RFC: Simplify version handling of UI tests.

.github/workflows/build.yml

@@ -59,6 +59,10 @@ jobs:
         name: Prepare minimal package versions (MSRV only)
         run: nox -s set-minimal-package-versions
 
+      - if: inputs.rust == 'nightly' || inputs.msrv == 'MSRV'
+        name: Ignore changed error messages when using trybuild
+        run: echo "TRYBUILD=overwrite" >> "$GITHUB_ENV"
+
       - name: Build docs
         run: cargo doc --no-deps --no-default-features --features "full ${{ inputs.extra-features }}"
 

Cargo.toml

@@ -10,7 +10,7 @@ repository = "https://github.com/pyo3/pyo3"
 documentation = "https://docs.rs/crate/pyo3/"
 categories = ["api-bindings", "development-tools::ffi"]
 license = "Apache-2.0"
-exclude = ["/.gitignore", ".cargo/config", "/codecov.yml", "/Makefile", "/pyproject.toml", "/noxfile.py"]
+exclude = ["/.gitignore", ".cargo/config", "/codecov.yml", "/Makefile", "/pyproject.toml", "/noxfile.py", "/.github", "/tests/test_compile_error.rs", "/tests/ui"]
 edition = "2018"
 
 [dependencies]

src/marker.rs

@@ -140,6 +140,48 @@ use std::os::raw::c_int;
 /// the GIL is not held.
 ///
 /// See the [module-level documentation](self) for more information.
+///
+/// # Examples
+///
+/// This tracking is currently imprecise as it relies on the [`Send`] auto trait on stable Rust.
+/// For example, an `Rc` smart pointer should be usable without the GIL, but we currently prevent that:
+///
+/// ```compile_fail
+/// # use pyo3::prelude::*;
+/// use std::rc::Rc;
+///
+/// Python::with_gil(|py| {
+///     let rc = Rc::new(42);
+///
+///     py.allow_threads(|| {
+///         println!("{:?}", rc);
+///     });
+/// });
+/// ```
+///
+/// This also implies that the interplay between `with_gil` and `allow_threads` is unsound, for example
+/// one can circumvent this protection using the [`send_wrapper`](https://docs.rs/send_wrapper/) crate:
+///
+/// ```no_run
+/// # use pyo3::prelude::*;
+/// # use pyo3::types::PyString;
+/// use send_wrapper::SendWrapper;
+///
+/// Python::with_gil(|py| {
+///     let string = PyString::new(py, "foo");
+///
+///     let wrapped = SendWrapper::new(string);
+///
+///     py.allow_threads(|| {
+///         let sneaky: &PyString = *wrapped;
+///
+///         println!("{:?}", sneaky);
+///     });
+/// });
+/// ```
+///
+/// Fixing this loophole on stable Rust has significant ergonomic issues, but it is fixed when using
+/// nightly Rust and the `nightly` feature, c.f. [#2141](https://github.com/PyO3/pyo3/issues/2141).
 #[cfg_attr(docsrs, doc(cfg(all())))] // Hide the cfg flag
 #[cfg(not(feature = "nightly"))]
 pub unsafe trait Ungil {}
@@ -156,6 +198,70 @@ unsafe impl<T: Send> Ungil for T {}
 /// the GIL is not held.
 ///
 /// See the [module-level documentation](self) for more information.
+///
+/// # Examples
+///
+/// Types which are `Ungil` cannot be used in contexts where the GIL was released, e.g.
+///
+/// ```compile_fail
+/// # use pyo3::prelude::*;
+/// # use pyo3::types::PyString;
+/// Python::with_gil(|py| {
+///     let string = PyString::new(py, "foo");
+///
+///     py.allow_threads(|| {
+///         println!("{:?}", string);
+///     });
+/// });
+/// ```
+///
+/// This applies to the GIL token `Python` itself as well, e.g.
+///
+/// ```compile_fail
+/// # use pyo3::prelude::*;
+/// Python::with_gil(|py| {
+///     py.allow_threads(|| {
+///         drop(py);
+///     });
+/// });
+/// ```
+///
+/// On nightly Rust, this is not based on the [`Send`] auto trait and hence we are able
+/// to prevent incorrectly circumventing it using e.g. the [`send_wrapper`](https://docs.rs/send_wrapper/) crate:
+///
+/// ```compile_fail
+/// # use pyo3::prelude::*;
+/// # use pyo3::types::PyString;
+/// use send_wrapper::SendWrapper;
+///
+/// Python::with_gil(|py| {
+///     let string = PyString::new(py, "foo");
+///
+///     let wrapped = SendWrapper::new(string);
+///
+///     py.allow_threads(|| {
+///         let sneaky: &PyString = *wrapped;
+///
+///         println!("{:?}", sneaky);
+///     });
+/// });
+/// ```
+///
+/// This also enables using non-[`Send`] types in `allow_threads`,
+/// at least if they are not also bound to the GIL:
+///
+/// ```rust
+/// # use pyo3::prelude::*;
+/// use std::rc::Rc;
+///
+/// Python::with_gil(|py| {
+///     let rc = Rc::new(42);
+///
+///     py.allow_threads(|| {
+///         println!("{:?}", rc);
+///     });
+/// });
+/// ```
 #[cfg(feature = "nightly")]
 pub unsafe auto trait Ungil {}
 

tests/test_compile_error.rs

@@ -1,35 +1,8 @@
 #![cfg(feature = "macros")]
 
-#[rustversion::not(nightly)]
 #[cfg(not(target_arch = "wasm32"))] // Not possible to invoke compiler from wasm
 #[test]
 fn test_compile_errors() {
-    // stable - require all tests to pass
-    _test_compile_errors()
-}
-
-#[cfg(not(feature = "nightly"))]
-#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
-#[rustversion::nightly]
-#[test]
-fn test_compile_errors() {
-    // nightly - don't care if test output is potentially wrong, to avoid churn in PyO3's CI thanks
-    // to diagnostics changing on nightly.
-    let _ = std::panic::catch_unwind(_test_compile_errors);
-}
-
-#[cfg(feature = "nightly")]
-#[cfg(not(target_arch = "wasm32"))] // Not possible to invoke compiler from wasm
-#[rustversion::nightly]
-#[test]
-fn test_compile_errors() {
-    // nightly - don't care if test output is potentially wrong, to avoid churn in PyO3's CI thanks
-    // to diagnostics changing on nightly.
-    _test_compile_errors()
-}
-
-#[cfg(not(feature = "nightly"))]
-fn _test_compile_errors() {
     let t = trybuild::TestCases::new();
 
     t.compile_fail("tests/ui/invalid_macro_args.rs");
@@ -45,91 +18,24 @@ fn _test_compile_errors() {
     t.compile_fail("tests/ui/invalid_pymethod_names.rs");
     t.compile_fail("tests/ui/invalid_pymodule_args.rs");
     t.compile_fail("tests/ui/reject_generics.rs");
-
-    tests_rust_1_49(&t);
-    tests_rust_1_56(&t);
-    tests_rust_1_57(&t);
-    tests_rust_1_58(&t);
-    tests_rust_1_60(&t);
-    tests_rust_1_62(&t);
-    tests_rust_1_63(&t);
-
-    #[rustversion::since(1.49)]
-    fn tests_rust_1_49(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/deprecations.rs");
-    }
-    #[rustversion::before(1.49)]
-    fn tests_rust_1_49(_t: &trybuild::TestCases) {}
-
-    #[rustversion::since(1.56)]
-    fn tests_rust_1_56(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/invalid_closure.rs");
-
-        t.compile_fail("tests/ui/pyclass_send.rs");
-    }
-
-    #[rustversion::before(1.56)]
-    fn tests_rust_1_56(_t: &trybuild::TestCases) {}
-
-    #[rustversion::since(1.57)]
-    fn tests_rust_1_57(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/invalid_argument_attributes.rs");
-        t.compile_fail("tests/ui/invalid_frompy_derive.rs");
-        t.compile_fail("tests/ui/static_ref.rs");
-        t.compile_fail("tests/ui/wrong_aspyref_lifetimes.rs");
-    }
-
-    #[rustversion::before(1.57)]
-    fn tests_rust_1_57(_t: &trybuild::TestCases) {}
-
-    #[rustversion::since(1.58)]
-    fn tests_rust_1_58(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/invalid_pyfunctions.rs");
-        t.compile_fail("tests/ui/invalid_pymethods.rs");
-        #[cfg(Py_LIMITED_API)]
-        t.compile_fail("tests/ui/abi3_nativetype_inheritance.rs");
-    }
-
-    #[rustversion::before(1.58)]
-    fn tests_rust_1_58(_t: &trybuild::TestCases) {}
-
-    #[rustversion::since(1.60)]
-    fn tests_rust_1_60(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/invalid_intern_arg.rs");
-        t.compile_fail("tests/ui/invalid_frozen_pyclass_borrow.rs");
-    }
-
-    #[rustversion::before(1.60)]
-    fn tests_rust_1_60(_t: &trybuild::TestCases) {}
-
-    #[rustversion::since(1.62)]
-    fn tests_rust_1_62(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/invalid_pymethod_receiver.rs");
-        t.compile_fail("tests/ui/missing_intopy.rs");
-    }
-
-    #[rustversion::before(1.62)]
-    fn tests_rust_1_62(_t: &trybuild::TestCases) {}
-
-    #[rustversion::since(1.63)]
-    fn tests_rust_1_63(t: &trybuild::TestCases) {
-        t.compile_fail("tests/ui/invalid_result_conversion.rs");
-        t.compile_fail("tests/ui/not_send.rs");
-        t.compile_fail("tests/ui/not_send2.rs");
-        t.compile_fail("tests/ui/not_send3.rs");
-        t.compile_fail("tests/ui/get_set_all.rs");
-        t.compile_fail("tests/ui/traverse_bare_self.rs");
-    }
-
-    #[rustversion::before(1.63)]
-    fn tests_rust_1_63(_t: &trybuild::TestCases) {}
-}
-
-#[cfg(feature = "nightly")]
-fn _test_compile_errors() {
-    let t = trybuild::TestCases::new();
-
-    t.compile_fail("tests/ui/not_send_auto_trait.rs");
-    t.compile_fail("tests/ui/not_send_auto_trait2.rs");
-    t.compile_fail("tests/ui/send_wrapper.rs");
+    t.compile_fail("tests/ui/deprecations.rs");
+    t.compile_fail("tests/ui/invalid_closure.rs");
+    t.compile_fail("tests/ui/pyclass_send.rs");
+    t.compile_fail("tests/ui/invalid_argument_attributes.rs");
+    t.compile_fail("tests/ui/invalid_frompy_derive.rs");
+    t.compile_fail("tests/ui/static_ref.rs");
+    t.compile_fail("tests/ui/wrong_aspyref_lifetimes.rs");
+    t.compile_fail("tests/ui/invalid_pyfunctions.rs");
+    t.compile_fail("tests/ui/invalid_pymethods.rs");
+    #[cfg(Py_LIMITED_API)]
+    t.compile_fail("tests/ui/abi3_nativetype_inheritance.rs");
+    t.compile_fail("tests/ui/invalid_intern_arg.rs");
+    t.compile_fail("tests/ui/invalid_frozen_pyclass_borrow.rs");
+    t.compile_fail("tests/ui/invalid_pymethod_receiver.rs");
+    t.compile_fail("tests/ui/missing_intopy.rs");
+    t.compile_fail("tests/ui/invalid_result_conversion.rs");
+    t.compile_fail("tests/ui/not_send.rs");
+    t.compile_fail("tests/ui/not_send2.rs");
+    t.compile_fail("tests/ui/get_set_all.rs");
+    t.compile_fail("tests/ui/traverse_bare_self.rs");
 }