implement `PyModuleMethods::filename` on PyPy (#4249)

newsfragments/4249.added.md

@@ -0,0 +1 @@
+Implement `PyModuleMethods::filename` on PyPy.

src/types/module.rs

@@ -220,7 +220,6 @@ impl PyModule {
     /// Returns the filename (the `__file__` attribute) of the module.
     ///
     /// May fail if the module does not have a `__file__` attribute.
-    #[cfg(not(PyPy))]
     pub fn filename(&self) -> PyResult<&str> {
         self.as_borrowed().filename()?.into_gil_ref().to_str()
     }
@@ -429,7 +428,6 @@ pub trait PyModuleMethods<'py>: crate::sealed::Sealed {
     /// Returns the filename (the `__file__` attribute) of the module.
     ///
     /// May fail if the module does not have a `__file__` attribute.
-    #[cfg(not(PyPy))]
     fn filename(&self) -> PyResult<Bound<'py, PyString>>;
 
     /// Adds an attribute to the module.
@@ -644,13 +642,22 @@ impl<'py> PyModuleMethods<'py> for Bound<'py, PyModule> {
         }
     }
 
-    #[cfg(not(PyPy))]
     fn filename(&self) -> PyResult<Bound<'py, PyString>> {
+        #[cfg(not(PyPy))]
         unsafe {
             ffi::PyModule_GetFilenameObject(self.as_ptr())
                 .assume_owned_or_err(self.py())
                 .downcast_into_unchecked()
         }
+
+        #[cfg(PyPy)]
+        {
+            self.dict()
+                .get_item("__file__")
+                .map_err(|_| exceptions::PyAttributeError::new_err("__file__"))?
+                .downcast_into()
+                .map_err(PyErr::from)
+        }
     }
 
     fn add<N, V>(&self, name: N, value: V) -> PyResult<()>
@@ -737,7 +744,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(PyPy))]
     fn module_filename() {
         Python::with_gil(|py| {
             let site = PyModule::import_bound(py, "site").unwrap();