Code generation for ObjC protocols (#1175)

Author: liamappelbe

pkgs/ffigen/CHANGELOG.md

@@ -23,6 +23,8 @@
   To silence the warning set config `silence-enum-warning` to `true`.
 - Rename ObjC interface methods that clash with type names. Fixes
   https://github.com/dart-lang/native/issues/1007.
+- Added support for implementing ObjC protocols from Dart. Use the
+  `objc-protocols` config option to generate bindings for a protocol.
 
 ## 12.0.0
 

pkgs/ffigen/README.md

@@ -666,11 +666,12 @@ import:
 <tbody>
   <tr>
     <td>
-      objc-interfaces
+      objc-interfaces<br><br>objc-protocols
     </td>
     <td>
-      Filters for interface declarations. This option works the same as other
-      declaration filters like `functions` and `structs`.
+      Filters for Objective C interface and protocol declarations. This option
+      works the same as other declaration filters like `functions` and
+      `structs`.
     </td>
     <td>
 
@@ -687,17 +688,21 @@ objc-interfaces:
   rename:
     # Removes '_' prefix from interface names.
     '_(.*)': '$1'
+objc-protocols:
+  include:
+    # Generates bindings for a specific protocol.
+    - MyProtocol
 ```
 
   </td>
   </tr>
 
   <tr>
     <td>
-      objc-interfaces -> module
+      objc-interfaces -> module<br><br>objc-protocols -> module
     </td>
     <td>
-      Adds a module prefix to the class name when loading the class
+      Adds a module prefix to the interface/protocol name when loading it
       from the dylib. This is only relevent for ObjC headers that are generated
       wrappers for a Swift library. See example/swift for more information.
     </td>

pkgs/ffigen/ffigen.schema.json

@@ -333,7 +333,28 @@
           "$ref": "#/$defs/memberRename"
         },
         "module": {
-          "$ref": "#/$defs/objcInterfaceModule"
+          "$ref": "#/$defs/objcModule"
+        }
+      }
+    },
+    "objc-protocols": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "include": {
+          "$ref": "#/$defs/fullMatchOrRegexpList"
+        },
+        "exclude": {
+          "$ref": "#/$defs/fullMatchOrRegexpList"
+        },
+        "rename": {
+          "$ref": "#/$defs/rename"
+        },
+        "member-rename": {
+          "$ref": "#/$defs/memberRename"
+        },
+        "module": {
+          "$ref": "#/$defs/objcModule"
         }
       }
     },
@@ -495,7 +516,7 @@
         "opaque"
       ]
     },
-    "objcInterfaceModule": {
+    "objcModule": {
       "type": "object",
       "patternProperties": {
         ".*": {

pkgs/ffigen/lib/src/code_generator.dart

@@ -19,7 +19,9 @@ export 'code_generator/native_type.dart';
 export 'code_generator/objc_block.dart';
 export 'code_generator/objc_built_in_functions.dart';
 export 'code_generator/objc_interface.dart';
+export 'code_generator/objc_methods.dart';
 export 'code_generator/objc_nullable.dart';
+export 'code_generator/objc_protocol.dart';
 export 'code_generator/pointer.dart';
 export 'code_generator/struct.dart';
 export 'code_generator/type.dart';

pkgs/ffigen/lib/src/code_generator/binding_string.dart

@@ -24,5 +24,6 @@ enum BindingStringType {
   enum_,
   typeDef,
   objcInterface,
+  objcProtocol,
   objcBlock,
 }

pkgs/ffigen/lib/src/code_generator/compound.dart

@@ -34,6 +34,8 @@ abstract class Compound extends BindingType {
   bool get isStruct => compoundType == CompoundType.struct;
   bool get isUnion => compoundType == CompoundType.union;
 
+  ObjCBuiltInFunctions? objCBuiltInFunctions;
+
   Compound({
     super.usr,
     super.originalName,
@@ -44,6 +46,7 @@ abstract class Compound extends BindingType {
     super.dartDoc,
     List<Member>? members,
     super.isInternal,
+    this.objCBuiltInFunctions,
   }) : members = members ?? [];
 
   factory Compound.fromType({
@@ -55,6 +58,7 @@ abstract class Compound extends BindingType {
     int? pack,
     String? dartDoc,
     List<Member>? members,
+    required ObjCBuiltInFunctions objCBuiltInFunctions,
   }) {
     switch (type) {
       case CompoundType.struct:
@@ -66,6 +70,7 @@ abstract class Compound extends BindingType {
           pack: pack,
           dartDoc: dartDoc,
           members: members,
+          objCBuiltInFunctions: objCBuiltInFunctions,
         );
       case CompoundType.union:
         return Union(
@@ -76,6 +81,7 @@ abstract class Compound extends BindingType {
           pack: pack,
           dartDoc: dartDoc,
           members: members,
+          objCBuiltInFunctions: objCBuiltInFunctions,
         );
     }
   }
@@ -88,8 +94,17 @@ abstract class Compound extends BindingType {
     return type.getCType(w);
   }
 
+  bool get _isBuiltIn =>
+      objCBuiltInFunctions?.isBuiltInInterface(originalName) ?? false;
+
   @override
   BindingString toBindingString(Writer w) {
+    final bindingType =
+        isStruct ? BindingStringType.struct : BindingStringType.union;
+    if (_isBuiltIn) {
+      return BindingString(type: bindingType, string: '');
+    }
+
     final s = StringBuffer();
     final enclosingClassName = name;
     if (dartDoc != null) {
@@ -135,14 +150,12 @@ abstract class Compound extends BindingType {
     }
     s.write('}\n\n');
 
-    return BindingString(
-        type: isStruct ? BindingStringType.struct : BindingStringType.union,
-        string: s.toString());
+    return BindingString(type: bindingType, string: s.toString());
   }
 
   @override
   void addDependencies(Set<Binding> dependencies) {
-    if (dependencies.contains(this)) return;
+    if (dependencies.contains(this) || _isBuiltIn) return;
 
     dependencies.add(this);
     for (final m in members) {
@@ -154,7 +167,7 @@ abstract class Compound extends BindingType {
   bool get isIncompleteCompound => isIncomplete;
 
   @override
-  String getCType(Writer w) => name;
+  String getCType(Writer w) => _isBuiltIn ? '${w.objcPkgPrefix}.$name' : name;
 
   @override
   String getNativeType({String varName = ''}) => '$originalName $varName';

pkgs/ffigen/lib/src/code_generator/objc_block.dart

@@ -4,26 +4,37 @@
 
 import 'package:ffigen/src/code_generator.dart';
 import 'package:ffigen/src/config_provider/config_types.dart';
+import 'package:ffigen/src/header_parser/data.dart' show bindingsIndex;
 
 import 'binding_string.dart';
 import 'writer.dart';
 
 class ObjCBlock extends BindingType {
   final Type returnType;
   final List<Type> argTypes;
-
   Func? _wrapListenerBlock;
 
-  ObjCBlock({
-    required String usr,
+  factory ObjCBlock({
     required Type returnType,
     required List<Type> argTypes,
-  }) : this._(
-          usr: usr,
-          name: _getBlockName(returnType, argTypes),
-          returnType: returnType,
-          argTypes: argTypes,
-        );
+  }) {
+    final usr = _getBlockUsr(returnType, argTypes);
+
+    final oldBlock = bindingsIndex.getSeenObjCBlock(usr);
+    if (oldBlock != null) {
+      return oldBlock;
+    }
+
+    final block = ObjCBlock._(
+      usr: usr,
+      name: _getBlockName(returnType, argTypes),
+      returnType: returnType,
+      argTypes: argTypes,
+    );
+    bindingsIndex.addObjCBlockToSeen(usr, block);
+
+    return block;
+  }
 
   ObjCBlock._({
     required String super.usr,
@@ -42,6 +53,17 @@ class ObjCBlock extends BindingType {
       type.toString().replaceAll(_illegalNameChar, '');
   static final _illegalNameChar = RegExp(r'[^0-9a-zA-Z]');
 
+  static String _getBlockUsr(Type returnType, List<Type> argTypes) {
+    // Create a fake USR code for the block. This code is used to dedupe blocks
+    // with the same signature.
+    final usr = StringBuffer();
+    usr.write('objcBlock: ${returnType.cacheKey()}');
+    for (final type in argTypes) {
+      usr.write(' ${type.cacheKey()}');
+    }
+    return usr.toString();
+  }
+
   bool get hasListener => returnType == voidType;
 
   @override

pkgs/ffigen/lib/src/code_generator/objc_built_in_functions.dart

@@ -22,8 +22,16 @@ class ObjCBuiltInFunctions {
   static const newPointerBlock = ObjCImport('newPointerBlock');
   static const newClosureBlock = ObjCImport('newClosureBlock');
   static const getBlockClosure = ObjCImport('getBlockClosure');
+  static const getProtocolMethodSignature =
+      ObjCImport('getProtocolMethodSignature');
+  static const getProtocol = ObjCImport('getProtocol');
   static const objectBase = ObjCImport('ObjCObjectBase');
   static const blockBase = ObjCImport('ObjCBlockBase');
+  static const protocolMethod = ObjCImport('ObjCProtocolMethod');
+  static const protocolListenableMethod =
+      ObjCImport('ObjCProtocolListenableMethod');
+  static const protocolBuilder = ObjCImport('ObjCProtocolBuilder');
+  static const dartProxy = ObjCImport('DartProxy');
 
   // Keep in sync with pkgs/objective_c/ffigen_objc.yaml.
   static const builtInInterfaces = {
@@ -45,12 +53,12 @@ class ObjCBuiltInFunctions {
     'NSMutableArray',
     'NSMutableData',
     'NSMutableDictionary',
+    'NSMutableIndexSet',
     'NSMutableSet',
     'NSMutableString',
     'NSNotification',
     'NSNumber',
     'NSObject',
-    'NSProgress',
     'NSProxy',
     'NSSet',
     'NSString',
@@ -59,9 +67,18 @@ class ObjCBuiltInFunctions {
     'NSValue',
     'Protocol',
   };
+  static const builtInCompounds = {
+    'NSFastEnumerationState',
+    'NSRange',
+  };
 
+  // TODO(https://github.com/dart-lang/native/issues/1173): Ideally this check
+  // would be based on more than just the name.
   bool isBuiltInInterface(String name) =>
       !generateForPackageObjectiveC && builtInInterfaces.contains(name);
+  bool isBuiltInCompound(String name) =>
+      !generateForPackageObjectiveC && builtInCompounds.contains(name);
+  bool isNSObject(String name) => name == 'NSObject';
 
   // We need to load a separate instance of objc_msgSend for each signature. If
   // the return type is a struct, we need to use objc_msgSend_stret instead, and
@@ -96,6 +113,12 @@ class ObjCBuiltInFunctions {
       sel.addDependencies(dependencies);
     }
   }
+
+  static bool isInstanceType(Type type) {
+    if (type is ObjCInstanceType) return true;
+    final baseType = type.typealiasType;
+    return baseType is ObjCNullable && baseType.child is ObjCInstanceType;
+  }
 }
 
 /// A function, global variable, or helper type defined in package:objective_c.