Minor cleanup around read/subscribe(To)AttributePaths. (#26171)

1) Use initWithArray:copyItems:YES when copying arrays, instead of hand-rolling
   the copy.
2) For read, empty paths should just lead to an empty result, not an error, just
   like they would if the read actually happened.

Fixes #26169

src/darwin/Framework/CHIP/MTRBaseDevice.h

@@ -287,9 +287,10 @@ MTR_NEWLY_AVAILABLE
  *
  * Lists of attribute and event paths to read can be provided via attributePaths and eventPaths.
  *
- * The completion will be called with an error if the input parameters are invalid (e.g., both attributePaths and eventPaths are
- * empty.) or the entire read interaction fails. Otherwise it will be called with values, which may be empty (e.g. if no paths
- * matched the wildcard paths passed in) or may include per-path errors if particular paths failed.
+ * The completion will be called with an error if the entire read interaction fails. Otherwise it
+ * will be called with an array of values. This array may be empty (e.g. if no paths matched the
+ * wildcard paths passed in, or if empty lists of paths were passed in) or may include per-path
+ * errors if particular paths failed.
  *
  * If the sum of the lengths of attributePaths and eventPaths exceeds 9, the read may fail due to the device not supporting that
  * many read paths.
@@ -394,8 +395,8 @@ MTR_NEWLY_AVAILABLE
  *
  * Lists of attribute and event paths to subscribe to can be provided via attributePaths and eventPaths.
  *
- * The reportHandler will be called with an error if the inputs are invalid (e.g., both attributePaths and eventPaths are
- * empty), or if the subscription fails entirely.
+ * The reportHandler will be called with an error if the subscription fails
+ * entirely (including when both attributePaths and eventPaths are empty).
  *
  * The reportHandler will be called with arrays of response-value dictionaries
  * (which may be data or errors) as path-specific data is received.

src/darwin/Framework/CHIP/MTRBaseDevice.mm

@@ -917,26 +917,21 @@ - (void)readAttributePaths:(NSArray<MTRAttributeRequestPath *> * _Nullable)attri
                 completion:(MTRDeviceResponseHandler)completion
 {
     if ((attributePaths == nil || [attributePaths count] == 0) && (eventPaths == nil || [eventPaths count] == 0)) {
+        // No paths, just return an empty array.
         dispatch_async(queue, ^{
-            completion(nil, [MTRError errorForCHIPErrorCode:CHIP_ERROR_INVALID_ARGUMENT]);
+            completion(@[], nil);
         });
         return;
     }
 
-    NSMutableArray<MTRAttributeRequestPath *> * attributes = nil;
+    NSArray<MTRAttributeRequestPath *> * attributes = nil;
     if (attributePaths != nil) {
-        attributes = [[NSMutableArray alloc] init];
-        for (MTRAttributeRequestPath * attributePath in attributePaths) {
-            [attributes addObject:[attributePath copy]];
-        }
+        attributes = [[NSArray alloc] initWithArray:attributePaths copyItems:YES];
     }
 
-    NSMutableArray<MTREventRequestPath *> * events = nil;
+    NSArray<MTREventRequestPath *> * events = nil;
     if (eventPaths != nil) {
-        events = [[NSMutableArray alloc] init];
-        for (MTRAttributeRequestPath * eventPath in eventPaths) {
-            [events addObject:[eventPath copy]];
-        }
+        events = [[NSArray alloc] initWithArray:eventPaths copyItems:YES];
     }
     params = (params == nil) ? nil : [params copy];
     auto * bridge = new MTRDataValueDictionaryCallbackBridge(queue, completion,
@@ -1006,9 +1001,9 @@ - (void)readAttributePaths:(NSArray<MTRAttributeRequestPath *> * _Nullable)attri
             chip::app::ReadPrepareParams readParams(session);
             [params toReadPrepareParams:readParams];
             readParams.mpAttributePathParamsList = attributePathParamsList.Get();
-            readParams.mAttributePathParamsListSize = [attributePaths count];
+            readParams.mAttributePathParamsListSize = [attributes count];
             readParams.mpEventPathParamsList = eventPathParamsList.Get();
-            readParams.mEventPathParamsListSize = [eventPaths count];
+            readParams.mEventPathParamsListSize = [events count];
 
             AttributePathParams * attributePathParamsListToFree = attributePathParamsList.Get();
             EventPathParams * eventPathParamsListToFree = eventPathParamsList.Get();
@@ -1288,8 +1283,10 @@ - (void)subscribeToAttributePaths:(NSArray<MTRAttributeRequestPath *> * _Nullabl
           resubscriptionScheduled:(MTRDeviceResubscriptionScheduledHandler _Nullable)resubscriptionScheduled
 {
     if ((attributePaths == nil || [attributePaths count] == 0) && (eventPaths == nil || [eventPaths count] == 0)) {
+        // Per spec a server would respond InvalidAction to this, so just go
+        // ahead and do that.
         dispatch_async(queue, ^{
-            reportHandler(nil, [MTRError errorForCHIPErrorCode:CHIP_ERROR_INVALID_ARGUMENT]);
+            reportHandler(nil, [MTRError errorForIMStatus:StatusIB(Status::InvalidAction)]);
         });
         return;
     }
@@ -1303,20 +1300,14 @@ - (void)subscribeToAttributePaths:(NSArray<MTRAttributeRequestPath *> * _Nullabl
     }
 
     // Copy params before going async.
-    NSMutableArray<MTRAttributeRequestPath *> * attributes = nil;
+    NSArray<MTRAttributeRequestPath *> * attributes = nil;
     if (attributePaths != nil) {
-        attributes = [[NSMutableArray alloc] init];
-        for (MTRAttributeRequestPath * attributePath in attributePaths) {
-            [attributes addObject:[attributePath copy]];
-        }
+        attributes = [[NSArray alloc] initWithArray:attributePaths copyItems:YES];
     }
 
-    NSMutableArray<MTREventRequestPath *> * events = nil;
+    NSArray<MTREventRequestPath *> * events = nil;
     if (eventPaths != nil) {
-        events = [[NSMutableArray alloc] init];
-        for (MTRAttributeRequestPath * eventPath in eventPaths) {
-            [events addObject:[eventPath copy]];
-        }
+        events = [[NSArray alloc] initWithArray:eventPaths copyItems:YES];
     }
 
     params = (params == nil) ? nil : [params copy];