add option to import modules into the main interpreter

- some modules crash the subinterpreters if this doesn't happen
- add pytest as a default (as it is required for it)
- re-enable the pytest mark tests

src/config.rs

@@ -19,6 +19,18 @@ pub(crate) struct Settings {
   #[clap(long, default_value_t = false)]
   pub no_fail_fast: bool,
 
+  /// List of (comma separated) modules to try to import in the main interpreter.
+  ///
+  /// Some modules need imported in the main interpreter, else they crash the subinterpreters.
+  #[clap(
+    long,
+    value_name = "MODULE_NAME",
+    num_args = 1..,
+    value_delimiter = ',',
+    default_value = "pytest",
+  )]
+  pub known_imports: Vec<String>,
+
   /// How test results should be reported
   #[clap(long, value_enum, default_value_t = OutputFormat::Standard)]
   pub output: OutputFormat,

src/main.rs

@@ -31,7 +31,11 @@ fn main() -> ExitCode {
   interpreter.with_gil(|python| {
     // The decimal module crashes Python 3.12 if it is initialised multiple times
     // If not initialised in the base interpreter, if a subinterpreter imports it it will crash
-    _ = python.import_module(c"decimal");
+    _ = python.import_known_module(c"decimal");
+
+    for module in &settings.known_imports {
+      _ = python.import_module(module);
+    }
   });
 
   // Run tests

src/python/objects.rs

@@ -2,6 +2,7 @@ use pyo3_ffi::{self as ffi};
 use std::{ffi::CStr, fmt, marker::PhantomData, ops::Deref, ptr::NonNull};
 
 /// Represents a Python object
+#[must_use]
 pub struct PyObject(NonNull<ffi::PyObject>);
 impl PyObject {
   /// Gets the underlying pointer for the object

src/python/operations.rs

@@ -27,10 +27,10 @@ impl ActiveInterpreter {
     unsafe { PyObject::from_ptr_unchecked(result) }
   }
 
-  /// Imports a module
+  /// Imports a known module
   ///
   /// SAFETY: Assumes that the module exists
-  pub fn import_module(&self, module: &CStr) -> PyObject {
+  pub fn import_known_module(&self, module: &CStr) -> PyObject {
     let result = unsafe { ffi::PyImport_ImportModule(module.as_ptr().cast()) };
 
     debug_assert!(!result.is_null());
@@ -40,12 +40,23 @@ impl ActiveInterpreter {
     object
   }
 
+  /// Imports a module which may not exist
+  #[must_use]
+  pub fn import_module(&self, module: &str) -> Option<PyObject> {
+    let module = self.new_string(module);
+    let result = unsafe { ffi::PyImport_Import(module.as_ptr()) };
+    if result.is_null() {
+      PyError::clear();
+    }
+    PyObject::from_ptr(result)
+  }
+
   /// Redirect stdout and stderr from Python into a string
   ///
   /// Captured output can be fetched by [`Self::get_captured_output`]
   pub fn capture_output(&self) {
-    let sys = self.import_module(c"sys");
-    let io = self.import_module(c"io");
+    let sys = self.import_known_module(c"sys");
+    let io = self.import_known_module(c"io");
 
     let string_io = io.get_attr(&self.new_string("StringIO")).unwrap();
     let stdout_io = unsafe { string_io.call_unchecked() };
@@ -57,7 +68,7 @@ impl ActiveInterpreter {
 
   /// Get the captured stdout and stderr
   pub fn get_captured_output(&self) -> (Option<String>, Option<String>) {
-    let sys = self.import_module(c"sys");
+    let sys = self.import_known_module(c"sys");
 
     let stdout = sys.get_attr(&self.new_string("stdout")).unwrap();
     let stderr = sys.get_attr(&self.new_string("stderr")).unwrap();
@@ -84,7 +95,7 @@ impl ActiveInterpreter {
   /// Most commonly used to add the current folder to the module search path.
   /// Assumes Python Interpreter is currently active.
   pub fn add_to_sys_modules_path(&self, path: &CStr) {
-    let sys = self.import_module(c"sys");
+    let sys = self.import_known_module(c"sys");
     let path_list = sys.get_attr(&self.new_string("path")).unwrap();
 
     unsafe {

tests/execution.rs

@@ -175,6 +175,7 @@ execution_test!(invalid_remove);
 execution_test!(isolated);
 #[cfg(feature = "ci")] // Takes a long time, so don't want it slowing down developement cycles
 execution_test!(long_running);
+execution_test!(pytest_marks);
 execution_test!(setup_teardown);
 execution_test!(skip_tests);
 execution_test!(times); // No tests are in this file, just a standard python file

tests/requirements.txt

@@ -1,3 +1,6 @@
-# Requirements for ./execution/dependencies.txt
+# Requirements for ./execution/dependencies.py
 astroid
 yarl
+
+# Requirements for ./execution/pytest_marks.py
+pytest