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Selector Signal Interoperability. #33

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afd00ec
Selector Signal Interoperability.
andersio Nov 12, 2016
39bf8b9
Improved KVO-involving test cases.
andersio Nov 13, 2016
9ae4776
Brought `respondsToSelector` swizzling into line with others.
andersio Nov 13, 2016
1901739
Fixed a few KVO interoperability issues.
andersio Nov 13, 2016
d983255
Added stress tests for the new `signalForSelector:` impl.
andersio Nov 13, 2016
fe1bdb6
Documented the `forwardInvocation:` swizzling.
andersio Nov 13, 2016
632ecad
Guard against a potential infinite feedback loop.
andersio Nov 13, 2016
84aa0a4
Update podspec CI test config.
andersio Nov 13, 2016
71594bf
Merge branch 'master' into selector-signal-interop
andersio Nov 18, 2016
a98c30c
Ported a few changes from the Swift implementation.
andersio Nov 19, 2016
4dac92c
Merge branch 'master' into selector-signal-interop
andersio Nov 19, 2016
83f16d5
Fixed a thread safety issue in the method interception logic.
andersio Nov 19, 2016
04c5f76
Revert "Fixed a thread safety issue in the method interception logic."
andersio Nov 20, 2016
96bd2b7
Explicit locking for the interop-implementation table.
andersio Nov 20, 2016
306a0da
Abolished the interop-implementation table.
andersio Nov 20, 2016
7dfc280
Marked a return value for an assertion with `__attribute__((unused))`.
andersio Nov 20, 2016
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8 changes: 8 additions & 0 deletions ReactiveObjC.xcodeproj/project.pbxproj
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,9 @@
7DFBED6C1CDB8DE300EE435B /* RACTestUIButton.m in Sources */ = {isa = PBXBuildFile; fileRef = D0C3131D19EF2D9700984962 /* RACTestUIButton.m */; };
7DFBED6E1CDB918900EE435B /* UIBarButtonItem+RACCommandSupport.m in Sources */ = {isa = PBXBuildFile; fileRef = D03764C719EDA41200A782A9 /* UIBarButtonItem+RACCommandSupport.m */; };
7DFBED6F1CDB926400EE435B /* UIBarButtonItem+RACCommandSupport.h in Headers */ = {isa = PBXBuildFile; fileRef = D03764C619EDA41200A782A9 /* UIBarButtonItem+RACCommandSupport.h */; settings = {ATTRIBUTES = (Public, ); }; };
9AE2F1121DD8BF96008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9AE2F10E1DD8B827008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m */; };
9AE2F1131DD8BF97008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9AE2F10E1DD8B827008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m */; };
9AE2F1141DD8BF98008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9AE2F10E1DD8B827008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m */; };
A1046B7A1BFF5661004D8045 /* EXTRuntimeExtensions.h in Headers */ = {isa = PBXBuildFile; fileRef = D037666719EDA57100A782A9 /* EXTRuntimeExtensions.h */; settings = {ATTRIBUTES = (Private, ); }; };
A1046B7B1BFF5662004D8045 /* EXTRuntimeExtensions.h in Headers */ = {isa = PBXBuildFile; fileRef = D037666719EDA57100A782A9 /* EXTRuntimeExtensions.h */; settings = {ATTRIBUTES = (Private, ); }; };
A1046B7C1BFF5662004D8045 /* EXTRuntimeExtensions.h in Headers */ = {isa = PBXBuildFile; fileRef = D037666719EDA57100A782A9 /* EXTRuntimeExtensions.h */; settings = {ATTRIBUTES = (Private, ); }; };
Expand Down Expand Up @@ -769,6 +772,7 @@
7A70657E1A3F88B8001E8354 /* RACKVOProxy.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RACKVOProxy.m; sourceTree = "<group>"; };
7A7065831A3F8967001E8354 /* RACKVOProxySpec.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RACKVOProxySpec.m; sourceTree = "<group>"; };
7DFBED031CDB8C9500EE435B /* ReactiveObjCTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = ReactiveObjCTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
9AE2F10E1DD8B827008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NSObjectRACSelectorSignalPerformanceTests.m; sourceTree = "<group>"; };
A97451331B3A935E00F48E55 /* watchOS-Application.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = "watchOS-Application.xcconfig"; sourceTree = "<group>"; };
A97451341B3A935E00F48E55 /* watchOS-Base.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = "watchOS-Base.xcconfig"; sourceTree = "<group>"; };
A97451351B3A935E00F48E55 /* watchOS-Framework.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = "watchOS-Framework.xcconfig"; sourceTree = "<group>"; };
Expand Down Expand Up @@ -1396,6 +1400,7 @@
D037667E19EDA60000A782A9 /* NSObjectRACPropertySubscribingExamples.m */,
D037667F19EDA60000A782A9 /* NSObjectRACPropertySubscribingSpec.m */,
D037668019EDA60000A782A9 /* NSObjectRACSelectorSignalSpec.m */,
9AE2F10E1DD8B827008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m */,
D037668119EDA60000A782A9 /* NSStringRACKeyPathUtilitiesSpec.m */,
D037668319EDA60000A782A9 /* NSURLConnectionRACSupportSpec.m */,
D037668419EDA60000A782A9 /* NSUserDefaultsRACSupportSpec.m */,
Expand Down Expand Up @@ -2132,6 +2137,7 @@
isa = PBXSourcesBuildPhase;
buildActionMask = 2147483647;
files = (
9AE2F1141DD8BF98008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m in Sources */,
7DFBED321CDB8DE300EE435B /* NSEnumeratorRACSequenceAdditionsSpec.m in Sources */,
7DFBED331CDB8DE300EE435B /* NSNotificationCenterRACSupportSpec.m in Sources */,
7DFBED351CDB8DE300EE435B /* NSObjectRACDeallocatingSpec.m in Sources */,
Expand Down Expand Up @@ -2339,6 +2345,7 @@
isa = PBXSourcesBuildPhase;
buildActionMask = 2147483647;
files = (
9AE2F1121DD8BF96008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m in Sources */,
D03766C719EDA60000A782A9 /* NSObjectRACPropertySubscribingExamples.m in Sources */,
D03766E319EDA60000A782A9 /* RACDelegateProxySpec.m in Sources */,
D03766F919EDA60000A782A9 /* RACSerialDisposableSpec.m in Sources */,
Expand Down Expand Up @@ -2510,6 +2517,7 @@
D03766C619EDA60000A782A9 /* NSObjectRACLiftingSpec.m in Sources */,
D0C3131F19EF2D9700984962 /* RACTestExampleScheduler.m in Sources */,
D03766D219EDA60000A782A9 /* NSURLConnectionRACSupportSpec.m in Sources */,
9AE2F1131DD8BF97008A8FDD /* NSObjectRACSelectorSignalPerformanceTests.m in Sources */,
D03766F419EDA60000A782A9 /* RACSequenceAdditionsSpec.m in Sources */,
D03766EE19EDA60000A782A9 /* RACMulticastConnectionSpec.m in Sources */,
D03766EA19EDA60000A782A9 /* RACKVOChannelSpec.m in Sources */,
Expand Down
185 changes: 129 additions & 56 deletions ReactiveObjC/NSObject+RACSelectorSignal.m
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Original file line number Diff line number Diff line change
Expand Up @@ -15,15 +15,22 @@
#import "RACSubject.h"
#import "RACTuple.h"
#import "NSObject+RACDescription.h"
#import "EXTScope.h"
#import <objc/message.h>
#import <objc/runtime.h>
#import "pthread.h"

NSString * const RACSelectorSignalErrorDomain = @"RACSelectorSignalErrorDomain";
const NSInteger RACSelectorSignalErrorMethodSwizzlingRace = 1;

static NSString * const RACSignalForSelectorAliasPrefix = @"rac_alias_";
static NSString * const RACSubclassSuffix = @"_RACSelectorSignal";
static const char * RACSignalForSelectorAliasPrefix = "rac_alias_";
static const int RACSignalForSelectorAliasPrefixLength = 10;
static const char * RACSignalForSelectorInteropAliasPrefix = "rac_interop_";
static const int RACSignalForSelectorInteropAliasPrefixLength = 12;
static void *RACSubclassAssociationKey = &RACSubclassAssociationKey;
static void *RACInteropImplsKey = &RACInteropImplsKey;
static void *RACInteropImplsLockKey = &RACInteropImplsLockKey;

static NSMutableSet *swizzledClasses() {
static NSMutableSet *set;
Expand All @@ -38,32 +45,10 @@

@implementation NSObject (RACSelectorSignal)

static BOOL RACForwardInvocation(id self, NSInvocation *invocation) {
SEL aliasSelector = RACAliasForSelector(invocation.selector);
RACSubject *subject = objc_getAssociatedObject(self, aliasSelector);
static void RACSwizzleForwardInvocation(Class baseClass) {
Class statedClass = class_getSuperclass(baseClass);

Class class = object_getClass(invocation.target);
BOOL respondsToAlias = [class instancesRespondToSelector:aliasSelector];
if (respondsToAlias) {
invocation.selector = aliasSelector;
[invocation invoke];
}

if (subject == nil) return respondsToAlias;

[subject sendNext:invocation.rac_argumentsTuple];
return YES;
}

static void RACSwizzleForwardInvocation(Class class) {
SEL forwardInvocationSEL = @selector(forwardInvocation:);
Method forwardInvocationMethod = class_getInstanceMethod(class, forwardInvocationSEL);

// Preserve any existing implementation of -forwardInvocation:.
void (*originalForwardInvocation)(id, SEL, NSInvocation *) = NULL;
if (forwardInvocationMethod != NULL) {
originalForwardInvocation = (__typeof__(originalForwardInvocation))method_getImplementation(forwardInvocationMethod);
}

// Set up a new version of -forwardInvocation:.
//
Expand All @@ -75,26 +60,83 @@ static void RACSwizzleForwardInvocation(Class class) {
// was no existing implementation, throw an unrecognized selector
// exception.
id newForwardInvocation = ^(id self, NSInvocation *invocation) {
BOOL matched = RACForwardInvocation(self, invocation);
if (matched) return;
SEL originalSelector = invocation.selector;
SEL aliasSelector = RACAliasForSelector(originalSelector);
SEL interopAliasSelector = RACInteropAliasForSelector(originalSelector);

if (originalForwardInvocation == NULL) {
[self doesNotRecognizeSelector:invocation.selector];
} else {
originalForwardInvocation(self, forwardInvocationSEL, invocation);
RACSubject* subject = objc_getAssociatedObject(self, aliasSelector);

@onExit {
if (subject != nil) {
[subject sendNext:invocation.rac_argumentsTuple];
}
};

// RAC exchanges implementations at runtime so as to invoke the desired
// version without using fragile dependencies like libffi. This means
// all instances that had been applied `signalForSelector:` are
// non-threadsafe as any mutable instances.

Method method = class_getInstanceMethod(statedClass, originalSelector);
const char* typeEncoding = method_getTypeEncoding(method);

if (class_respondsToSelector(baseClass, interopAliasSelector)) {
// `self` uses a runtime subclass generated by third-party APIs, and RAC
// found an existing implementation for the selector at the setup time.
// Call that implementation if it is not the ObjC message forwarder.
IMP interopImpl = class_getMethodImplementation(baseClass, interopAliasSelector);
IMP oldImpl = class_replaceMethod(baseClass, originalSelector, interopImpl, typeEncoding);
invocation.selector = originalSelector;
[invocation invoke];
class_replaceMethod(baseClass, originalSelector, oldImpl, typeEncoding);
return;
}

BOOL forwardRegardless = NO;

if (method != nil) {
IMP statedClassImpl = method_getImplementation(method);

if (statedClassImpl != _objc_msgForward) {
// The stated class has an implementation of the selector. Call that
// implementation if it is not the ObjC message forwarder.
Method aliasMethod = rac_getImmediateInstanceMethod(baseClass, aliasSelector);

if (statedClassImpl != method_getImplementation(aliasMethod)) {
class_replaceMethod(baseClass, aliasSelector, statedClassImpl, typeEncoding);
}

invocation.selector = aliasSelector;
[invocation invoke];

return;
}

forwardRegardless = YES;
}

// No appropriate implementation was found. Forward the invocation to the
// stated class' `forwardInvocation:` only if the selector had not been
// intercepted via `signalForSelector:`.
//
// `subject` is usually null except for optional protocol requirements
// that are implemented at runtime through RAC.
if (subject == nil || forwardRegardless) {
// Forward the invocation to the closest `forwardInvocation:` in the
// inheritance hierarchy.
Method forwardInvocationMethod = class_getInstanceMethod(statedClass, forwardInvocationSEL);
void*(*superForwardInvocation)(id, SEL, NSInvocation*) = (__typeof__(superForwardInvocation)) method_getImplementation(forwardInvocationMethod);
superForwardInvocation(self, forwardInvocationSEL, invocation);
}
};

class_replaceMethod(class, forwardInvocationSEL, imp_implementationWithBlock(newForwardInvocation), "v@:@");
class_replaceMethod(baseClass, forwardInvocationSEL, imp_implementationWithBlock(newForwardInvocation), "v@:@");
}

static void RACSwizzleRespondsToSelector(Class class) {
static void RACSwizzleRespondsToSelector(Class baseClass) {
Class statedClass = class_getSuperclass(baseClass);
SEL respondsToSelectorSEL = @selector(respondsToSelector:);

// Preserve existing implementation of -respondsToSelector:.
Method respondsToSelectorMethod = class_getInstanceMethod(class, respondsToSelectorSEL);
BOOL (*originalRespondsToSelector)(id, SEL, SEL) = (__typeof__(originalRespondsToSelector))method_getImplementation(respondsToSelectorMethod);

// Set up a new version of -respondsToSelector: that returns YES for methods
// added by -rac_signalForSelector:.
//
Expand All @@ -103,17 +145,19 @@ static void RACSwizzleRespondsToSelector(Class class) {
// the instance has a signal for the selector.
// Otherwise, call the original -respondsToSelector:.
id newRespondsToSelector = ^ BOOL (id self, SEL selector) {
Method method = rac_getImmediateInstanceMethod(class, selector);
Method method = rac_getImmediateInstanceMethod(baseClass, selector);

if (method != NULL && method_getImplementation(method) == _objc_msgForward) {
SEL aliasSelector = RACAliasForSelector(selector);
if (objc_getAssociatedObject(self, aliasSelector) != nil) return YES;
}

return originalRespondsToSelector(self, respondsToSelectorSEL, selector);
Method superMethod = class_getInstanceMethod(statedClass, respondsToSelectorSEL);
BOOL(*superRespondsToSelector)(id, SEL, SEL) = (__typeof__(superRespondsToSelector)) method_getImplementation(superMethod);
return superRespondsToSelector(self, respondsToSelectorSEL, selector);
};

class_replaceMethod(class, respondsToSelectorSEL, imp_implementationWithBlock(newRespondsToSelector), method_getTypeEncoding(respondsToSelectorMethod));
class_replaceMethod(baseClass, respondsToSelectorSEL, imp_implementationWithBlock(newRespondsToSelector), "v@::");
}

static void RACSwizzleGetClass(Class class, Class statedClass) {
Expand All @@ -125,32 +169,30 @@ static void RACSwizzleGetClass(Class class, Class statedClass) {
class_replaceMethod(class, selector, newIMP, method_getTypeEncoding(method));
}

static void RACSwizzleMethodSignatureForSelector(Class class) {
static void RACSwizzleMethodSignatureForSelector(Class baseClass) {
Class statedClass = class_getSuperclass(baseClass);
SEL methodSignatureForSelectorSEL = @selector(methodSignatureForSelector:);

IMP newIMP = imp_implementationWithBlock(^(id self, SEL selector) {
// Don't send the -class message to the receiver because we've changed
// that to return the original class.
Class actualClass = object_getClass(self);
Method method = class_getInstanceMethod(actualClass, selector);
Method method = class_getInstanceMethod(baseClass, selector);

if (method == NULL) {
// Messages that the original class dynamically implements fall
// here.
//
// Call the original class' -methodSignatureForSelector:.
struct objc_super target = {
.super_class = class_getSuperclass(class),
.receiver = self,
};
NSMethodSignature * (*messageSend)(struct objc_super *, SEL, SEL) = (__typeof__(messageSend))objc_msgSendSuper;
return messageSend(&target, @selector(methodSignatureForSelector:), selector);
Method superMethod = class_getInstanceMethod(statedClass, methodSignatureForSelectorSEL);
NSMethodSignature * (*messageSend)(id, SEL, SEL) = (__typeof__(messageSend)) method_getImplementation(superMethod);
return messageSend(self, methodSignatureForSelectorSEL, selector);
}

char const *encoding = method_getTypeEncoding(method);
return [NSMethodSignature signatureWithObjCTypes:encoding];
});

SEL selector = @selector(methodSignatureForSelector:);
Method methodSignatureForSelectorMethod = class_getInstanceMethod(class, selector);
class_replaceMethod(class, selector, newIMP, method_getTypeEncoding(methodSignatureForSelectorMethod));
class_replaceMethod(baseClass, methodSignatureForSelectorSEL, newIMP, "@@::");
}

// It's hard to tell which struct return types use _objc_msgForward, and
Expand All @@ -173,6 +215,7 @@ static void RACCheckTypeEncoding(const char *typeEncoding) {

static RACSignal *NSObjectRACSignalForSelector(NSObject *self, SEL selector, Protocol *protocol) {
SEL aliasSelector = RACAliasForSelector(selector);
SEL interopAliasSelector = RACInteropAliasForSelector(selector);

@synchronized (self) {
RACSubject *subject = objc_getAssociatedObject(self, aliasSelector);
Expand Down Expand Up @@ -224,8 +267,18 @@ static void RACCheckTypeEncoding(const char *typeEncoding) {

RACCheckTypeEncoding(typeEncoding);

BOOL addedAlias __attribute__((unused)) = class_addMethod(class, aliasSelector, method_getImplementation(targetMethod), typeEncoding);
NSCAssert(addedAlias, @"Original implementation for %@ is already copied to %@ on %@", NSStringFromSelector(selector), NSStringFromSelector(aliasSelector), class);
@synchronized (class) {
if (!class_respondsToSelector(class, interopAliasSelector)) {
Method dynamicImmediateMethod = rac_getImmediateInstanceMethod(class, selector);
if (dynamicImmediateMethod) {
IMP dynamicImmediateImpl = method_getImplementation(dynamicImmediateMethod);
if (dynamicImmediateImpl != _objc_msgForward) {
BOOL success __attribute__((unused)) = class_addMethod(class, interopAliasSelector, dynamicImmediateImpl, typeEncoding);
NSCAssert(success, @"Unexpected race condition: `%@` has already been added, and subsequent attempts should have been ignored.", NSStringFromSelector(interopAliasSelector));
}
}
}
}

// Redefine the selector to call -forwardInvocation:.
class_replaceMethod(class, selector, _objc_msgForward, method_getTypeEncoding(targetMethod));
Expand All @@ -236,8 +289,28 @@ static void RACCheckTypeEncoding(const char *typeEncoding) {
}

static SEL RACAliasForSelector(SEL originalSelector) {
NSString *selectorName = NSStringFromSelector(originalSelector);
return NSSelectorFromString([RACSignalForSelectorAliasPrefix stringByAppendingString:selectorName]);
return _RACAliasForSelector(originalSelector, RACSignalForSelectorAliasPrefix, RACSignalForSelectorAliasPrefixLength);
}

static SEL RACInteropAliasForSelector(SEL originalSelector) {
return _RACAliasForSelector(originalSelector, RACSignalForSelectorInteropAliasPrefix, RACSignalForSelectorInteropAliasPrefixLength);
}

static SEL _RACAliasForSelector(SEL originalSelector, const char* prefix, int prefixLength) {
const char* selectorString = sel_getName(originalSelector);
unsigned long length = strlen(selectorString);
unsigned long finalLength = length + prefixLength;

char* buffer = malloc(finalLength + 1);
@onExit {
free(buffer);
};

memcpy(buffer, prefix, prefixLength);
memcpy(buffer + prefixLength, selectorString, length);
*(buffer + finalLength) = '\0';

return sel_registerName(buffer);
}

static const char *RACSignatureForUndefinedSelector(SEL selector) {
Expand Down
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