Ignore configured session if session description does not exist
A bit of background in gnome-shell#3302 , but since I have modified gnome-session and isolated the failure, it seems appropriate to file new here.
After 3.36 to 3.38 upgrade: I can go via GDM to plasma / plasma wayland, then do "gnome-shell --replace" to run gnome-shell inside plasma, but I cannot go directly from GDM to any of gnome shell variants (wayland /x11 / classic). The fact that "gnome-shell --replace" inside plasma works, and works with all my gnome-shell extensions, means that the gdm->gnome-shell issue I am experiencing is not related to extensions.
I have gotten so fed up with it I finally built a modified version of gnome-session - I commented out all the gsm_fail_whale_dialog_we_failed() and replaced them with g_warning(location), and found it is failing at gsm_session_fill() . It is stuck and do not launch gnome-shell, but I can launch gnome-shell manually in a VT setting DISPLAY to get a functional shell.
The failure is at gsm_session_fill() returning False . What other changes can I try, etc? As I said, I can run gnome-shell --replace, etc so it does not seem to be a gnome-shell extension issue; there are no glaring warnings / errors in journalctl . And I definitely wish there are more g_error() / g_warning() in the code. (and the build instruction too - I went with a rpmbuild -bb after editing the spec file,but could do with a direct build).
Oh, I cannot go directly from GDM to a 4th, the flashback/metacity variant, either.