Adding my experience to this thread as well. 4.26->5.0.0.
We had a very large number of blueprint structs in our project, many of which were nested structs. Many of our game’s blueprint actors, data-tables, anim blueprints all had references to these structs which made the prospect of going through and recreating all of them from scratch or manually updating the references not really a feasible option.
What I did that worked was the following:
-
go through all of our structs one by one and replace the data-type of each struct field with boolean if it was anything other than an engine default type (arrays were left as arrays and so-on).
-
After all the structs were updated I excited the editor and chose DO NOT SAVE when prompted to re-save all the assets in the project that referenced the structs that were modified.
-
Right click on the UProject and Switch Unreal Version to 5.0, followed by right clicking on the UProject again and Generating Visual Studio Project files.
-
Open VS 2019 and Build [Project Name]
-
Open the Uproject to launch UE5.
-
Almost all blueprints fail to compile, but the project actually opens rather than crashing on startup, and all blueprint editors can be opened.
-
In UE5 go through all structs one by one with an old copy of the project in UE4.26 open at the same time to change the data types back to what they were originally. The UE5 struct editor has a compilation warning at the top of the screen that would sometimes say that the struct failed to compile, when this happens I would expand whatever struct field was causing the problem and uncheck the editable checkbox and then re-check it.
7.5 There was one instance where changing the variable type from a boolean back to what it was before (in this case it was a Vector2d originally) caused the engine to crash. To solve that problem I just created a new variable, deleted the old one and then re-named it back to what it was originally.
-
Once all of the structs were renamed I closed the engine and once again selected DO NOT SAVE when prompted to re-save all of the otherwise modified assets that used the structs.
-
Upon relaunching the editor I validated all of the blueprints and went in and refreshed the nodes that were not able to be fixed automatically. Of the thousands of references to these structs in the project, I had to make 5 or so manual changes. No changes to the data-tables or anim blueprints or variable types inside of blueprint actors were required.