Display a warning for when we fail to write to the settings file (#7950)

We wrap the call to `_WriteSettings` in
`CascadiaSettingsSerialization.cpp` in a try/catch block, and if we
catch an error we append a warning telling the user to check the
permissions on their settings file. 

Closes #7727

src/cascadia/TerminalApp/AppLogic.cpp

@@ -40,7 +40,8 @@ static const std::array<std::wstring_view, static_cast<uint32_t>(SettingsLoadWar
     USES_RESOURCE(L"TooManyKeysForChord"),
     USES_RESOURCE(L"MissingRequiredParameter"),
     USES_RESOURCE(L"LegacyGlobalsProperty"),
-    USES_RESOURCE(L"FailedToParseCommandJson")
+    USES_RESOURCE(L"FailedToParseCommandJson"),
+    USES_RESOURCE(L"FailedToWriteToSettings")
 };
 static const std::array<std::wstring_view, static_cast<uint32_t>(SettingsLoadErrors::ERRORS_SIZE)> settingsLoadErrorsLabels {
     USES_RESOURCE(L"NoProfilesText"),

src/cascadia/TerminalApp/Resources/en-US/Resources.resw

@@ -469,4 +469,7 @@
   <data name="CouldNotOpenUriDialog.PrimaryButtonText" xml:space="preserve">
     <value>Cancel</value>
   </data>
+  <data name="FailedToWriteToSettings" xml:space="preserve">
+    <value>We could not write to your settings file. Check the permissions on that file to ensure that the read-only flag is not set and that write access is granted.</value>
+  </data>
 </root>

src/cascadia/TerminalSettingsModel/CascadiaSettings.cpp

@@ -157,6 +157,16 @@ IVectorView<winrt::Microsoft::Terminal::Settings::Model::SettingsLoadWarnings> C
     return _warnings.GetView();
 }
 
+void CascadiaSettings::ClearWarnings()
+{
+    _warnings.Clear();
+}
+
+void CascadiaSettings::AppendWarning(SettingsLoadWarnings warning)
+{
+    _warnings.Append(warning);
+}
+
 winrt::Windows::Foundation::IReference<winrt::Microsoft::Terminal::Settings::Model::SettingsLoadErrors> CascadiaSettings::GetLoadingError()
 {
     return _loadError;
@@ -179,8 +189,6 @@ winrt::hstring CascadiaSettings::GetSerializationErrorMessage()
 // - <none>
 void CascadiaSettings::_ValidateSettings()
 {
-    _warnings.Clear();
-
     // Make sure to check that profiles exists at all first and foremost:
     _ValidateProfilesExist();
 

src/cascadia/TerminalSettingsModel/CascadiaSettings.h

@@ -83,6 +83,8 @@ namespace winrt::Microsoft::Terminal::Settings::Model::implementation
         Model::ColorScheme GetColorSchemeForProfile(const guid profileGuid) const;
 
         Windows::Foundation::Collections::IVectorView<SettingsLoadWarnings> Warnings();
+        void ClearWarnings();
+        void AppendWarning(SettingsLoadWarnings warning);
         Windows::Foundation::IReference<SettingsLoadErrors> GetLoadingError();
         hstring GetSerializationErrorMessage();
 

src/cascadia/TerminalSettingsModel/CascadiaSettingsSerialization.cpp

@@ -106,6 +106,7 @@ winrt::Microsoft::Terminal::Settings::Model::CascadiaSettings CascadiaSettings::
     {
         auto settings = LoadDefaults();
         auto resultPtr = winrt::get_self<CascadiaSettings>(settings);
+        resultPtr->ClearWarnings();
 
         // GH 3588, we need this below to know if the user chose something that wasn't our default.
         // Collect it up here in case it gets modified by any of the other layers between now and when
@@ -185,7 +186,14 @@ winrt::Microsoft::Terminal::Settings::Model::CascadiaSettings CascadiaSettings::
             // We should re-parse, but not re-layer
             resultPtr->_ParseJsonString(resultPtr->_userSettingsString, false);
 
-            _WriteSettings(resultPtr->_userSettingsString);
+            try
+            {
+                _WriteSettings(resultPtr->_userSettingsString);
+            }
+            catch (...)
+            {
+                resultPtr->AppendWarning(SettingsLoadWarnings::FailedToWriteToSettings);
+            }
         }
 
         // If this throws, the app will catch it and use the default settings

src/cascadia/TerminalSettingsModel/TerminalWarnings.idl

@@ -17,6 +17,7 @@ namespace Microsoft.Terminal.Settings.Model
         MissingRequiredParameter = 7,
         LegacyGlobalsProperty = 8,
         FailedToParseCommandJson = 9,
+        FailedToWriteToSettings = 10,
         WARNINGS_SIZE // IMPORTANT: This MUST be the last value in this enum. It's an unused placeholder.
     };