Add support for PYO3_ENVIRONMENT_SIGNATURE

.config/nextest.toml

@@ -0,0 +1,3 @@
+[profile.default]
+# Terminate slow tests after 5 minutes
+slow-timeout = { period = "60s", terminate-after = 5 }

src/compile.rs

@@ -350,7 +350,12 @@ fn compile_target(
                 || (matches!(bindings_crate, BridgeModel::BindingsAbi3(_, _))
                     && interpreter.interpreter_kind.is_pypy())
             {
-                build_command.env("PYO3_PYTHON", &interpreter.executable);
+                build_command
+                    .env("PYO3_PYTHON", &interpreter.executable)
+                    .env(
+                        "PYO3_ENVIRONMENT_SIGNATURE",
+                        interpreter.environment_signature(),
+                    );
             }
 
             // rust-cpython, and legacy pyo3 versions

src/python_interpreter/mod.rs

@@ -846,6 +846,16 @@ impl PythonInterpreter {
             }
         }
     }
+
+    /// An opaque string that uniquely identifies this Python interpreter.
+    /// Used to trigger rebuilds for `pyo3` when the Python interpreter changes.
+    pub fn environment_signature(&self) -> String {
+        let pointer_width = self.pointer_width.unwrap_or(64);
+        format!(
+            "{}-{}.{}-{}bit",
+            self.implmentation_name, self.major, self.minor, pointer_width
+        )
+    }
 }
 
 impl fmt::Display for PythonInterpreter {

tests/run.rs

@@ -248,6 +248,7 @@ fn integration_pyo3_mixed_src_layout() {
 }
 
 #[test]
+#[cfg_attr(target_os = "macos", ignore)] // Don't run it on macOS, too slow
 fn integration_pyo3_pure_conda() {
     // Only run on GitHub Actions for now
     if std::env::var("GITHUB_ACTIONS").is_ok() {