[pigeon] Added the ability for objc to return errors. (#113)

Author: gaaclarke

packages/pigeon/example/README.md

@@ -42,7 +42,7 @@ flutter pub run pigeon \
 @end
 
 @implementation MyApi
--(SearchReply*)search:(SearchRequest*)request {
+-(SearchReply*)search:(SearchRequest*)request error:(FlutterError **)error {
   SearchReply *reply = [[SearchReply alloc] init];
   reply.result =
       [NSString stringWithFormat:@"Hi %@!", request.query];

packages/pigeon/lib/dart_generator.dart

@@ -22,8 +22,18 @@ void _writeHostApi(Indent indent, Api api) {
             'BasicMessageChannel(\'$channelName\', StandardMessageCodec());');
         indent.dec();
         indent.dec();
-        indent.writeln('Map replyMap = await channel.send(requestMap);');
-        indent.writeln('return ${func.returnType}._fromMap(replyMap);');
+        indent.writeln('');
+        indent.format('''Map replyMap = await channel.send(requestMap);
+if (replyMap['error'] != null) {
+\tMap error = replyMap['${Keys.error}'];
+\tthrow PlatformException(
+\t\t\tcode: error['${Keys.errorCode}'],
+\t\t\tmessage: error['${Keys.errorMessage}'],
+\t\t\tdetails: error['${Keys.errorDetails}']);
+} else {
+\treturn ${func.returnType}._fromMap(replyMap[\'${Keys.result}\']);
+}
+''');
       });
     }
   });

packages/pigeon/lib/generator_tools.dart

@@ -31,6 +31,9 @@ class Indent {
   /// String used for newlines (ex "\n").
   final String newline = '\n';
 
+  /// String used to represent a tab.
+  final String tab = '  ';
+
   /// Increase the indentation level.
   void inc() {
     _count += 1;
@@ -45,11 +48,18 @@ class Indent {
   String str() {
     String result = '';
     for (int i = 0; i < _count; i++) {
-      result += '  ';
+      result += tab;
     }
     return result;
   }
 
+  /// Replaces the newlines and tabs of input and adds it to the stream.
+  void format(String input) {
+    for (String line in input.split('\n')) {
+      writeln(line.replaceAll('\t', tab));
+    }
+  }
+
   /// Scoped increase of the ident level.  For the execution of [func] the
   /// indentation will be incremented.
   void scoped(String begin, String end, Function func) {
@@ -126,3 +136,21 @@ const String generatedCodeWarning =
 
 /// String to be printed after `generatedCodeWarning`.
 const String seeAlsoWarning = 'See also: https://pub.dev/packages/pigeon';
+
+/// Collection of keys used in dictionaries across generators.
+class Keys {
+  /// The key in the result hash for the 'result' value.
+  static const String result = 'result';
+
+  /// The key in the result hash for the 'error' value.
+  static const String error = 'error';
+
+  /// The key in an error hash for the 'code' value.
+  static const String errorCode = 'code';
+
+  /// The key in an error hash for the 'message' value.
+  static const String errorMessage = 'message';
+
+  /// The key in an error hash for the 'details' value.
+  static const String errorDetails = 'details';
+}

packages/pigeon/lib/java_generator.dart

@@ -62,8 +62,21 @@ void _writeHostApi(Indent indent, Api api) {
               final String returnType = method.returnType;
               indent.writeln(
                   '$argType input = $argType.fromMap((HashMap)message);');
-              indent.writeln('$returnType output = api.${method.name}(input);');
-              indent.writeln('reply.reply(output.toMap());');
+              indent.writeln(
+                  'HashMap<String, HashMap> wrapped = new HashMap<String, HashMap>();');
+              indent.write('try ');
+              indent.scoped('{', '}', () {
+                indent
+                    .writeln('$returnType output = api.${method.name}(input);');
+                indent
+                    .writeln('wrapped.put("${Keys.result}", output.toMap());');
+              });
+              indent.write('catch (Exception exception) ');
+              indent.scoped('{', '}', () {
+                indent.writeln(
+                    'wrapped.put("${Keys.error}", wrapError(exception));');
+              });
+              indent.writeln('reply.reply(wrapped);');
             });
           });
         });
@@ -200,5 +213,13 @@ void generateJava(JavaOptions options, Root root, StringSink sink) {
         _writeFlutterApi(indent, api);
       }
     }
+
+    indent.format('''private static HashMap wrapError(Exception exception) {
+\tHashMap<String, Object> errorMap = new HashMap<String, Object>();
+\terrorMap.put("${Keys.errorMessage}", exception.toString());
+\terrorMap.put("${Keys.errorCode}", null);
+\terrorMap.put("${Keys.errorDetails}", null);
+\treturn errorMap;
+}''');
   });
 }

packages/pigeon/lib/objc_generator.dart

@@ -69,6 +69,7 @@ void generateObjcHeader(ObjcOptions options, Root root, StringSink sink) {
   indent.writeln('// $seeAlsoWarning');
   indent.writeln('#import <Foundation/Foundation.h>');
   indent.writeln('@protocol FlutterBinaryMessenger;');
+  indent.writeln('@class FlutterError;');
   indent.writeln('@class FlutterStandardTypedData;');
   indent.writeln('');
 
@@ -104,7 +105,8 @@ void generateObjcHeader(ObjcOptions options, Root root, StringSink sink) {
       for (Method func in api.methods) {
         final String returnType = _className(options.prefix, func.returnType);
         final String argType = _className(options.prefix, func.argType);
-        indent.writeln('-($returnType *)${func.name}:($argType*)input;');
+        indent.writeln(
+            '-($returnType *)${func.name}:($argType*)input error:(FlutterError **)error;');
       }
       indent.writeln('@end');
       indent.writeln('');
@@ -175,8 +177,10 @@ void _writeHostApiSource(Indent indent, ObjcOptions options, Api api) {
             final String returnType =
                 _className(options.prefix, func.returnType);
             indent.writeln('$argType *input = [$argType fromMap:message];');
-            indent.writeln('$returnType *output = [api ${func.name}:input];');
-            indent.writeln('callback([output toMap]);');
+            indent.writeln('FlutterError *error;');
+            indent.writeln(
+                '$returnType *output = [api ${func.name}:input error:&error];');
+            indent.writeln('callback(wrapResult([output toMap], error));');
           });
         });
         indent.write('else ');
@@ -247,6 +251,28 @@ void generateObjcSource(ObjcOptions options, Root root, StringSink sink) {
   indent.writeln('#import <Flutter/Flutter.h>');
   indent.writeln('');
 
+  indent.writeln('#if !__has_feature(objc_arc)');
+  indent.writeln('#error File requires ARC to be enabled.');
+  indent.writeln('#endif');
+  indent.addln('');
+
+  indent.format(
+      '''static NSDictionary* wrapResult(NSDictionary *result, FlutterError *error) {
+\tNSDictionary *errorDict = (NSDictionary *)[NSNull null];
+\tif (error) {
+\t\terrorDict = [NSDictionary dictionaryWithObjectsAndKeys:
+\t\t\t\t(error.code ? error.code : [NSNull null]), @"${Keys.errorCode}",
+\t\t\t\t(error.message ? error.message : [NSNull null]), @"${Keys.errorMessage}",
+\t\t\t\t(error.details ? error.details : [NSNull null]), @"${Keys.errorDetails}",
+\t\t\t\tnil];
+\t}
+\treturn [NSDictionary dictionaryWithObjectsAndKeys:
+\t\t\t(result ? result : [NSNull null]), @"${Keys.result}",
+\t\t\terrorDict, @"${Keys.error}",
+\t\t\tnil];
+}''');
+  indent.addln('');
+
   for (Class klass in root.classes) {
     final String className = _className(options.prefix, klass.name);
     indent.writeln('@interface $className ()');

packages/pigeon/run_tests.sh

@@ -19,6 +19,7 @@ test_pigeon_ios() {
     -isysroot $(xcrun --sdk iphoneos --show-sdk-path) \
     -F $framework_path \
     -Werror \
+    -fobjc-arc \
     -c $temp_dir/pigeon.m \
     -o $temp_dir/pigeon.o
 

packages/pigeon/test/objc_generator_test.dart

@@ -52,7 +52,7 @@ void main() {
     expect(code, contains('@interface Input'));
     expect(code, contains('@interface Output'));
     expect(code, contains('@protocol Api'));
-    expect(code, matches('Output.*doSomething.*Input'));
+    expect(code, matches('Output.*doSomething.*Input.*FlutterError'));
     expect(code, contains('ApiSetup('));
   });