Set SourceFileLoader for script execution in run_simple_file (#6496)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

Lib/test/test_cmd_line_script.py

@@ -225,8 +225,6 @@ class CmdLineTest(unittest.TestCase):
     def test_repl_stderr_flush_separate_stderr(self):
         self.check_repl_stderr_flush(True)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_basic_script(self):
         with os_helper.temp_dir() as script_dir:
             script_name = _make_test_script(script_dir, 'script')

crates/vm/src/vm/compile.rs

@@ -81,7 +81,7 @@ impl VirtualMachine {
             todo!("running pyc is not implemented yet");
         } else {
             if path != "<stdin>" {
-                // TODO: set_main_loader(dict, filename, "SourceFileLoader");
+                set_main_loader(&module_dict, path, self)?;
             }
             // TODO: replace to something equivalent to py_run_file
             match std::fs::read_to_string(path) {
@@ -125,6 +125,16 @@ impl VirtualMachine {
     }
 }
 
+fn set_main_loader(module_dict: &PyDictRef, filename: &str, vm: &VirtualMachine) -> PyResult<()> {
+    vm.import("importlib.machinery", 0)?;
+    let sys_modules = vm.sys_module.get_attr(identifier!(vm, modules), vm)?;
+    let machinery = sys_modules.get_item("importlib.machinery", vm)?;
+    let loader_class = machinery.get_attr("SourceFileLoader", vm)?;
+    let loader = loader_class.call((identifier!(vm, __main__).to_owned(), filename), vm)?;
+    module_dict.set_item("__loader__", loader, vm)?;
+    Ok(())
+}
+
 fn get_importer(path: &str, vm: &VirtualMachine) -> PyResult<Option<PyObjectRef>> {
     let path_importer_cache = vm.sys_module.get_attr("path_importer_cache", vm)?;
     let path_importer_cache = PyDictRef::try_from_object(vm, path_importer_cache)?;