From d5509424b22b25bd64b6cb66fbb9b573d3a17901 Mon Sep 17 00:00:00 2001
From: David Hewitt <1939362+davidhewitt@users.noreply.github.com>
Date: Sat, 15 Feb 2020 14:05:12 +0000
Subject: [PATCH] Make #[pymethods] aware of #[cfg]

---
 CHANGELOG.md                      |  1 +
 pyo3-derive-backend/src/pyimpl.rs | 15 +++++++--
 tests/test_methods.rs             | 51 +++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9722cd2dcdf..6929e41acda 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * Clear error indicator when the exception is handled on the Rust side. [#719](https://github.com/PyO3/pyo3/pull/719)
 * Usage of raw identifiers with `#[pyo3(set)]`. [#745](https://github.com/PyO3/pyo3/pull/745)
 * Usage of `PyObject` with `#[pyo3(get)]`. [#760](https://github.com/PyO3/pyo3/pull/760)
+* `#[pymethods]` used in conjunction with `#[cfg]`. #[769](https://github.com/PyO3/pyo3/pull/769)
 
 ### Removed
 
diff --git a/pyo3-derive-backend/src/pyimpl.rs b/pyo3-derive-backend/src/pyimpl.rs
index 89e09c532db..e62df4f338a 100644
--- a/pyo3-derive-backend/src/pyimpl.rs
+++ b/pyo3-derive-backend/src/pyimpl.rs
@@ -21,11 +21,12 @@ pub fn build_py_methods(ast: &mut syn::ItemImpl) -> syn::Result<TokenStream> {
 }
 
 pub fn impl_methods(ty: &syn::Type, impls: &mut Vec<syn::ImplItem>) -> syn::Result<TokenStream> {
-    // get method names in impl block
     let mut methods = Vec::new();
+    let mut cfg_attributes = Vec::new();
     for iimpl in impls.iter_mut() {
         if let syn::ImplItem::Method(ref mut meth) = iimpl {
             methods.push(pymethod::gen_py_method(ty, &mut meth.sig, &mut meth.attrs)?);
+            cfg_attributes.push(get_cfg_attributes(&meth.attrs));
         }
     }
 
@@ -33,8 +34,18 @@ pub fn impl_methods(ty: &syn::Type, impls: &mut Vec<syn::ImplItem>) -> syn::Resu
        pyo3::inventory::submit! {
             #![crate = pyo3] {
                 type TyInventory = <#ty as pyo3::class::methods::PyMethodsInventoryDispatch>::InventoryType;
-                <TyInventory as pyo3::class::methods::PyMethodsInventory>::new(&[#(#methods),*])
+                <TyInventory as pyo3::class::methods::PyMethodsInventory>::new(&[#(
+                    #(#cfg_attributes)*
+                    #methods
+                ),*])
             }
         }
     })
 }
+
+fn get_cfg_attributes(attrs: &[syn::Attribute]) -> Vec<&syn::Attribute> {
+    attrs
+        .iter()
+        .filter(|attr| attr.path.is_ident("cfg"))
+        .collect()
+}
diff --git a/tests/test_methods.rs b/tests/test_methods.rs
index 153bc2b5fca..a23942da259 100644
--- a/tests/test_methods.rs
+++ b/tests/test_methods.rs
@@ -402,3 +402,54 @@ fn method_with_lifetime() {
         "assert obj.set_to_list(set((1, 2, 3))) == [1, 2, 3]"
     );
 }
+
+#[pyclass]
+#[cfg(unix)]
+struct CfgStruct {}
+
+#[pyclass]
+#[cfg(not(unix))]
+struct CfgStruct {}
+
+#[pymethods]
+#[cfg(unix)]
+impl CfgStruct {
+    fn unix_method(&self) -> &str {
+        "unix"
+    }
+
+    #[cfg(not(unix))]
+    fn never_compiled_method(&self) {}
+}
+
+#[pymethods]
+#[cfg(not(unix))]
+impl CfgStruct {
+    fn not_unix_method(&self) -> &str {
+        "not unix"
+    }
+
+    #[cfg(unix)]
+    fn never_compiled_method(&self) {}
+}
+
+#[test]
+fn test_cfg_attrs() {
+    let gil = Python::acquire_gil();
+    let py = gil.python();
+    let inst = Py::new(py, CfgStruct {}).unwrap();
+
+    #[cfg(unix)]
+    {
+        py_assert!(py, inst, "inst.unix_method() == 'unix'");
+        py_assert!(py, inst, "not hasattr(inst, 'not_unix_method')");
+    }
+
+    #[cfg(not(unix))]
+    {
+        py_assert!(py, inst, "not hasattr(inst, 'unix_method')");
+        py_assert!(py, inst, "inst.not_unix_method() == 'not unix'");
+    }
+
+    py_assert!(py, inst, "not hasattr(inst, 'never_compiled_method')");
+}