2.99 ScriptFu scripts having a file argument (SF_DIRNAME) appear in PDB having string argument type instead of GFile
An example is plug-ins/script-fu/contactsheet.scm
GIMP 2 plugins did take a string i.e. type gchararray, but GIMP 3 plugins take a GFile.
It makes little difference for authors of scripts, they still code in Scheme strings to pass or receive a file or dir. But for consistency in the PDB, ScriptFu plugins should have argument type GFile for formal specification of their arguments.
In the code, the problem is in the scriptfu C language code that parses a declarative Scheme list of formal argument specs. The code should translate the ScriptFu constant SF_DIRNAME and SF_FILENAME to the PDB type GFile instead of gchararray, when executing a call to (script-fu-register (....(SF_DIRNAME ...) ...))