Avoid exception in observable IndexOf implementation (#1017)

Author: kennykerr

strings/base_collections_vector.h

@@ -115,15 +115,26 @@ namespace winrt::impl
 
         bool IndexOf(Windows::Foundation::IInspectable const& value, uint32_t& index) const
         {
-            try
+            if constexpr (is_com_interface_v<T>)
             {
-                return IndexOf(unbox_value<T>(value), index);
+                if (!value)
+                {
+                    return base_type::IndexOf(nullptr, index);
+                }
+                else if (auto as = value.try_as<T>())
+                {
+                    return base_type::IndexOf(as, index);
+                }
             }
-            catch (hresult_no_interface const&)
+            else
             {
-                index = 0;
-                return false;
+                if (auto as = value.try_as<T>())
+                {
+                    return base_type::IndexOf(as.value(), index);
+                }
             }
+
+            return false;
         }
 
         using base_type::GetMany;

test/test/observable_index_of.cpp

@@ -0,0 +1,37 @@
+#include "pch.h"
+
+using namespace winrt;
+using namespace Windows::Foundation;
+using namespace Windows::Foundation::Collections;
+
+TEST_CASE("observable_index_of")
+{
+    {
+        auto v = single_threaded_observable_vector<int>().as<IVector<IInspectable>>();
+        v.Append(box_value(123));
+        uint32_t index = 0;
+        REQUIRE(v.IndexOf(box_value(123), index));
+        REQUIRE(!v.IndexOf(nullptr, index));
+        REQUIRE(!v.IndexOf(box_value(456), index));
+        REQUIRE(!v.IndexOf(Uri(L"http://kennykerr.ca"), index));
+    }
+    {
+        auto value = Uri(L"http://kennykerr.ca");
+
+        auto v = single_threaded_observable_vector<IStringable>().as<IVector<IInspectable>>();
+        v.Append(value);
+        uint32_t index = 0;
+        REQUIRE(v.IndexOf(value, index));
+        REQUIRE(!v.IndexOf(nullptr, index));
+        REQUIRE(!v.IndexOf(box_value(456), index));
+        REQUIRE(!v.IndexOf(Uri(L"http://kennykerr.ca"), index));
+    }
+    {
+        auto v = single_threaded_observable_vector<IStringable>().as<IVector<IInspectable>>();
+        v.Append(nullptr);
+        uint32_t index = 0;
+        REQUIRE(v.IndexOf(nullptr, index));
+        REQUIRE(!v.IndexOf(box_value(456), index));
+        REQUIRE(!v.IndexOf(Uri(L"http://kennykerr.ca"), index));
+    }
+}

test/test/test.vcxproj

@@ -417,6 +417,7 @@
     <ClCompile Include="notify_awaiter.cpp" />
     <ClCompile Include="no_make_detection.cpp" />
     <ClCompile Include="numerics.cpp" />
+    <ClCompile Include="observable_index_of.cpp" />
     <ClCompile Include="out_params.cpp" />
     <ClCompile Include="out_params_abi.cpp" />
     <ClCompile Include="out_params_bad.cpp" />