Add NS_ASSUME_NONNULL to all headers and .m @interface declarations

Adds NS_ASSUME_NONNULL_BEGIN/END to every header and .m @interface
declaration that was missing it, improving Swift bridging (nonnull
types bridge as non-optional) and making the nullability contract
explicit for human readers. Some of the wrapped declarations don't
currently contain pointer types, but are included for consistency
and so that future additions to those interfaces will have coverage
by default.

Where adding coverage made existing explicit nonnull annotations
redundant, those are removed. Where a return type or parameter is
genuinely nullable (verified by reading the implementation), an
explicit nullable annotation is added — notably on the dictionary
lookup helpers in ARTNSDictionary+ARTDictionaryUtil.h and parseId
in ARTPresenceMessage+Private.h.

In ARTTypes.h, NS_ASSUME_NONNULL_BEGIN is moved earlier to cover
the *ToStr() C functions that were previously annotated with
inline _Nonnull.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lawrence-forooghian

Source/ARTChannels.m

@@ -6,13 +6,17 @@
 #import "ARTRestChannel.h"
 #import "ARTGCD.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTChannels() {
     __weak id<ARTChannelsDelegate> _delegate; // weak because delegates outlive their counterpart
     dispatch_queue_t _queue;
 }
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTChannels
 
 - (instancetype)initWithDelegate:(id)delegate dispatchQueue:(dispatch_queue_t)queue prefix:(NSString *)prefix {

Source/ARTClientOptions.m

@@ -18,6 +18,8 @@
 
 NSString *ARTDefaultEnvironment = nil;
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTClientOptions ()
 
 @property (nonatomic) NSMutableDictionary<NSString *, id> *pluginData;
@@ -26,6 +28,8 @@ - (instancetype)initDefaults;
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTClientOptions
 
 - (instancetype)initDefaults {

Source/ARTContinuousClock.m

@@ -1,5 +1,7 @@
 #import "ARTContinuousClock.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTContinuousClockInstant ()
 
 - (instancetype)initWithTime:(uint64_t)time NS_DESIGNATED_INITIALIZER;
@@ -13,6 +15,8 @@ - (instancetype)initWithTime:(uint64_t)time NS_DESIGNATED_INITIALIZER;
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTContinuousClock
 
 - (ARTContinuousClockInstant *)now {

Source/ARTCrypto.m

@@ -5,6 +5,8 @@
 
 #define ART_CBC_BLOCK_LENGTH (16)
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTCipherParams ()
 
 - (BOOL)ccAlgorithm:(CCAlgorithm *)algorithm error:(NSError **)error;
@@ -17,6 +19,8 @@ @interface ARTCbcCipher ()
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation NSString (ARTCipherKeyCompatible)
 
 - (NSData *)toData {

Source/ARTEventEmitter.m

@@ -46,12 +46,16 @@ - (NSString *)identification {
 
 #pragma mark - ARTEventListener
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTEventListener ()
 @property (readonly) BOOL invalidated;
 @property (readonly) BOOL timerIsRunning;
 @property (readonly) BOOL hasTimer;
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTEventListener {
     NSNotificationCenter *_center;
     __weak ARTEventEmitter *_eventHandler; // weak because eventEmitter owns self

Source/ARTFallback.m

@@ -10,10 +10,14 @@
     }
 };
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTFallback ()
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTFallback
 
 - (instancetype)initWithFallbackHosts:(nullable NSArray<NSString *> *)fallbackHosts shuffleArray:(void (^)(NSMutableArray *))shuffleArray {

Source/ARTGCD.m

@@ -1,12 +1,16 @@
 #import "ARTGCD.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTScheduledBlockHandle ()
 
 // Mark this as `atomic` to syncronize access to it from `_scheduledBlock` and `cancel`.
 @property (atomic, copy, nullable) dispatch_block_t block;
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTScheduledBlockHandle {
     dispatch_block_t _scheduledBlock;
 }

Source/ARTHttp.m

@@ -3,12 +3,16 @@
 #import "ARTConstants.h"
 #import "ARTInternalLog.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTHttp ()
 
 @property (readonly, nonatomic) id<ARTURLSession> urlSession;
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 Class configuredUrlSessionClass = nil;
 
 #pragma mark - ARTHttp

Source/ARTLocalDevice.m

@@ -40,12 +40,16 @@
     return [ARTAPNSDeviceTokenKey stringByAppendingFormat:@"-%@", tokenType ?: ARTAPNSDeviceDefaultTokenType];
 }
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTLocalDevice ()
 
 @property (nullable, nonatomic, readonly) ARTInternalLog *logger;
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 @implementation ARTLocalDevice
 
 - (instancetype)initWithStorage:(id<ARTDeviceStorage>)storage logger:(nullable ARTInternalLog *)logger {

Source/ARTRealtime.m

@@ -57,12 +57,16 @@
 #import "ARTWrapperSDKProxyRealtime+Private.h"
 #import "ARTConnectionDetails+Private.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface ARTConnectionStateChange ()
 
 - (void)setRetryIn:(NSTimeInterval)retryIn;
 
 @end
 
+NS_ASSUME_NONNULL_END
+
 #pragma mark - ARTRealtime implementation
 
 @implementation ARTRealtime {