Fix AttributeCache forwarding callback

* Fix forwarded OnAttributeData callback losing data by
  copying the TLV reader before its state changes for cache update.

src/app/AttributeCache.cpp

@@ -115,12 +115,19 @@ void AttributeCache::OnAttributeData(const ConcreteDataAttributePath & aPath, TL
     //
     VerifyOrDie(!aPath.IsListItemOperation());
 
+    // Copy the reader for forwarding
+    TLV::TLVReader dataSnapshot;
+    if (apData)
+    {
+        dataSnapshot.Init(*apData);
+    }
+
     UpdateCache(aPath, apData, aStatus);
 
     //
     // Forward the call through.
     //
-    mCallback.OnAttributeData(aPath, apData, aStatus);
+    mCallback.OnAttributeData(aPath, apData ? &dataSnapshot : nullptr, aStatus);
 }
 
 CHIP_ERROR AttributeCache::Get(const ConcreteAttributePath & path, TLV::TLVReader & reader)

src/app/tests/TestAttributeCache.cpp

@@ -105,21 +105,76 @@ uint8_t AttributeInstruction::sInstructionId = 0;
 
 using AttributeInstructionListType = std::vector<AttributeInstruction>;
 
+class ForwardedDataCallbackValidator final
+{
+public:
+    void SetExpectation(TLV::TLVReader & aData, EndpointId endpointId, AttributeInstruction::AttributeType attributeType)
+    {
+        auto length = aData.GetRemainingLength();
+        std::vector<uint8_t> buffer(aData.GetReadPoint(), aData.GetReadPoint() + length);
+        if (!mExpectedBuffers.empty() && endpointId == mLastEndpointId && attributeType == mLastAttributeType)
+        {
+            // For overriding test, the last buffered data is removed.
+            mExpectedBuffers.pop_back();
+        }
+        mExpectedBuffers.push_back(buffer);
+        mLastEndpointId    = endpointId;
+        mLastAttributeType = attributeType;
+    }
+
+    void SetExpectation() { mExpectedBuffers.clear(); }
+
+    void ValidateData(TLV::TLVReader & aData, bool isListOperation)
+    {
+        NL_TEST_ASSERT(gSuite, !mExpectedBuffers.empty());
+        if (!mExpectedBuffers.empty() > 0)
+        {
+            auto buffer = mExpectedBuffers.front();
+            mExpectedBuffers.erase(mExpectedBuffers.begin());
+            uint32_t length = static_cast<uint32_t>(buffer.size());
+            if (isListOperation)
+            {
+                // List operation will attach end of container
+                NL_TEST_ASSERT(gSuite, length < aData.GetRemainingLength());
+            }
+            else
+            {
+                NL_TEST_ASSERT(gSuite, length == aData.GetRemainingLength());
+            }
+            if (length <= aData.GetRemainingLength() && length > 0)
+            {
+                NL_TEST_ASSERT(gSuite, std::memcmp(aData.GetReadPoint(), buffer.data(), length) == 0);
+                if (std::memcmp(aData.GetReadPoint(), buffer.data(), length) != 0)
+                {
+                    ChipLogProgress(DataManagement, "Failed");
+                }
+            }
+        }
+    }
+
+    void ValidateNoData() { NL_TEST_ASSERT(gSuite, mExpectedBuffers.empty()); }
+
+private:
+    std::vector<std::vector<uint8_t>> mExpectedBuffers;
+    EndpointId mLastEndpointId;
+    AttributeInstruction::AttributeType mLastAttributeType;
+};
+
 class DataSeriesGenerator
 {
 public:
     DataSeriesGenerator(ReadClient::Callback * readCallback, AttributeInstructionListType & instructionList) :
         mReadCallback(readCallback), mInstructionList(instructionList)
     {}
 
-    void Generate();
+    void Generate(ForwardedDataCallbackValidator & dataCallbackValidator);
 
 private:
     ReadClient::Callback * mReadCallback;
     AttributeInstructionListType & mInstructionList;
 };
 
-void DataSeriesGenerator::Generate()
+void DataSeriesGenerator::Generate(ForwardedDataCallbackValidator & dataCallbackValidator)
 {
     System::PacketBufferHandle handle;
     System::PacketBufferTLVWriter writer;
@@ -197,12 +252,14 @@ void DataSeriesGenerator::Generate()
             writer.Finalize(&handle);
             reader.Init(std::move(handle));
             NL_TEST_ASSERT(gSuite, reader.Next() == CHIP_NO_ERROR);
+            dataCallbackValidator.SetExpectation(reader, instruction.mEndpointId, instruction.mAttributeType);
             callback->OnAttributeData(path, &reader, status);
         }
         else
         {
             ChipLogProgress(DataManagement, "\t -- Generating Status");
             status.mStatus = Protocols::InteractionModel::Status::Failure;
+            dataCallbackValidator.SetExpectation();
             callback->OnAttributeData(path, nullptr, status);
         }
 
@@ -215,12 +272,34 @@ void DataSeriesGenerator::Generate()
 class CacheValidator : public AttributeCache::Callback
 {
 public:
-    CacheValidator(AttributeInstructionListType & instructionList);
+    CacheValidator(AttributeInstructionListType & instructionList, ForwardedDataCallbackValidator & dataCallbackValidator);
 
     Clusters::TestCluster::Attributes::TypeInfo::DecodableType clusterValue;
 
 private:
     void OnDone() override {}
+    void OnAttributeData(const ConcreteDataAttributePath & aPath, TLV::TLVReader * apData, const StatusIB & aStatus) override
+    {
+        ChipLogProgress(DataManagement, "\t\t -- Validating OnAttributeData callback");
+        // Ensure that the provided path is one that we're expecting to find
+        auto iter = mExpectedAttributes.find(aPath);
+        NL_TEST_ASSERT(gSuite, iter != mExpectedAttributes.end());
+
+        if (aStatus.IsSuccess())
+        {
+            // Verify that the apData is passed as nonnull
+            NL_TEST_ASSERT(gSuite, apData != nullptr);
+            if (apData)
+            {
+                mDataCallbackValidator.ValidateData(*apData, aPath.IsListOperation());
+            }
+        }
+        else
+        {
+            mDataCallbackValidator.ValidateNoData();
+        }
+    }
+
     void DecodeAttribute(const AttributeInstruction & instruction, const ConcreteAttributePath & path, AttributeCache * cache)
     {
         CHIP_ERROR err;
@@ -431,9 +510,13 @@ class CacheValidator : public AttributeCache::Callback
     std::set<ConcreteAttributePath> mExpectedAttributes;
     std::set<std::tuple<EndpointId, ClusterId>> mExpectedClusters;
     std::set<EndpointId> mExpectedEndpoints;
+
+    ForwardedDataCallbackValidator & mDataCallbackValidator;
 };
 
-CacheValidator::CacheValidator(AttributeInstructionListType & instructionList)
+CacheValidator::CacheValidator(AttributeInstructionListType & instructionList,
+                               ForwardedDataCallbackValidator & dataCallbackValidator) :
+    mDataCallbackValidator(dataCallbackValidator)
 {
     for (auto & instruction : instructionList)
     {
@@ -452,10 +535,11 @@ CacheValidator::CacheValidator(AttributeInstructionListType & instructionList)
 
 void RunAndValidateSequence(AttributeInstructionListType list)
 {
-    CacheValidator client(list);
+    ForwardedDataCallbackValidator dataCallbackValidator;
+    CacheValidator client(list, dataCallbackValidator);
     AttributeCache cache(client);
     DataSeriesGenerator generator(&cache.GetBufferedCallback(), list);
-    generator.Generate();
+    generator.Generate(dataCallbackValidator);
 }
 
 /*