Emit Leave events before the fabric is actually removed. (#21191)

Otherwise we stop being able to do things like send a report for the
event.

Fixes #13930
Fixes #21012

src/app/clusters/operational-credentials-server/operational-credentials-server.cpp

@@ -325,20 +325,12 @@ void OnPlatformEventHandler(const chip::DeviceLayer::ChipDeviceEvent * event, in
 // As per specifications section 11.22.5.1. Constant RESP_MAX
 constexpr size_t kMaxRspLen = 900;
 
-// TODO: The code currently has two sources of truths for fabrics, the fabricInfo table + the attributes. There should only be one,
-// the attributes list. Currently the attributes are not persisted so we are keeping the fabric table to have the
-// fabrics/admrins be persisted. Once attributes are persisted, there should only be one sorce of truth, the attributes list and
-// only that should be modifed to perosst/read/write fabrics.
-// TODO: Once attributes are persisted, implement reading/writing/manipulation fabrics around that and remove fabricTable
-// logic.
 class OpCredsFabricTableDelegate : public chip::FabricTable::Delegate
 {
 public:
-    // Gets called when a fabric is deleted from KVS store
-    void OnFabricRemoved(const FabricTable & fabricTable, FabricIndex fabricIndex) override
+    // Gets called when a fabric is about to be deleted
+    void FabricWillBeRemoved(const FabricTable & fabricTable, FabricIndex fabricIndex) override
     {
-        ChipLogProgress(Zcl, "OpCreds: Fabric index 0x%x was removed", static_cast<unsigned>(fabricIndex));
-
         // The Leave event SHOULD be emitted by a Node prior to permanently leaving the Fabric.
         for (auto endpoint : EnabledEndpointsWithServerCluster(Basic::Id))
         {
@@ -359,8 +351,14 @@ class OpCredsFabricTableDelegate : public chip::FabricTable::Delegate
         // - removing the fabric removes all associated access control entries, so generating
         //   subsequent reports containing the leave event will fail the access control check.
         InteractionModelEngine::GetInstance()->GetReportingEngine().ScheduleUrgentEventDeliverySync();
-        EventManagement::GetInstance().FabricRemoved(fabricIndex);
+    }
 
+    // Gets called when a fabric is deleted
+    void OnFabricRemoved(const FabricTable & fabricTable, FabricIndex fabricIndex) override
+    {
+        ChipLogProgress(Zcl, "OpCreds: Fabric index 0x%x was removed", static_cast<unsigned>(fabricIndex));
+
+        EventManagement::GetInstance().FabricRemoved(fabricIndex);
         NotifyFabricTableChanged();
     }
 

src/credentials/FabricTable.cpp

@@ -889,6 +889,18 @@ CHIP_ERROR FabricTable::Delete(FabricIndex fabricIndex)
     VerifyOrReturnError(mStorage != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_ARGUMENT);
 
+    {
+        FabricTable::Delegate * delegate = mDelegateListRoot;
+        while (delegate)
+        {
+            // It is possible that delegate will remove itself from the list in FabricWillBeRemoved,
+            // so we grab the next delegate in the list now.
+            FabricTable::Delegate * nextDelegate = delegate->next;
+            delegate->FabricWillBeRemoved(*this, fabricIndex);
+            delegate = nextDelegate;
+        }
+    }
+
     FabricInfo * fabricInfo = GetMutableFabricByIndex(fabricIndex);
     if (fabricInfo == &mPendingFabric)
     {

src/credentials/FabricTable.h

@@ -360,6 +360,13 @@ class DLL_EXPORT FabricTable
         Delegate() {}
         virtual ~Delegate() {}
 
+        /**
+         * Gets called when a fabric is about to be deleted, such as on
+         * FabricTable::Delete().  This allows actions to be taken that need the
+         * fabric to still be around before we delete it.
+         **/
+        virtual void FabricWillBeRemoved(const FabricTable & fabricTable, FabricIndex fabricIndex) {}
+
         /**
          * Gets called when a fabric is deleted, such as on FabricTable::Delete().
          **/