added label "ResourceKey" to trace details when resource is not found

[TysonMN]

Fixes #2956

Summary of issue

When targeting .NET Framework, not finding a ResourceDictionary key named someKey causes

System.Windows.ResourceDictionary Warning: 9 : Resource not found; ResourceKey='someKey'

to be written to PresentationTraceSources.ResourceDictionarySource, but when targeting .NET Core, that message is only

System.Windows.ResourceDictionary Warning: 9 : Resource not found

Contribution

This branch contributes a fix. I want to explain both why it is a fix and why (I think) it is the correct fix.

A fix

The change adds "ResourceKey" to a string array. That array is later passed into

wpf/src/Microsoft.DotNet.Wpf/src/WindowsBase/MS/Internal/AvTrace.cs

Lines 256 to 261 in b152272

	// Trace an event
	//
	// note: labels start at index 1, parameters start at index 0
	//
	public void Trace( TraceEventType type, int eventId, string message, string[] labels, object[] parameters )

as the labels argument. With the code currently in master, the relevant arguments for the cases in question are

• labels = new string[] { "Resource not found" } and
• parameters = new object[] { "someKey" }.

Confusingly, the first argument in that array is the same as the message argument, so the first entry in labels is ignored in this function. As the comment points out, note: labels start at index 1, parameters start at index 0. Then the body of this for-loop is never executed.

wpf/src/Microsoft.DotNet.Wpf/src/WindowsBase/MS/Internal/AvTrace.cs

Lines 281 to 287 in b152272

	int i = 1, j = 0;
	for( ; i < labels.Length && j < parameters.Length; i++, j++ )
	{
	// Append to the format string a "; {0} = '{1}'", where the index increments (e.g. the second iteration will
	// produce {2} & {3}).
	traceBuilder.Append("; {" + (formatIndex++).ToString() + "}='{" + (formatIndex++).ToString() + "}'" );

With my change, the relevant arguments are

• labels = new string[] { "Resource not found", "ResourceKey" } and
• parameters = new object[] { "someKey" }.

The body of the for-loop executes once to append ; ResourceKey='someKey' to traceBuilder.

Correct fix

No unintended consequences

A concern with any bug fix is that it doesn't only fix the bug in question but also has some unintended consequence. I don't think my change has any unintended consequences. The line I changed alters the definition of TraceResourceDictionary.ResourceNotFound. According to my searches, the only two references to that property are these two, which both lead to the code to which I linked in the previous section and the behavior I described there.

wpf/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/FrameworkElement.cs

Lines 1147 to 1158 in b152272

	if ((fe != null && fe.IsLoaded) || (fce != null && fce.IsLoaded))
	{
	TraceResourceDictionary.Trace( TraceEventType.Warning,
	TraceResourceDictionary.ResourceNotFound,
	resourceKey );
	}
	else if( TraceResourceDictionary.IsEnabled )
	{
	TraceResourceDictionary.TraceActivityItem(
	TraceResourceDictionary.ResourceNotFound,
	resourceKey );
	}

Comparison with .NET Framework source

I tried to analyze the same code in .NET Framework and statically verify what I know to be true via testing, which is that .NET Framework does not contain the bug in question. I didn't quite succeed though. Considering the reference source, I tracked down the same two calls to TraceResourceDictionary.ResourceNotFound, but I wasn't able to find TraceResourceDictionary in the reference source.

Generated?

I am concerned that the change I made is in a file that is in a folder called Generated. Did I edit generated code?

[ryalanms]

Thank you for your contribution, @TysonMN.