Game/plugin shared loading phase problem.

Development Pipeline & Plugins Plugins
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1

I created a new project to create some custom animation nodes.
For these animation nodes to work, the editor module loading phase needs to be PreDefault.

    {
      "Name": "RBAnimResearchEditor",
      "Type": "Developer",
      "LoadingPhase": "PreDefault"
    }

No worries there.

Later, I added a added a marketplace plugin that adds its own custom animation node, and thus also needs its loading phase set to PreDefault.

    {
      "Name": "MirrorAnimationSystemEditor",
      "Type": "Editor",
      "LoadingPhase": "PreDefault",
      "BlacklistPlatforms": [
        "IOS"
      ]
    }

Both work in editor, but upon restarting, the engine fails to fine /Script/MirrorAnimationSystemEditor in time, since the game module is loaded before the plugin.

Tracked the issue down to FEngineLoop::LoadStartupModules():

bool FEngineLoop::LoadStartupModules()
{
	FScopedSlowTask SlowTask(3);

	SlowTask.EnterProgressFrame(1);
	// Load any modules that want to be loaded before default modules are loaded up.
	if (!IProjectManager::Get().LoadModulesForProject(ELoadingPhase::PreDefault) || !IPluginManager::Get().LoadModulesForEnabledPlugins(ELoadingPhase::PreDefault))
	{
		return false;
	}

If I load the plugins BEFORE the game module, the problem is solved:

bool FEngineLoop::LoadStartupModules()
{
	FScopedSlowTask SlowTask(3);

	SlowTask.EnterProgressFrame(1);
	// Load plugins BEFORE game module.
	// Load any modules that want to be loaded before default modules are loaded up.
	if (!IPluginManager::Get().LoadModulesForEnabledPlugins(ELoadingPhase::PreDefault) || !IProjectManager::Get().LoadModulesForProject(ELoadingPhase::PreDefault))
	{
		return false;
	}

I was unable to come across any mention of this issue thus far.
If this doesn’t cause any issues with the our proper project (packaged or otherwise), I’ll make a PR for it.
Please note that I checked FEngineLoop::LoadStartupModules() in the UE4.17.1 release and it is the same as UE4.16.

Thanks.