Project update with UE 5.7 Impossible

Development Programming & Scripting Blueprint
1

Hello, I wanted to open a UE 5.6 project in 5.7, but I get this compilation error message. I can open other projects, but not this one (the most important one!).
Thank you very much for your help.

The project could not be compiled. Would you like to open it in Visual Studio?

Running C:/Program Files/Epic Games/UE_5.7/Engine/Build/BatchFiles/Build.bat Development Win64 -Project=“G:/LIBERIA 5.5 5.6 5.7/LIBERIA.uproject” -TargetType=Editor -Progress -NoEngineChanges -NoHotReloadFromIDE
Using bundled DotNet SDK version: 8.0.412 win-x64
Running UnrealBuildTool: dotnet “…\Engine\Binaries\DotNET\UnrealBuildTool\UnrealBuildTool.dll” Development Win64 -Project=“G:/LIBERIA 5.5 5.6 5.7/LIBERIA.uproject” -TargetType=Editor -Progress -NoEngineChanges -NoHotReloadFromIDE
Log file: C:\Users\Utilisateur\AppData\Local\UnrealBuildTool\Log.txt
Creating makefile for VaubanEditor (no existing makefile)
Warning: [Upgrade]
Warning: [Upgrade] Using backward-compatible build settings. The latest version of UE sets the following values by default, which may require code changes:
Warning: [Upgrade] WindowsPlatform.bStrictInlineConformance = true => Updates MSVC inline conformance (Remove unreferenced COMDAT) to true (Previously: false).
Warning: [Upgrade] UndefinedIdentifierWarningLevel = WarningLevel.Error => Enables compile-time validation of undefined identifiers in conditional expressions. (Previously: Off).
Warning: [Upgrade] Suppress this message by setting ‘DefaultBuildSettings = BuildSettingsVersion.V6;’ in VaubanEditor.Target.cs, and explicitly overriding settings that differ from the new defaults.
Warning: [Upgrade]
Warning: [Upgrade]
Warning: [Upgrade] Using backward-compatible include order. The latest version of UE has changed the order of includes, which may require code changes. The current setting is:
Warning: [Upgrade] IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_4
Warning: [Upgrade] Suppress this message by setting ‘IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_7;’ in VaubanEditor.Target.cs.
Warning: [Upgrade] Alternatively you can set this to ‘EngineIncludeOrderVersion.Latest’ to always use the latest include order. This will potentially cause compile errors when integrating new versions of the engine.
Warning: [Upgrade]
Wrote partial receipt to G:\LIBERIA 5.5 5.6 5.7\Binaries\Win64\VaubanEditor.target
VaubanEditor modifies the values of properties: [ UndefinedIdentifierWarningLevel: Off != Error ]. This is not allowed, as VaubanEditor has build products in common with UnrealEditor.
Remove the modified setting, change VaubanEditor to use a unique build environment by setting ‘BuildEnvironment = TargetBuildEnvironment.Unique;’ in the VaubanEditorTarget constructor, or set bOverrideBuildEnvironment = true to force this setting on.

Result: Failed (OtherCompilationError)
Total execution time: 0.93 seconds

2

I would like to add some information. When I created the UE5.7 project and tried to open it, I got this message:

The last build used an outdated BuildSettingsVersion, or the target still requires upgrading.

Please upgrade VaubanEditor.Target.cs:

Update the build settings version (Installed Engine Build & Source Build):
DefaultBuildSettings = BuildSettingsVersion.V6;

OR

Declare a unique build environment (Source Build only):
BuildEnvironment = TargetBuildEnvironment.Unique;

If you have already updated the target, would you like to rebuild & open the project?

3

Hello there @herve1234!

Checking with my peers, what you got here looks like a migration/update conflict, as the engine is clashing with your project trying to turn off certain warnings (like UndefinedIdentifierWarningLevel: Off). This became a bit more strict in 5.7, and the migrated settings from 5.6 are most likely generating the error.

VaubanEditor modifies the values of properties: [ UndefinedIdentifierWarningLevel: Off != Error ]. This is not allowed, as VaubanEditor has build products in common with UnrealEditor.

In order to fix the issue, go to your main directory, open your .Target.cs file, and add the following to your logic:

DefaultBuildSettings = BuildSettingsVersion.V6;
IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_7;
ExtraModuleNames.Add(“Vauban”);

After the change, close UE and VS, and perform a cache clear to purge any old data from 5.6. To do so, delete folders Binaries, Intermediate, and DerivedDataCache. After that, locate your .uproject file, right click it, and select “Generate Visual Studio project files”. Allow your project to rebuild, then test the compilation again.