Env

DataConfig put most global state into a stack of FDcEnv:

// DataConfigCore/Public/DataConfig/DcEnv.h
struct DATACONFIGCORE_API FDcEnv
{
    TArray<FDcDiagnostic> Diagnostics;

    TSharedPtr<IDcDiagnosticConsumer> DiagConsumer;

    TArray<FDcReader*> ReaderStack;
    TArray<FDcWriter*> WriterStack;

    bool bExpectFail = false;   // mute debug break

    FDcDiagnostic& Diag(FDcErrorCode InErr);

    void FlushDiags();

    FORCEINLINE FDcDiagnostic& GetLastDiag() 
    {
        checkf(Diagnostics.Num(), TEXT("<empty diagnostics>"));
        return Diagnostics.Last();
    }

    ~FDcEnv();
};

DataConfig needs explicit initializatioon before use. This is done through manually DcStartUp(). There's also a paired DcShutdown() that should be called when DataConfig isn't used anymore. Here's an example:

// DataConfigEngineExtra/Private/DcEngineExtraModule.cpp
void FDcEngineExtraModule::StartupModule()
{
    UE_LOG(LogDataConfigCore, Log, TEXT("DcEngineExtraModule module starting up"));
    DcRegisterDiagnosticGroup(&DcDExtra::Details);
    DcRegisterDiagnosticGroup(&DcDEngineExtra::Details);

    DcStartUp(EDcInitializeAction::Minimal);
    //...
}

void FDcEngineExtraModule::ShutdownModule()
{
    DcShutDown();
    //...
}

The active FDcEnv is accessed by calling global function DcEnv(). Inside the Env:

• Diagnostics: all diagnostics are flushed into env.
• DiagConsumer: diagnostic handler, format and print diagnostic to log or MessageLog or even on screen.
• ReaderStack/WriterStack: used to pass along reader/writer down the callstack. See FScopedStackedReader uses for example.
• ... and everything else.

You can use DcPushEnv() to create new env then destroy it calling DcPopEnv(). At this moment it's mostly used to handle reentrant during serialization. See FDcScopedEnv uses for examples.