generate individual deprecation messages per function

guide/src/function/signature.md

@@ -123,7 +123,7 @@ num=-1
 
 <div class="warning">
 
-⚠️ Warning: This behaviour is phased out 🛠️
+⚠️ Warning: This behaviour is being phased out 🛠️
 
 The special casing of trailing optional arguments is deprecated. In a future `pyo3` version, arguments of type `Option<..>` will share the same behaviour as other arguments, they are required unless a default is set using `#[pyo3(signature = (...))]`.
 

pyo3-macros-backend/src/deprecations.rs

@@ -1,4 +1,7 @@
-use crate::utils::Ctx;
+use crate::{
+    method::{FnArg, FnSpec},
+    utils::Ctx,
+};
 use proc_macro2::{Span, TokenStream};
 use quote::{quote_spanned, ToTokens};
 
@@ -45,3 +48,50 @@ impl<'ctx> ToTokens for Deprecations<'ctx> {
         }
     }
 }
+
+pub(crate) fn deprecate_trailing_option_default(spec: &FnSpec<'_>) -> TokenStream {
+    if spec.signature.attribute.is_none()
+        && spec.signature.arguments.iter().any(|arg| {
+            if let FnArg::Regular(arg) = arg {
+                arg.option_wrapped_type.is_some()
+            } else {
+                false
+            }
+        })
+    {
+        use std::fmt::Write;
+        let mut deprecation_msg = String::from(
+            "This function has implicit defaults for the trailing `Option<T>` arguments. \
+             These implicit defaults are being phased out. Add `#[pyo3(signature = (",
+        );
+        spec.signature.arguments.iter().for_each(|arg| {
+            match arg {
+                FnArg::Regular(arg) => {
+                    if arg.option_wrapped_type.is_some() {
+                        write!(deprecation_msg, "{}=None, ", arg.name)
+                    } else {
+                        write!(deprecation_msg, "{}, ", arg.name)
+                    }
+                }
+                FnArg::VarArgs(arg) => write!(deprecation_msg, "{}, ", arg.name),
+                FnArg::KwArgs(arg) => write!(deprecation_msg, "{}, ", arg.name),
+                FnArg::Py(_) | FnArg::CancelHandle(_) => Ok(()),
+            }
+            .expect("writing to `String` should not fail");
+        });
+
+        //remove trailing space and comma
+        deprecation_msg.pop();
+        deprecation_msg.pop();
+
+        deprecation_msg
+            .push_str(")]` to this function to silence this warning and keep the current behavior");
+        quote_spanned! { spec.name.span() =>
+            #[deprecated(note = #deprecation_msg)]
+            const SIGNATURE: () = ();
+            const _: () = SIGNATURE;
+        }
+    } else {
+        TokenStream::new()
+    }
+}

pyo3-macros-backend/src/method.rs

@@ -5,6 +5,7 @@ use proc_macro2::{Span, TokenStream};
 use quote::{format_ident, quote, quote_spanned, ToTokens};
 use syn::{ext::IdentExt, spanned::Spanned, Ident, Result};
 
+use crate::deprecations::deprecate_trailing_option_default;
 use crate::utils::Ctx;
 use crate::{
     attributes::{FromPyWithAttribute, TextSignatureAttribute, TextSignatureAttributeValue},
@@ -708,6 +709,8 @@ impl<'a> FnSpec<'a> {
             quote!(#func_name)
         };
 
+        let deprecation = deprecate_trailing_option_default(self);
+
         Ok(match self.convention {
             CallingConvention::Noargs => {
                 let mut holders = Holders::new();
@@ -730,6 +733,7 @@ impl<'a> FnSpec<'a> {
                         py: #pyo3_path::Python<'py>,
                         _slf: *mut #pyo3_path::ffi::PyObject,
                     ) -> #pyo3_path::PyResult<*mut #pyo3_path::ffi::PyObject> {
+                        #deprecation
                         let _slf_ref = &_slf;
                         let function = #rust_name; // Shadow the function name to avoid #3017
                         #init_holders
@@ -754,6 +758,7 @@ impl<'a> FnSpec<'a> {
                         _nargs: #pyo3_path::ffi::Py_ssize_t,
                         _kwnames: *mut #pyo3_path::ffi::PyObject
                     ) -> #pyo3_path::PyResult<*mut #pyo3_path::ffi::PyObject> {
+                        #deprecation
                         let _slf_ref = &_slf;
                         let function = #rust_name; // Shadow the function name to avoid #3017
                         #arg_convert
@@ -778,6 +783,7 @@ impl<'a> FnSpec<'a> {
                         _args: *mut #pyo3_path::ffi::PyObject,
                         _kwargs: *mut #pyo3_path::ffi::PyObject
                     ) -> #pyo3_path::PyResult<*mut #pyo3_path::ffi::PyObject> {
+                        #deprecation
                         let _slf_ref = &_slf;
                         let function = #rust_name; // Shadow the function name to avoid #3017
                         #arg_convert
@@ -805,6 +811,7 @@ impl<'a> FnSpec<'a> {
                         _kwargs: *mut #pyo3_path::ffi::PyObject
                     ) -> #pyo3_path::PyResult<*mut #pyo3_path::ffi::PyObject> {
                         use #pyo3_path::callback::IntoPyCallbackOutput;
+                        #deprecation
                         let _slf_ref = &_slf;
                         let function = #rust_name; // Shadow the function name to avoid #3017
                         #arg_convert

pyo3-macros-backend/src/params.rs

@@ -134,16 +134,7 @@ pub fn impl_arg_params(
             .arguments
             .iter()
             .enumerate()
-            .map(|(i, arg)| {
-                impl_arg_param(
-                    arg,
-                    spec.signature.attribute.is_some(),
-                    i,
-                    &mut 0,
-                    holders,
-                    ctx,
-                )
-            })
+            .map(|(i, arg)| impl_arg_param(arg, i, &mut 0, holders, ctx))
             .collect();
         return (
             quote! {
@@ -183,16 +174,7 @@ pub fn impl_arg_params(
         .arguments
         .iter()
         .enumerate()
-        .map(|(i, arg)| {
-            impl_arg_param(
-                arg,
-                spec.signature.attribute.is_some(),
-                i,
-                &mut option_pos,
-                holders,
-                ctx,
-            )
-        })
+        .map(|(i, arg)| impl_arg_param(arg, i, &mut option_pos, holders, ctx))
         .collect();
 
     let args_handler = if spec.signature.python_signature.varargs.is_some() {
@@ -255,7 +237,6 @@ pub fn impl_arg_params(
 
 fn impl_arg_param(
     arg: &FnArg<'_>,
-    has_signature_attr: bool,
     pos: usize,
     option_pos: &mut usize,
     holders: &mut Holders,
@@ -269,14 +250,7 @@ fn impl_arg_param(
             let from_py_with = format_ident!("from_py_with_{}", pos);
             let arg_value = quote!(#args_array[#option_pos].as_deref());
             *option_pos += 1;
-            let tokens = impl_regular_arg_param(
-                arg,
-                has_signature_attr,
-                from_py_with,
-                arg_value,
-                holders,
-                ctx,
-            );
+            let tokens = impl_regular_arg_param(arg, from_py_with, arg_value, holders, ctx);
             check_arg_for_gil_refs(tokens, holders.push_gil_refs_checker(arg.ty.span()), ctx)
         }
         FnArg::VarArgs(arg) => {
@@ -311,7 +285,6 @@ fn impl_arg_param(
 /// index and the index in option diverge when using py: Python
 pub(crate) fn impl_regular_arg_param(
     arg: &RegularArg<'_>,
-    has_signature_attr: bool,
     from_py_with: syn::Ident,
     arg_value: TokenStream, // expected type: Option<&'a Bound<'py, PyAny>>
     holders: &mut Holders,
@@ -362,11 +335,6 @@ pub(crate) fn impl_regular_arg_param(
         }
     } else if arg.option_wrapped_type.is_some() {
         let holder = holders.push_holder(arg.name.span());
-        let arg_value = if !has_signature_attr {
-            quote_arg_span! { #pyo3_path::impl_::deprecations::deprecate_implicit_option(#arg_value) }
-        } else {
-            quote!(#arg_value)
-        };
         quote_arg_span! {
             #pyo3_path::impl_::extract_argument::extract_optional_argument(
                 #arg_value,

pyo3-macros-backend/src/pymethod.rs

@@ -1,6 +1,7 @@
 use std::borrow::Cow;
 
 use crate::attributes::{NameAttribute, RenamingRule};
+use crate::deprecations::deprecate_trailing_option_default;
 use crate::method::{CallingConvention, ExtractErrorMode, PyArg};
 use crate::params::{check_arg_for_gil_refs, impl_regular_arg_param, Holders};
 use crate::utils::Ctx;
@@ -630,15 +631,17 @@ pub fn impl_py_setter_def(
 
             let tokens = impl_regular_arg_param(
                 arg,
-                spec.signature.attribute.is_some(),
                 ident,
                 quote!(::std::option::Option::Some(_value.into())),
                 &mut holders,
                 ctx,
             );
             let extract =
                 check_arg_for_gil_refs(tokens, holders.push_gil_refs_checker(arg.ty.span()), ctx);
+
+            let deprecation = deprecate_trailing_option_default(spec);
             quote! {
+                #deprecation
                 #from_py_with
                 let _val = #extract;
             }

src/impl_/deprecations.rs

@@ -85,13 +85,3 @@ impl<T> std::ops::Deref for OptionGilRefs<T> {
         &self.0
     }
 }
-
-#[deprecated(
-    since = "0.22.0",
-    note = "Implicit default for trailing optional arguments is phased out. Add an explicit \
-            `#[pyo3(signature = (...))]` attribute a to silence this warning. In a future \
-            pyo3 version `Option<..>` arguments will be treated the same as any other argument."
-)]
-pub fn deprecate_implicit_option<T>(t: T) -> T {
-    t
-}

tests/test_pyfunction.rs

@@ -182,6 +182,7 @@ fn test_from_py_with_defaults() {
 
     // issue 2280 combination of from_py_with and Option<T> did not compile
     #[pyfunction]
+    #[pyo3(signature = (int=None))]
     fn from_py_with_option(#[pyo3(from_py_with = "optional_int")] int: Option<i32>) -> i32 {
         int.unwrap_or(0)
     }

tests/ui/deprecations.rs

@@ -39,6 +39,9 @@ impl MyClass {
     #[setter]
     fn set_bar_bound(&self, _value: &Bound<'_, PyAny>) {}
 
+    #[setter]
+    fn set_option(&self, _value: Option<i32>) {}
+
     fn __eq__(&self, #[pyo3(from_py_with = "extract_gil_ref")] _other: i32) -> bool {
         true
     }
@@ -105,6 +108,10 @@ fn extract_bound(obj: &Bound<'_, PyAny>) -> PyResult<i32> {
     obj.extract()
 }
 
+fn extract_options(obj: &Bound<'_, PyAny>) -> PyResult<Option<i32>> {
+    obj.extract()
+}
+
 #[pyfunction]
 fn pyfunction_from_py_with(
     #[pyo3(from_py_with = "extract_gil_ref")] _gil_ref: i32,
@@ -126,6 +133,17 @@ fn pyfunction_option_1(_i: u32, _any: Option<i32>) {}
 #[pyfunction]
 fn pyfunction_option_2(_i: u32, _any: Option<i32>) {}
 
+#[pyfunction]
+fn pyfunction_option_3(_i: u32, _any: Option<i32>, _foo: Option<String>) {}
+
+#[pyfunction]
+fn pyfunction_option_4(
+    _i: u32,
+    #[pyo3(from_py_with = "extract_options")] _any: Option<i32>,
+    _foo: Option<String>,
+) {
+}
+
 #[derive(Debug, FromPyObject)]
 pub struct Zap {
     #[pyo3(item)]