Argument parsing: use VARARGS for *any* function taking **kwds

pyo3-macros-backend/src/method.rs

@@ -1,7 +1,7 @@
 // Copyright (c) 2017-present PyO3 Project and Contributors
 
 use crate::attributes::TextSignatureAttribute;
-use crate::params::{impl_arg_params, is_forwarded_args};
+use crate::params::{accept_args_kwargs, impl_arg_params};
 use crate::pyfunction::PyFunctionOptions;
 use crate::pyfunction::{PyFunctionArgPyO3Attributes, PyFunctionSignature};
 use crate::utils;
@@ -171,10 +171,11 @@ impl CallingConvention {
     /// Different other slots (tp_call, tp_new) can have other requirements
     /// and are set manually (see `parse_fn_type` below).
     pub fn from_args(args: &[FnArg<'_>], attrs: &[Argument]) -> Self {
+        let (_, accept_kwargs) = accept_args_kwargs(attrs);
         if args.is_empty() {
             Self::Noargs
-        } else if is_forwarded_args(args, attrs) {
-            // for f(*args, **kwds), always prefer varargs
+        } else if accept_kwargs {
+            // for functions that accept **kwargs, always prefer varargs
             Self::Varargs
         } else if cfg!(all(Py_3_7, not(Py_LIMITED_API))) {
             Self::Fastcall
@@ -221,21 +222,6 @@ pub fn parse_method_receiver(arg: &syn::FnArg) -> Result<SelfType> {
 }
 
 impl<'a> FnSpec<'a> {
-    /// Determine if the function gets passed a *args tuple or **kwargs dict.
-    pub fn accept_args_kwargs(&self) -> (bool, bool) {
-        let (mut accept_args, mut accept_kwargs) = (false, false);
-
-        for s in &self.attrs {
-            match s {
-                Argument::VarArgs(_) => accept_args = true,
-                Argument::KeywordArgs(_) => accept_kwargs = true,
-                _ => continue,
-            }
-        }
-
-        (accept_args, accept_kwargs)
-    }
-
     /// Parser function signature and function attributes
     pub fn parse(
         sig: &'a mut syn::Signature,

pyo3-macros-backend/src/params.rs

@@ -11,6 +11,21 @@ use syn::ext::IdentExt;
 use syn::spanned::Spanned;
 use syn::Result;
 
+/// Determine if the function gets passed a *args tuple or **kwargs dict.
+pub fn accept_args_kwargs(attrs: &[Argument]) -> (bool, bool) {
+    let (mut accept_args, mut accept_kwargs) = (false, false);
+
+    for s in attrs {
+        match s {
+            Argument::VarArgs(_) => accept_args = true,
+            Argument::KeywordArgs(_) => accept_kwargs = true,
+            _ => continue,
+        }
+    }
+
+    (accept_args, accept_kwargs)
+}
+
 /// Return true if the argument list is simply (*args, **kwds).
 pub fn is_forwarded_args(args: &[FnArg<'_>], attrs: &[Argument]) -> bool {
     args.len() == 2 && is_args(attrs, &args[0].name) && is_kwargs(attrs, &args[1].name)
@@ -112,7 +127,7 @@ pub fn impl_arg_params(
         )?);
     }
 
-    let (accept_args, accept_kwargs) = spec.accept_args_kwargs();
+    let (accept_args, accept_kwargs) = accept_args_kwargs(&spec.attrs);
 
     let cls_name = if let Some(cls) = self_ {
         quote! { Some(<#cls as pyo3::type_object::PyTypeInfo>::NAME) }