PyO3 · davidhewitt · Jun 5, 2021 · Jun 5, 2021
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Add FFI definition `PyDateTime_TimeZone_UTC`. [#1572](https://github.com/PyO3/pyo3/pull/1572)
 - Add support for `#[pyclass(extends=Exception)]`. [#1591](https://github.com/PyO3/pyo3/pull/1591)
 - Add support for extracting `PathBuf` from `pathlib.Path`. [#1654](https://github.com/PyO3/pyo3/pull/1654)
+- Add `#[pyo3(text_signature = "...")]` syntax for setting text signature. [#1658](https://github.com/PyO3/pyo3/pull/1658)
 
 ### Changed
 - Allow only one `#[pymethods]` block per `#[pyclass]` by default, to simplify the proc macro implementations. Add `multiple-pymethods` feature to opt-in to the more complex full behavior. [#1457](https://github.com/PyO3/pyo3/pull/1457)
@@ -49,6 +50,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Deprecate string-literal second argument to `#[pyfn(m, "name")]`. [#1610](https://github.com/PyO3/pyo3/pull/1610)
 - No longer call `PyEval_InitThreads()` in `#[pymodule]` init code. [#1630](https://github.com/PyO3/pyo3/pull/1630)
 - Use `METH_FASTCALL` argument passing convention, when possible, to improve `#[pyfunction]` performance. [#1619](https://github.com/PyO3/pyo3/pull/1619)
+- Deprecate `#[text_signature = "..."]` attributes in favor of `#[pyo3(text_signature = "...")]`. [#1658](https://github.com/PyO3/pyo3/pull/1658)
 
 ### Removed
 - Remove deprecated exception names `BaseException` etc. [#1426](https://github.com/PyO3/pyo3/pull/1426)

diff --git a/guide/src/building_and_distribution.md b/guide/src/building_and_distribution.md
@@ -41,10 +41,10 @@ There are two main ways to test, build and distribute your module as a Python pa
 
 ### Manual builds
 
-You can also symlink (or copy) and rename the shared library from the `target` folder: 
+You can also symlink (or copy) and rename the shared library from the `target` folder:
 - on macOS, rename `libyour_module.dylib` to `your_module.so`.
 - on Windows, rename  `libyour_module.dll` to `your_module.pyd`.
-- on Linux, rename `libyour_module.so` to `your_module.so`. 
+- on Linux, rename `libyour_module.so` to `your_module.so`.
 
 You can then open a Python shell in the same folder and you'll be able to use `import your_module`.
 
@@ -86,7 +86,7 @@ As an advanced feature, you can build PyO3 wheel without calling Python interpre
 Due to limitations in the Python API, there are a few `pyo3` features that do
 not work when compiling for `abi3`. These are:
 
-- `#[text_signature]` does not work on classes until Python 3.10 or greater.
+- `#[pyo3(text_signature = "...")]` does not work on classes until Python 3.10 or greater.
 - The `dict` and `weakref` options on classes are not supported until Python 3.9 or greater.
 - The buffer API is not supported.
 - Optimizations which rely on knowledge of the exact Python version compiled against.

diff --git a/guide/src/function.md b/guide/src/function.md
@@ -117,7 +117,7 @@ fn module_with_functions(py: Python, m: &PyModule) -> PyResult<()> {
 ## Making the function signature available to Python
 
 In order to make the function signature available to Python to be retrieved via
-`inspect.signature`, use the `#[text_signature]` annotation as in the example
+`inspect.signature`, use the `#[pyo3(text_signature)]` annotation as in the example
 below. The `/` signifies the end of positional-only arguments. (This
 is not a feature of this library in particular, but the general format used by
 CPython for annotating signatures of built-in functions.)
@@ -127,7 +127,7 @@ use pyo3::prelude::*;
 
 /// This function adds two unsigned 64-bit integers.
 #[pyfunction]
-#[text_signature = "(a, b, /)"]
+#[pyo3(text_signature = "(a, b, /)")]
 fn add(a: u64, b: u64) -> u64 {
     a + b
 }
@@ -142,7 +142,7 @@ use pyo3::types::PyType;
 // it works even if the item is not documented:
 
 #[pyclass]
-#[text_signature = "(c, d, /)"]
+#[pyo3(text_signature = "(c, d, /)")]
 struct MyClass {}
 
 #[pymethods]
@@ -154,17 +154,17 @@ impl MyClass {
         Self {}
     }
     // the self argument should be written $self
-    #[text_signature = "($self, e, f)"]
+    #[pyo3(text_signature = "($self, e, f)")]
     fn my_method(&self, e: i32, f: i32) -> i32 {
         e + f
     }
     #[classmethod]
-    #[text_signature = "(cls, e, f)"]
+    #[pyo3(text_signature = "(cls, e, f)")]
     fn my_class_method(cls: &PyType, e: i32, f: i32) -> i32 {
         e + f
     }
     #[staticmethod]
-    #[text_signature = "(e, f)"]
+    #[pyo3(text_signature = "(e, f)")]
     fn my_static_method(e: i32, f: i32) -> i32 {
         e + f
     }
@@ -180,7 +180,7 @@ Alternatively, simply make sure the first line of your docstring is
 formatted like in the following example. Please note that the newline after the
 `--` is mandatory. The `/` signifies the end of positional-only arguments.
 
-`#[text_signature]` should be preferred, since it will override automatically
+`#[pyo3(text_signature)]` should be preferred, since it will override automatically
 generated signatures when those are added in a future version of PyO3.
 
 ```rust

diff --git a/pyo3-macros-backend/src/attributes.rs b/pyo3-macros-backend/src/attributes.rs
@@ -18,6 +18,7 @@ pub mod kw {
     syn::custom_keyword!(name);
     syn::custom_keyword!(set);
     syn::custom_keyword!(signature);
+    syn::custom_keyword!(text_signature);
     syn::custom_keyword!(transparent);
 }
 
@@ -45,6 +46,23 @@ impl Parse for NameAttribute {
     }
 }
 
+#[derive(Clone, Debug, PartialEq)]
+pub struct TextSignatureAttribute {
+    pub kw: kw::text_signature,
+    pub eq_token: Token![=],
+    pub lit: LitStr,
+}
+
+impl Parse for TextSignatureAttribute {
+    fn parse(input: ParseStream) -> Result<Self> {
+        Ok(TextSignatureAttribute {
+            kw: input.parse()?,
+            eq_token: input.parse()?,
+            lit: input.parse()?,
+        })
+    }
+}
+
 pub fn get_pyo3_options<T: Parse>(attr: &syn::Attribute) -> Result<Option<Punctuated<T, Comma>>> {
     if is_attribute_ident(attr, "pyo3") {
         attr.parse_args_with(Punctuated::parse_terminated).map(Some)
@@ -112,3 +130,49 @@ pub fn get_deprecated_name_attribute(
         _ => Ok(None),
     }
 }
+
+pub fn get_deprecated_text_signature_attribute(
+    attr: &syn::Attribute,
+    deprecations: &mut Deprecations,
+) -> syn::Result<Option<TextSignatureAttribute>> {
+    match attr.parse_meta() {
+        Ok(syn::Meta::NameValue(syn::MetaNameValue {
+            path,
+            lit: syn::Lit::Str(lit),
+            ..
+        })) if path.is_ident("text_signature") => {
+            let text_signature = TextSignatureAttribute {
+                kw: syn::parse_quote!(text_signature),
+                eq_token: syn::parse_quote!(=),
+                lit,
+            };
+            deprecations.push(
+                crate::deprecations::Deprecation::TextSignatureAttribute,
+                attr.span(),
+            );
+            Ok(Some(text_signature))
+        }
+        _ => Ok(None),
+    }
+}
+
+pub fn take_deprecated_text_signature_attribute(
+    attrs: &mut Vec<syn::Attribute>,
+    deprecations: &mut Deprecations,
+) -> syn::Result<Option<TextSignatureAttribute>> {
+    let mut text_signature = None;
+    let mut attrs_out = Vec::with_capacity(attrs.len());
+    for attr in attrs.drain(..) {
+        if let Some(value) = get_deprecated_text_signature_attribute(&attr, deprecations)? {
+            ensure_spanned!(
+                text_signature.is_none(),
+                attr.span() => "text_signature attribute already specified previously"
+            );
+            text_signature = Some(value);
+        } else {
+            attrs_out.push(attr);
+        }
+    }
+    *attrs = attrs_out;
+    Ok(text_signature)
+}
diff --git a/pyo3-macros-backend/src/deprecations.rs b/pyo3-macros-backend/src/deprecations.rs
@@ -4,13 +4,15 @@ use quote::{quote_spanned, ToTokens};
 pub enum Deprecation {
     NameAttribute,
     PyfnNameArgument,
+    TextSignatureAttribute,
 }
 
 impl Deprecation {
     fn ident(&self, span: Span) -> syn::Ident {
         let string = match self {
             Deprecation::NameAttribute => "NAME_ATTRIBUTE",
             Deprecation::PyfnNameArgument => "PYFN_NAME_ARGUMENT",
+            Deprecation::TextSignatureAttribute => "TEXT_SIGNATURE_ATTRIBUTE",
         };
         syn::Ident::new(string, span)
     }

diff --git a/pyo3-macros-backend/src/method.rs b/pyo3-macros-backend/src/method.rs
@@ -1,5 +1,6 @@
 // Copyright (c) 2017-present PyO3 Project and Contributors
 
+use crate::attributes::TextSignatureAttribute;
 use crate::pyfunction::PyFunctionOptions;
 use crate::pyfunction::{PyFunctionArgPyO3Attributes, PyFunctionSignature};
 use crate::utils;
@@ -209,13 +210,19 @@ impl<'a> FnSpec<'a> {
         }
 
         let (fn_type, skip_first_arg) = Self::parse_fn_type(sig, fn_type_attr, &mut python_name)?;
+        Self::ensure_text_signature_on_valid_method(&fn_type, options.text_signature.as_ref())?;
 
         let name = &sig.ident;
         let ty = get_return_info(&sig.output);
         let python_name = python_name.as_ref().unwrap_or(name).unraw();
 
-        let text_signature = Self::parse_text_signature(meth_attrs, &fn_type, &python_name)?;
-        let doc = utils::get_doc(&meth_attrs, text_signature, true)?;
+        let doc = utils::get_doc(
+            &meth_attrs,
+            options
+                .text_signature
+                .as_ref()
+                .map(|attr| (&python_name, attr)),
+        )?;
 
         let arguments = if skip_first_arg {
             sig.inputs
@@ -246,36 +253,27 @@ impl<'a> FnSpec<'a> {
         syn::LitStr::new(&format!("{}\0", self.python_name), self.python_name.span())
     }
 
-    fn parse_text_signature(
-        meth_attrs: &mut Vec<syn::Attribute>,
+    fn ensure_text_signature_on_valid_method(
         fn_type: &FnType,
-        python_name: &syn::Ident,
-    ) -> syn::Result<Option<syn::LitStr>> {
-        let mut parse_erroneous_text_signature = |error_msg: &str| {
-            // try to parse anyway to give better error messages
-            if let Some(text_signature) =
-                utils::parse_text_signature_attrs(meth_attrs, &python_name)?
-            {
-                bail_spanned!(text_signature.span() => error_msg)
-            } else {
-                Ok(None)
-            }
-        };
-
-        let text_signature = match &fn_type {
-            FnType::Fn(_) | FnType::FnClass | FnType::FnStatic => {
-                utils::parse_text_signature_attrs(&mut *meth_attrs, &python_name)?
+        text_signature: Option<&TextSignatureAttribute>,
+    ) -> syn::Result<()> {
+        if let Some(text_signature) = text_signature {
+            match &fn_type {
+                FnType::FnNew => bail_spanned!(
+                    text_signature.kw.span() =>
+                    "text_signature not allowed on __new__; if you want to add a signature on \
+                     __new__, put it on the struct definition instead"
+                ),
+                FnType::FnCall(_)
+                | FnType::Getter(_)
+                | FnType::Setter(_)
+                | FnType::ClassAttribute => bail_spanned!(
+                    text_signature.kw.span() => "text_signature not allowed with this method type"
+                ),
+                _ => {}
             }
-            FnType::FnNew => parse_erroneous_text_signature(
-                "text_signature not allowed on __new__; if you want to add a signature on \
-                 __new__, put it on the struct definition instead",
-            )?,
-            FnType::FnCall(_) | FnType::Getter(_) | FnType::Setter(_) | FnType::ClassAttribute => {
-                parse_erroneous_text_signature("text_signature not allowed with this method type")?
-            }
-        };
-
-        Ok(text_signature)
+        }
+        Ok(())
     }
 
     fn parse_fn_type(

diff --git a/pyo3-macros-backend/src/module.rs b/pyo3-macros-backend/src/module.rs
@@ -14,6 +14,7 @@ use syn::{parse::Parse, spanned::Spanned, token::Comma, Ident, Path};
 /// module
 pub fn py_init(fnname: &Ident, name: &Ident, doc: syn::LitStr) -> TokenStream {
     let cb_name = Ident::new(&format!("PyInit_{}", name), Span::call_site());
+    assert!(doc.value().ends_with('\0'));
 
     quote! {
         #[no_mangle]
@@ -23,7 +24,7 @@ pub fn py_init(fnname: &Ident, name: &Ident, doc: syn::LitStr) -> TokenStream {
         pub unsafe extern "C" fn #cb_name() -> *mut pyo3::ffi::PyObject {
             use pyo3::derive_utils::ModuleDef;
             static NAME: &str = concat!(stringify!(#name), "\0");
-            static DOC: &str = concat!(#doc, "\0");
+            static DOC: &str = #doc;
             static MODULE_DEF: ModuleDef = unsafe { ModuleDef::new(NAME, DOC) };
 
             pyo3::callback::handle_panic(|_py| { MODULE_DEF.make_module(_py, #fnname) })