UBT GenerateClangDatabase is NOT incremental and recreates whole compile_commands.json each time

Development Platform & Builds
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4

I haven’t tested it for a while, but it seems they improved a lot of stuff in GenerateClangDatabase. Perhaps there was a bug that was always forcing full recompilation and -NoExecCodeGenActions was a simple workaround.

Looking through the code, it was always meant to be incremental, so I’m not sure why it wasn’t working for me back in 5.4.2:

if (bExecCodeGenActions)
{
	// Filter all the actions to execute
	HashSet<FileItem> PrerequisiteItems = new HashSet<FileItem>(Makefile.Actions.SelectMany(x => x.ProducedItems).Where(x => x.HasExtension(".h") || x.HasExtension(".cpp") || x.HasExtension(".cc") || x.HasExtension(".c")));
	List<LinkedAction> PrerequisiteActions = ActionGraph.GatherPrerequisiteActions(Actions, PrerequisiteItems);

	Utils.ExecuteCustomBuildSteps(Makefile.PreBuildScripts, Logger);

	// Execute code generation actions
	if (PrerequisiteActions.Any())
	{
		Logger.LogInformation("Executing actions that produce source files...");
		await ActionGraph.ExecuteActionsAsync(BuildConfiguration, PrerequisiteActions, new List<TargetDescriptor> { TargetDescriptor }, Logger);
	}
}