms] Exit code 0 from: git -c log.showSignature=false log -n 1 --pretty=format:%H
[   +1 ms] d79295af24c3ed621c33713ecda14ad196fd9c31
[   +1 ms] executing: [C:\Users\Matthias\Documents\flutter/] git tag --points-at d79295af24c3ed621c33713ecda14ad196fd9c31
[  +52 ms] Exit code 0 from: git tag --points-at d79295af24c3ed621c33713ecda14ad196fd9c31
[        ] 2.2.2
[   +5 ms] executing: [C:\Users\Matthias\Documents\flutter/] git rev-parse --abbrev-ref --symbolic @{u}
[  +48 ms] Exit code 0 from: git rev-parse --abbrev-ref --symbolic @{u}
[        ] origin/stable
[        ] executing: [C:\Users\Matthias\Documents\flutter/] git ls-remote --get-url origin
[  +44 ms] Exit code 0 from: git ls-remote --get-url origin
[        ] https://github.com/flutter/flutter.git
[ +119 ms] executing: [C:\Users\Matthias\Documents\flutter/] git rev-parse --abbrev-ref HEAD
[  +52 ms] Exit code 0 from: git rev-parse --abbrev-ref HEAD
[        ] stable
[  +72 ms] Artifact Instance of 'AndroidGenSnapshotArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'AndroidInternalBuildArtifacts' is not required, skipping update.
[   +1 ms] Artifact Instance of 'IOSEngineArtifacts' is not required, skipping update.
[   +1 ms] Artifact Instance of 'FlutterWebSdk' is not required, skipping update.
[   +3 ms] Artifact Instance of 'WindowsEngineArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'MacOSEngineArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'LinuxEngineArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'LinuxFuchsiaSDKArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'MacOSFuchsiaSDKArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'FlutterRunnerSDKArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'FlutterRunnerDebugSymbols' is not required, skipping update.
[  +50 ms] Artifact Instance of 'MaterialFonts' is not required, skipping update.
[        ] Artifact Instance of 'GradleWrapper' is not required, skipping update.
[        ] Artifact Instance of 'AndroidGenSnapshotArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'AndroidInternalBuildArtifacts' is not required, skipping update.
[   +1 ms] Artifact Instance of 'IOSEngineArtifacts' is not required, skipping update.
[   +1 ms] Artifact Instance of 'FlutterWebSdk' is not required, skipping update.
[        ] Artifact Instance of 'FlutterSdk' is not required, skipping update.
[        ] Artifact Instance of 'WindowsEngineArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'MacOSEngineArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'LinuxEngineArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'LinuxFuchsiaSDKArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'MacOSFuchsiaSDKArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'FlutterRunnerSDKArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'FlutterRunnerDebugSymbols' is not required, skipping update.
[        ] Artifact Instance of 'IosUsbArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'IosUsbArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'IosUsbArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'IosUsbArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'IosUsbArtifacts' is not required, skipping update.
[        ] Artifact Instance of 'FontSubsetArtifacts' is not required, skipping update.
[   +1 ms] Artifact Instance of 'PubDependencies' is not required, skipping update.
[  +26 ms] Using C:\Users\Matthias\Documents\flutter\.pub-cache for the pub cache.
[        ] executing: C:\Users\Matthias\Documents\flutter\bin\cache\dart-sdk\bin\pub run build_runner build -v
[INFO] Entrypoint:Generating build script...
[INFO] Entrypoint:Generating build script completed, took 456ms

[INFO] BuildDefinition:Initializing inputs
[INFO] BuildDefinition:Reading cached asset graph...
[INFO] BuildDefinition:Reading cached asset graph completed, took 53ms

[INFO] BuildDefinition:Checking for updates since last build...
[INFO] BuildDefinition:Checking for updates since last build completed, took 598ms

[INFO] Build:Running build...
[INFO] Build:Running build completed, took 10ms

[INFO] Build:Caching finalized dependency graph...
[INFO] Build:Caching finalized dependency graph completed, took 37ms

[SEVERE] mockito:mockBuilder on test/keyed_test.dart (cached):

Null check operator used on a null value
package:mockito/src/builder.dart 1464:30                     _MockLibraryInfo._typeImport
package:mockito/src/builder.dart 1403:19                     _MockLibraryInfo._typeReference.<fn>
package:code_builder/src/specs/type_reference.g.dart 160:33  _$TypeReferenceBuilder.update
package:code_builder/src/specs/type_reference.g.dart 22:36   new _$TypeReference
package:mockito/src/builder.dart 1399:14                     _MockLibraryInfo._typeReference
package:mockito/src/builder.dart 1214:18                     _MockLibraryInfo._matchingParameter.<fn>
package:code_builder/src/specs/method.g.dart 641:33          _$ParameterBuilder.update
package:code_builder/src/specs/method.g.dart 403:32          new _$Parameter
package:mockito/src/builder.dart 1211:12                     _MockLibraryInfo._matchingParameter
package:mockito/src/builder.dart 967:18                      _MockLibraryInfo._buildOverridingMethod
package:mockito/src/builder.dart 1190:27                     _MockLibraryInfo._addFakeClass.<fn>.<fn>
package:code_builder/src/specs/method.g.dart 332:33          _$MethodBuilder.update
package:code_builder/src/specs/method.g.dart 38:29           new _$Method
package:mockito/src/builder.dart 1189:30                     _MockLibraryInfo._addFakeClass.<fn>
package:code_builder/src/specs/class.g.dart 292:33           _$ClassBuilder.update
package:code_builder/src/specs/class.g.dart 34:28            new _$Class
package:mockito/src/builder.dart 1163:21                     _MockLibraryInfo._addFakeClass
package:mockito/src/builder.dart 1150:9                      _MockLibraryInfo._dummyValueImplementing
package:mockito/src/builder.dart 1097:12                     _MockLibraryInfo._dummyValue
package:mockito/src/builder.dart 1000:24                     _MockLibraryInfo._buildOverridingMethod
package:mockito/src/builder.dart 887:36                      _MockLibraryInfo.methodOverrides.<fn>
package:code_builder/src/specs/method.g.dart 332:33          _$MethodBuilder.update
package:code_builder/src/specs/method.g.dart 38:29           new _$Method
package:mockito/src/builder.dart 887:15                      _MockLibraryInfo.methodOverrides
dart:core                                                    List.addAll
package:built_collection/src/list/list_builder.dart 98:14    ListBuilder.addAll
package:mockito/src/builder.dart 807:24                      _MockLibraryInfo._buildMockClass.<fn>
package:code_builder/src/specs/class.g.dart 292:33           _$ClassBuilder.update
package:code_builder/src/specs/class.g.dart 34:28            new _$Class
package:mockito/src/builder.dart 753:12                      _MockLibraryInfo._buildMockClass
package:mockito/src/builder.dart 743:23                      new _MockLibraryInfo
package:mockito/src/builder.dart 65:29                       MockBuilder.build

[SEVERE] Build:
Failed after 85ms
[+2861 ms] "flutter run" took 2,964ms.
[   +8 ms] pub finished with exit code 1
[   +3 ms] 
           #0      throwToolExit (package:flutter_tools/src/base/common.dart:10:3)
           #1      _DefaultPub.interactively (package:flutter_tools/src/dart/pub.dart:368:7)
           <asynchronous suspension>
           #2      PackagesForwardCommand.runCommand (package:flutter_tools/src/commands/packages.dart:241:5)
           <asynchronous suspension>
           #3      FlutterCommand.run.<anonymous closure> (package:flutter_tools/src/runner/flutter_command.dart:1043:27)
           <asynchronous suspension>
           #4      AppContext.run.<anonymous closure> (package:flutter_tools/src/base/context.dart:150:19)
           <asynchronous suspension>
           #5      CommandRunner.runCommand (package:args/command_runner.dart:196:13)
           <asynchronous suspension>
           #6      FlutterCommandRunner.runCommand.<anonymous closure> (package:flutter_tools/src/runner/flutter_command_runner.dart:284:9)
           <asynchronous suspension>
           #7      AppContext.run.<anonymous closure> (package:flutter_tools/src/base/context.dart:150:19)
           <asynchronous suspension>
           #8      FlutterCommandRunner.runCommand (package:flutter_tools/src/runner/flutter_command_runner.dart:232:5)
           <asynchronous suspension>
           #9      run.<anonymous closure>.<anonymous closure> (package:flutter_tools/runner.dart:62:9)
           <asynchronous suspension>
           #10     AppContext.run.<anonymous closure> (package:flutter_tools/src/base/context.dart:150:19)
           <asynchronous suspension>
           #11     main (package:flutter_tools/executable.dart:91:3)
           <asynchronous suspension>
           
           
[  +69 ms] ensureAnalyticsSent: 65ms
[   +2 ms] Running shutdown hooks
[        ] Shutdown hooks complete
[        ] exiting with code 1

[srawlins]

Thanks for the report! I've figured out that this is because:

• NavigatorState implements State
• State has toDiagnosticsNode which returns a non-nullable DiagnosticsNode, so we need to make a _FakeDiagnosticsNode,
• DiagnosticsNode overrides toString with an optional named parameter with type TextTreeConfiguration, so we need to refer to that class, but miss it.