Enable CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION for the projects.

objectivec/GPBMessage.h

@@ -127,7 +127,7 @@ CF_EXTERN_C_END
 
 // Same as -[data], except a delimiter is added to the start of the data
 // indicating the size of the message data that follows.
-- (nullable NSData *)delimitedData;
+- (NSData *)delimitedData;
 
 // Returns the size of the object if it were serialized.
 // This is not a cached value. If you are following a pattern like this:

objectivec/GPBMessage.m

@@ -1212,7 +1212,8 @@ static GPBUnknownFieldSet *GetOrMakeUnknownFields(GPBMessage *self) {
     NSLog(@"%@: Internal exception while building message delimitedData: %@",
           [self class], exception);
 #endif
-    data = nil;
+    // If it happens, truncate.
+    data.length = 0;
   }
   [stream release];
   return data;
@@ -1791,7 +1792,12 @@ static GPBUnknownFieldSet *GetOrMakeUnknownFields(GPBMessage *self) {
     extensionMap_ = [[NSMutableDictionary alloc] init];
   }
 
-  [extensionMap_ setObject:value forKey:extension];
+  // This pointless cast is for CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION.
+  // Without it, the compiler complains we're passing an id nullable when
+  // setObject:forKey: requires a id nonnull for the value. The check for
+  // !value at the start of the method ensures it isn't nil, but the check
+  // isn't smart enough to realize that.
+  [extensionMap_ setObject:(id)value forKey:extension];
 
   GPBExtensionDescriptor *descriptor = extension;
 

objectivec/GPBUtilities.h

@@ -44,7 +44,7 @@ NS_ASSUME_NONNULL_BEGIN
 // most likely won't exactly match the original .proto file.
 NSString *GPBTextFormatForMessage(GPBMessage *message,
                                   NSString * __nullable lineIndent);
-NSString *GPBTextFormatForUnknownFieldSet(GPBUnknownFieldSet *unknownSet,
+NSString *GPBTextFormatForUnknownFieldSet(GPBUnknownFieldSet * __nullable unknownSet,
                                           NSString * __nullable lineIndent);
 
 //

objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj

@@ -787,6 +787,7 @@
 				CLANG_ANALYZER_SECURITY_INSECUREAPI_STRCPY = YES;
 				CLANG_STATIC_ANALYZER_MODE = deep;
 				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION = YES;
 				CLANG_WARN_OBJC_IMPLICIT_ATOMIC_PROPERTIES = YES;
 				CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS = YES;
 				CLANG_WARN_SUSPICIOUS_IMPLICIT_CONVERSION = YES;
@@ -831,6 +832,7 @@
 				CLANG_ANALYZER_SECURITY_INSECUREAPI_STRCPY = YES;
 				CLANG_STATIC_ANALYZER_MODE = deep;
 				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION = YES;
 				CLANG_WARN_OBJC_IMPLICIT_ATOMIC_PROPERTIES = YES;
 				CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS = YES;
 				CLANG_WARN_SUSPICIOUS_IMPLICIT_CONVERSION = YES;

objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj

@@ -949,6 +949,7 @@
 				CLANG_ANALYZER_SECURITY_INSECUREAPI_STRCPY = YES;
 				CLANG_STATIC_ANALYZER_MODE = deep;
 				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION = YES;
 				CLANG_WARN_OBJC_IMPLICIT_ATOMIC_PROPERTIES = YES;
 				CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS = YES;
 				CLANG_WARN_SUSPICIOUS_IMPLICIT_CONVERSION = YES;
@@ -994,6 +995,7 @@
 				CLANG_ANALYZER_SECURITY_INSECUREAPI_STRCPY = YES;
 				CLANG_STATIC_ANALYZER_MODE = deep;
 				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION = YES;
 				CLANG_WARN_OBJC_IMPLICIT_ATOMIC_PROPERTIES = YES;
 				CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS = YES;
 				CLANG_WARN_SUSPICIOUS_IMPLICIT_CONVERSION = YES;

objectivec/Tests/GPBCodedInputStreamTests.m

@@ -225,8 +225,10 @@
   // Serialize and parse it.  Make sure to parse from an InputStream, not
   // directly from a ByteString, so that CodedInputStream uses buffered
   // reading.
+  NSData *messageData = message.data;
+  XCTAssertNotNil(messageData);
   GPBCodedInputStream* stream =
-      [GPBCodedInputStream streamWithData:message.data];
+      [GPBCodedInputStream streamWithData:messageData];
   TestAllTypes* message2 = [TestAllTypes parseFromCodedInputStream:stream
                                                  extensionRegistry:nil
                                                              error:NULL];

objectivec/Tests/GPBMessageTests.m

@@ -195,7 +195,9 @@
 
   // Test merging from data.
   result = [self mergeExtensionsDestination];
-  [result mergeFromData:[[self mergeExtensionsSource] data]
+  NSData *data = [[self mergeExtensionsSource] data];
+  XCTAssertNotNil(data);
+  [result mergeFromData:data
       extensionRegistry:[UnittestRoot extensionRegistry]];
   resultData = [result data];
   XCTAssertEqualObjects(resultData, mergeResultData);
@@ -1884,7 +1886,9 @@
   XCTAssertEqual(msg.bar, EnumTestMsg_MyEnum_One);
   XCTAssertEqual(msg.baz, EnumTestMsg_MyEnum_NegOne);
   // Bounce to wire and back.
-  EnumTestMsg *msgPrime = [EnumTestMsg parseFromData:[msg data] error:NULL];
+  NSData *data = [msg data];
+  XCTAssertNotNil(data);
+  EnumTestMsg *msgPrime = [EnumTestMsg parseFromData:data error:NULL];
   XCTAssertEqualObjects(msgPrime, msg);
   XCTAssertEqual(msgPrime.foo, EnumTestMsg_MyEnum_Zero);
   XCTAssertEqual(msgPrime.bar, EnumTestMsg_MyEnum_One);
@@ -1896,7 +1900,9 @@
   XCTAssertEqual(msg.bar, EnumTestMsg_MyEnum_Two);
   XCTAssertEqual(msg.baz, EnumTestMsg_MyEnum_NegTwo);
   // Bounce to wire and back.
-  msgPrime = [EnumTestMsg parseFromData:[msg data] error:NULL];
+  data = [msg data];
+  XCTAssertNotNil(data);
+  msgPrime = [EnumTestMsg parseFromData:data error:NULL];
   XCTAssertEqualObjects(msgPrime, msg);
   XCTAssertEqual(msgPrime.foo, EnumTestMsg_MyEnum_Zero);
   XCTAssertEqual(msgPrime.bar, EnumTestMsg_MyEnum_Two);
@@ -1917,7 +1923,9 @@
   XCTAssertEqual([msg.mumbleArray valueAtIndex:3], EnumTestMsg_MyEnum_NegOne);
   XCTAssertEqual([msg.mumbleArray valueAtIndex:4], EnumTestMsg_MyEnum_NegTwo);
   // Bounce to wire and back.
-  msgPrime = [EnumTestMsg parseFromData:[msg data] error:NULL];
+  data = [msg data];
+  XCTAssertNotNil(data);
+  msgPrime = [EnumTestMsg parseFromData:data error:NULL];
   XCTAssertEqualObjects(msgPrime, msg);
   XCTAssertEqual([msgPrime.mumbleArray valueAtIndex:0],
                  EnumTestMsg_MyEnum_Zero);