From ea9da80ab181a30651db77eaf456544ddc002c67 Mon Sep 17 00:00:00 2001
From: Georg Brandl <georg@python.org>
Date: Sun, 20 Nov 2022 08:48:47 +0100
Subject: [PATCH] macros: fix the check for applying `METH_NOARGS`

to only consider the Python argument list.

Fixes #2750
---
 newsfragments/2760.fixed.md                     | 2 ++
 pyo3-macros-backend/src/method.rs               | 9 +++++++--
 pyo3-macros-backend/src/pyfunction/signature.rs | 9 +++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 newsfragments/2760.fixed.md

diff --git a/newsfragments/2760.fixed.md b/newsfragments/2760.fixed.md
new file mode 100644
index 00000000..65f543e6
--- /dev/null
+++ b/newsfragments/2760.fixed.md
@@ -0,0 +1,2 @@
+Also apply the `NOARGS` argument convention to methods that have a single
+`py: Python` argument.
diff --git a/pyo3-macros-backend/src/method.rs b/pyo3-macros-backend/src/method.rs
index 742f50d4..32df7e6c 100644
--- a/pyo3-macros-backend/src/method.rs
+++ b/pyo3-macros-backend/src/method.rs
@@ -200,7 +200,7 @@ 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_signature(signature: &FunctionSignature<'_>) -> Self {
-        if signature.arguments.is_empty() {
+        if signature.python_signature.has_no_args() {
             Self::Noargs
         } else if signature.python_signature.accepts_kwargs {
             // for functions that accept **kwargs, always prefer varargs
@@ -457,7 +457,12 @@ impl<'a> FnSpec<'a> {
 
         Ok(match self.convention {
             CallingConvention::Noargs => {
-                let call = rust_call(vec![]);
+                let call = if !self.signature.arguments.is_empty() {
+                    // Only `py` arg can be here
+                    rust_call(vec![quote!(#py)])
+                } else {
+                    rust_call(vec![])
+                };
                 quote! {
                     unsafe fn #ident<'py>(
                         #py: _pyo3::Python<'py>,
diff --git a/pyo3-macros-backend/src/pyfunction/signature.rs b/pyo3-macros-backend/src/pyfunction/signature.rs
index e66f14bc..df73fe12 100644
--- a/pyo3-macros-backend/src/pyfunction/signature.rs
+++ b/pyo3-macros-backend/src/pyfunction/signature.rs
@@ -211,6 +211,15 @@ pub struct PythonSignature {
     pub accepts_kwargs: bool,
 }
 
+impl PythonSignature {
+    pub fn has_no_args(&self) -> bool {
+        self.positional_parameters.is_empty()
+            && self.keyword_only_parameters.is_empty()
+            && !self.accepts_varargs
+            && !self.accepts_kwargs
+    }
+}
+
 pub struct FunctionSignature<'a> {
     pub arguments: Vec<FnArg<'a>>,
     pub python_signature: PythonSignature,