I'm using XCode 26.2 and I have the same problem as you. Is this apparently HORRIBLE bug documented anywhere?

I think the .plist has to have some references to the help Book.

Example of the code you use to call AppTransaction?

So ClassName would be AppTransaction? XCode won't build this: "Use of undeclared identifier 'AppTransaction'"

This morning my playgrounds started to work again. Oi vey indeed...

I preprocessed some simple .c and .m files with a few functions and headers. The preprocessed files have the function declarations, enums, etc. in them but no errors are reported. Then they won't build with the same weird errors. This looks like a problem with the build system in XCode.

I misunderstood what you said. I preprocessed some .m and .c files and I don't see any errors in them but they still won't build.

Preprocessing the file reports the errors. XCode doesn't even get to the build phase before it encounters the fatal errors. Yes, I have been programming with C for a while - on the Mac since about 1998. On, a somewhat positive note, I sent an example of a project that won't build to DTS. They have it and it won't build for them either. Engineers at Apple are trying to see what XCode is doing to me.

Thank you so much for trying to help me with this baffling problem. Searching the XCode documentation and IDE I don't see where I can display the preprocessor's output. Where is it?

This horrible bug is still not fixed FIVE YEARS LATER. Any time I open an xib, XCode will report a spurious error for at least one NSTextField. There's no way to fix this or suppress the error.

This is still broken this morning. There are two problems: The server that provides an App Store test receipt to XCode is broken, as usual. XCode needs to fetch a new receipt when you clear the build folder or build a new version but NOT when you just change a few lines of code. I am appalled that Apple wouldn't fix this after years of trouble for developers.

I worked on some other code and ran my project again and now it works. ????

May 20, 2022, XCode 13.4, macOS 12.3.1 - YES THIS IS BROKEN AGAIN! I can't submit an update to the App Store.

This horrible bug has occurred on and off for years so it's not surprising that it would be in a new version of XCode/App Store. All you can do is file a bug report.

This has been broken for TWO MONTHS. How can I submit an update at the App Store?