Stop assuming all unknown attributes have the C quality in MTRDevice.

src/darwin/Framework/CHIP/MTRCluster.h

@@ -132,6 +132,17 @@ MTR_AVAILABLE(ios(16.1), macos(13.0), watchos(9.1), tvos(16.1))
  */
 @property (nonatomic, copy, nullable) NSNumber * minEventNumber MTR_AVAILABLE(ios(16.4), macos(13.3), watchos(9.4), tvos(16.4));
 
+/**
+ * Controls whether attributes without known schema (e.g. vendor-specific
+ * attributes) should be assumed to be reportable normally via subscriptions.
+ * The default is YES.
+ *
+ * This setting is only relevant to some consumers of MTRReadParams.  One of
+ * those consumers is readAttributeWithEndpointID:clusterID:attributeID:params:
+ * on MTRDevice.
+ */
+@property (nonatomic, assign, getter=shouldAssumeUnknownAttributesReportable) BOOL assumeUnknownAttributesReportable MTR_NEWLY_AVAILABLE;
+
 @end
 
 /**

src/darwin/Framework/CHIP/MTRCluster.mm

@@ -84,6 +84,7 @@ - (instancetype)init
 {
     if (self = [super init]) {
         _filterByFabric = YES;
+        _assumeUnknownAttributesReportable = YES;
     }
     return self;
 }
@@ -93,6 +94,7 @@ - (id)copyWithZone:(NSZone * _Nullable)zone
     auto other = [[MTRReadParams alloc] init];
     other.filterByFabric = self.filterByFabric;
     other.minEventNumber = self.minEventNumber;
+    other.assumeUnknownAttributesReportable = self.assumeUnknownAttributesReportable;
     return other;
 }
 
@@ -124,6 +126,7 @@ - (id)copyWithZone:(NSZone * _Nullable)zone
     auto other = [[MTRSubscribeParams alloc] initWithMinInterval:self.minInterval maxInterval:self.maxInterval];
     other.filterByFabric = self.filterByFabric;
     other.minEventNumber = self.minEventNumber;
+    other.assumeUnknownAttributesReportable = self.assumeUnknownAttributesReportable;
     other.replaceExistingSubscriptions = self.replaceExistingSubscriptions;
     other.reportEventsUrgently = self.reportEventsUrgently;
     other.resubscribeAutomatically = self.resubscribeAutomatically;

src/darwin/Framework/CHIP/MTRDevice.mm

@@ -336,6 +336,7 @@ - (void)unitTestReportEndForDevice:(MTRDevice *)device;
 - (BOOL)unitTestShouldSetUpSubscriptionForDevice:(MTRDevice *)device;
 - (BOOL)unitTestShouldSkipExpectedValuesForWrite:(MTRDevice *)device;
 - (NSNumber *)unitTestMaxIntervalOverrideForSubscription:(MTRDevice *)device;
+- (BOOL)unitTestForceAttributeReportsIfMatchingCache:(MTRDevice *)device;
 @end
 #endif
 
@@ -745,7 +746,7 @@ - (BOOL)_subscriptionAbleToReport
 
     // Unfortunately, we currently have no subscriptions over our hacked-up XPC
     // setup.  Try to detect that situation.
-    if ([_deviceController.class respondsToSelector:@selector(sharedControllerWithID:xpcConnectBlock:)]) {
+    if ([_deviceController isKindOfClass:MTRDeviceControllerOverXPC.class]) {
         return NO;
     }
 
@@ -1603,24 +1604,33 @@ static BOOL AttributeHasChangesOmittedQuality(MTRAttributePath * attributePath)
 - (NSDictionary<NSString *, id> * _Nullable)readAttributeWithEndpointID:(NSNumber *)endpointID
                                                               clusterID:(NSNumber *)clusterID
                                                             attributeID:(NSNumber *)attributeID
-                                                                 params:(MTRReadParams *)params
+                                                                 params:(MTRReadParams * _Nullable)params
 {
     MTRAttributePath * attributePath = [MTRAttributePath attributePathWithEndpointID:endpointID
                                                                            clusterID:clusterID
                                                                          attributeID:attributeID];
 
     BOOL attributeIsSpecified = MTRAttributeIsSpecified(clusterID.unsignedIntValue, attributeID.unsignedIntValue);
-    BOOL hasChangesOmittedQuality = AttributeHasChangesOmittedQuality(attributePath);
+    BOOL hasChangesOmittedQuality;
+    if (attributeIsSpecified) {
+        hasChangesOmittedQuality = AttributeHasChangesOmittedQuality(attributePath);
+    } else {
+        if (params == nil) {
+            hasChangesOmittedQuality = NO;
+        } else {
+            hasChangesOmittedQuality = !params.assumeUnknownAttributesReportable;
+        }
+    }
 
     // Return current known / expected value right away
     NSDictionary<NSString *, id> * attributeValueToReturn = [self _attributeValueDictionaryForAttributePath:attributePath];
 
     // Send read request to device if any of the following are true:
-    // 1. The attribute is not in the specification (so we don't know whether hasChangesOmittedQuality can be trusted).
-    // 2. Subscription not in a state we can expect reports
-    // 3. There is subscription but attribute has Changes Omitted quality
-    // TODO: add option for BaseSubscriptionCallback to report during priming, to reduce when case 4 is hit
-    if (!attributeIsSpecified || ![self _subscriptionAbleToReport] || hasChangesOmittedQuality) {
+    // 1. Subscription not in a state we can expect reports
+    // 2. The attribute has the Changes Omitted quality, so we won't get reports for it.
+    // 3. The attribute is not in the spec, and the read params asks to assume
+    //    an unknown attribute has the Changes Omitted quality.
+    if (![self _subscriptionAbleToReport] || hasChangesOmittedQuality) {
         // Read requests container will be a mutable array of items, each being an array containing:
         //   [attribute request path, params]
         // Batching handler should only coalesce when params are equal.
@@ -2344,6 +2354,18 @@ - (NSArray *)_getAttributesToReportWithReportedValues:(NSArray<NSDictionary<NSSt
             }
             NSArray * expectedValue = _expectedValueCache[attributePath];
 
+            // Unit test only code.
+#ifdef DEBUG
+            if (!readCacheValueChanged) {
+                id delegate = _weakDelegate.strongObject;
+                if (delegate) {
+                    if ([delegate respondsToSelector:@selector(unitTestForceAttributeReportsIfMatchingCache:)]) {
+                        readCacheValueChanged = [delegate unitTestForceAttributeReportsIfMatchingCache:self];
+                    }
+                }
+            }
+#endif // DEBUG
+
             // Report the attribute if a read would get a changed value.  This happens
             // when our cached value changes and no expected value exists.
             if (readCacheValueChanged && !expectedValue) {

src/darwin/Framework/CHIPTests/MTRDeviceTests.m

@@ -1518,6 +1518,10 @@ - (void)test017_TestMTRDeviceBasics
     [self waitForExpectations:@[ onTimeWriteSuccess, onTimePreviousValue ] timeout:10];
 
     // Test if errors are properly received
+    // TODO: We might stop reporting these altogether from MTRDevice, and then
+    // this test will need updating.
+    __auto_type * readThroughForUnknownAttributesParams = [[MTRReadParams alloc] init];
+    readThroughForUnknownAttributesParams.assumeUnknownAttributesReportable = NO;
     XCTestExpectation * attributeReportErrorExpectation = [self expectationWithDescription:@"Attribute read error"];
     delegate.onAttributeDataReceived = ^(NSArray<NSDictionary<NSString *, id> *> * data) {
         for (NSDictionary<NSString *, id> * attributeReponseValue in data) {
@@ -1526,8 +1530,9 @@ - (void)test017_TestMTRDeviceBasics
             }
         }
     };
+
     // use the nonexistent attribute and expect read error
-    [device readAttributeWithEndpointID:testEndpointID clusterID:testClusterID attributeID:testAttributeID params:nil];
+    [device readAttributeWithEndpointID:testEndpointID clusterID:testClusterID attributeID:testAttributeID params:readThroughForUnknownAttributesParams];
     [self waitForExpectations:@[ attributeReportErrorExpectation ] timeout:10];
 
     // Resubscription test setup