Add the eager-runtime hook required by Python 3.15 importlib (#8946)

* Add the eager-runtime importlib lazy-attribute hook

Expose _imp._set_lazy_attributes(modobj, name, /), used by CPython 3.15 importlib after eager loading. Match its empty pending-lazy-module registry behavior, including name type and string-subclass hashing checks. This does not implement lazy imports or change the target version or bundled libraries.

Assisted-by: Codex:model-version-unavailable

* Consolidate lazy import hook tests into stdlib_imp

Move the distinct direct-hook argument and hashing contracts into the existing _imp snippet and remove the separate file. Preserve every pre-existing assertion and the CPython version guard; canonical 3.15 lazy-import tests already cover feature-level registry and reification behavior.

Assisted-by: Codex:model-version-unavailable

crates/vm/src/stdlib/_imp.rs

@@ -193,7 +193,7 @@ fn find_frozen(name: &str, vm: &VirtualMachine) -> Result<FrozenModule, FrozenEr
 #[pymodule(with(lock))]
 mod _imp {
     use crate::{
-        PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
+        AsObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
         builtins::{PyBytesRef, PyCode, PyMemoryView, PyModule, PyStrRef, PyUtf8StrRef},
         import, version,
     };
@@ -214,6 +214,19 @@ mod _imp {
         Vec::new()
     }
 
+    // CPython removes the name from its pending lazy-module registry here.
+    // RustPython currently performs only eager imports, so that registry is empty.
+    #[pyfunction]
+    fn _set_lazy_attributes(
+        _modobj: PyObjectRef,
+        name: PyStrRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        // Even an empty set checks the hash of a str subclass.
+        name.as_object().hash(vm)?;
+        Ok(())
+    }
+
     #[pyfunction]
     fn is_builtin(name: PyUtf8StrRef, vm: &VirtualMachine) -> bool {
         vm.state.module_defs.contains_key(name.as_str())

extra_tests/snippets/stdlib_imp.py

@@ -1,7 +1,7 @@
 import _imp
 import time as import_time
 
-from testutils import assert_raises
+from testutils import assert_raises, skip_if_unsupported
 
 assert _imp.is_builtin("time") == True
 assert _imp.is_builtin("os") == False
@@ -42,3 +42,45 @@ data, ispkg, origname = _imp.find_frozen("__hello__", withdata=True)
 assert ispkg is False
 assert origname == "__hello__"
 assert _imp.get_frozen_object("__hello__", data).co_name == "<module>"
+
+
+def test_lazy_attributes_eager_registry():
+    # CPython accepts any first argument and a string name. In an eager-only
+    # interpreter there are no pending lazy module names to remove.
+    for modobj in (None, object(), {}, 42):
+        assert _imp._set_lazy_attributes(modobj, "package.module") is None
+        assert _imp._set_lazy_attributes(modobj, "\ud800") is None
+
+    for name in (None, 1, b"package.module", [], {}):
+        with assert_raises(TypeError):
+            _imp._set_lazy_attributes(None, name)
+
+    with assert_raises(TypeError):
+        _imp._set_lazy_attributes(modobj=None, name="package.module")
+
+    class ModuleName(str):
+        hashes = 0
+
+        def __hash__(self):
+            self.hashes += 1
+            return 42
+
+    name = ModuleName("package.module")
+    assert _imp._set_lazy_attributes(None, name) is None
+    assert name.hashes == 1
+
+    class UnhashableName(str):
+        __hash__ = None
+
+    with assert_raises(TypeError):
+        _imp._set_lazy_attributes(None, UnhashableName("package.module"))
+
+    class HashErrorName(str):
+        def __hash__(self):
+            raise RuntimeError("name hash failed")
+
+    with assert_raises(RuntimeError):
+        _imp._set_lazy_attributes(None, HashErrorName("package.module"))
+
+
+skip_if_unsupported(3, 15, test_lazy_attributes_eager_registry)