platform/incubation/reflection/doc/capabilities.md

# Platform Reflection Capabilities

## Core Reflection Features

### 1. Library Reflection
```dart
// Library reflection support
final library = LibraryMirrorImpl.withDeclarations(
  name: 'my_library',
  uri: Uri.parse('package:my_package/my_library.dart'),
);

// Access top-level members
final greeting = library.getField(const Symbol('greeting')).reflectee;
final sum = library.invoke(
  const Symbol('add'),
  [1, 2],
).reflectee;
```

### 2. Isolate Support
```dart
// Current isolate reflection
final current = IsolateMirrorImpl.current(rootLibrary);

// Other isolate reflection
final other = IsolateMirrorImpl.other(
  isolate,
  'worker',
  rootLibrary,
);

// Isolate control
await other.pause();
await other.resume();
await other.kill();

// Error handling
other.addErrorListener((error, stack) {
  print('Error in isolate: $error\n$stack');
});

// Exit handling
other.addExitListener((message) {
  print('Isolate exited with: $message');
});
```

### 3. Type System
```dart
// Special types
final voidType = VoidType.instance;
final dynamicType = DynamicType.instance;
final neverType = NeverType.instance;

// Type checking
final isVoid = type.isVoid;
final isDynamic = type.isDynamic;
final isNever = type.isNever;
```

### 4. Metadata System
```dart
// Parameter metadata
final param = ParameterMetadata(
  name: 'id',
  type: int,
  isRequired: true,
  isNamed: false,
  defaultValue: 0,
  attributes: [deprecated],
);

// Property metadata
final prop = PropertyMetadata(
  name: 'name',
  type: String,
  isReadable: true,
  isWritable: true,
  attributes: [override],
);

// Method metadata
final method = MethodMetadata(
  name: 'calculate',
  parameterTypes: [int, double],
  parameters: [...],
  isStatic: false,
  returnsVoid: false,
  attributes: [deprecated],
);
```

### 5. Constructor Support
```dart
// Constructor metadata
final ctor = ConstructorMetadata(
  name: 'named',
  parameterTypes: [String, int],
  parameters: [...],
  parameterNames: ['name', 'age'],
  attributes: [...],
);

// Validation
final valid = ctor.validateArguments(['John', 42]);
```

### 6. Type Metadata
```dart
// Full type information
final type = TypeMetadata(
  type: User,
  name: 'User',
  properties: {...},
  methods: {...},
  constructors: [...],
  supertype: Person,
  interfaces: [Comparable],
  attributes: [serializable],
);

// Member access
final prop = type.getProperty('name');
final method = type.getMethod('greet');
final ctor = type.getConstructor('guest');
```

## Advanced Features

### 1. Library Dependencies
```dart
final deps = library.libraryDependencies;
for (var dep in deps) {
  if (dep.isImport) {
    print('Imports: ${dep.targetLibrary?.uri}');
  }
}
```

### 2. Declaration Access
```dart
final decls = library.declarations;
for (var decl in decls.values) {
  if (decl is MethodMirror) {
    print('Method: ${decl.simpleName}');
  } else if (decl is VariableMirror) {
    print('Variable: ${decl.simpleName}');
  }
}
```

### 3. Function Metadata
```dart
final func = FunctionMetadata(
  parameters: [...],
  returnsVoid: false,
  returnType: int,
);

final valid = func.validateArguments([1, 2.0]);
```

### 4. Reflection Registry
```dart
// Type registration
ReflectionRegistry.registerType(User);

// Member registration
ReflectionRegistry.registerProperty(
  User,
  'name',
  String,
  isReadable: true,
  isWritable: true,
);

ReflectionRegistry.registerMethod(
  User,
  'greet',
  [String],
  false,
);

ReflectionRegistry.registerConstructor(
  User,
  'guest',
  factory,
);
```

## Error Handling

```dart
try {
  // Reflection operations
} on MemberNotFoundException catch (e) {
  print('Member not found: ${e.memberName} on ${e.type}');
} on InvalidArgumentsException catch (e) {
  print('Invalid arguments for ${e.memberName}');
} on ReflectionException catch (e) {
  print('Reflection error: ${e.message}');
}
```

## Platform Support

- ✅ VM (Full support)
- ✅ Web (Full support)
- ✅ Flutter (Full support)
- ✅ AOT compilation (Full support)

## Performance Considerations

1. **Registration Impact**
   - One-time registration cost
   - Optimized runtime performance
   - Minimal memory overhead

2. **Metadata Caching**
   - Efficient metadata storage
   - Fast lookup mechanisms
   - Memory-conscious design

3. **Cross-isolate Performance**
   - Minimal serialization overhead
   - Efficient isolate communication
   - Controlled resource usage

## Security Features

1. **Access Control**
   - Controlled reflection surface
   - Explicit registration required
   - Member visibility respect

2. **Type Safety**
   - Strong type checking
   - Argument validation
   - Return type verification

3. **Isolate Safety**
   - Controlled isolate access
   - Error propagation
   - Resource cleanup

## Best Practices

1. **Registration**
   ```dart
   // Register early
   void main() {
     registerTypes();
     runApp();
   }
   ```

2. **Metadata Usage**
   ```dart
   // Cache metadata
   final metadata = Reflector.getTypeMetadata(User);
   final properties = metadata.properties;
   final methods = metadata.methods;
   ```

3. **Error Handling**
   ```dart
   // Comprehensive error handling
   try {
     final result = mirror.invoke(name, args);
   } on ReflectionException catch (e) {
     handleError(e);
   }
   ```

4. **Isolate Management**
   ```dart
   // Proper cleanup
   final isolate = IsolateMirrorImpl.other(...);
   try {
     await doWork(isolate);
   } finally {
     await isolate.kill();
   }
   ```

This document provides a comprehensive overview of the Platform Reflection library's capabilities. For detailed API documentation, see the [API Reference](../README.md#api-reference).