`b05a5d0a` added an arity-trimming step to the shared
`ScriptedPythonInterface::Dispatch`: extensions are now allowed to
define methods with trailing parameters as optional
(`num_children(self)` vs. `num_children(self, max_count)`), so before
calling into a method, `Dispatch` needs to know how many positional
arguments it actually accepts and drop any trailing ones we'd otherwise
pass.
That check calls `PythonCallable::GetArgInfo`, which ran a whole
embedded Python script through `inspect.signature` on every call, since
every scripted-extension dispatch goes through it.
For the common case `GetArgInfo()` actually needs to handle fast (plain
Python functions/methods, classes used as constructors, and callable
instances defining `__call__`, i.e. everything `Dispatch<T>()` and
`CreatePluginObject()` ever pass it), the answer is available as plain
data attributes, with no Python bytecode execution required:
`__func__`/`__self__` to unwrap bound methods, and `__code__`'s
`co_argcount`/`co_flags` for the actual positional-argument count and
varargs bit. For a class, that means `__init__` -- except a class may
customize `__new__` instead and leave `__init__` untouched, in which
case `object.__init__` becomes lenient about extra arguments.
Anything else still lacking `__code__` can fall back to the original
`inspect.signature()`-based implementation, now exposed as
`PythonCallable::GetArgInfoFromInspectSignature()` so it can be used
separately.
rdar://183776556
---------
Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>
1ac9b999f8