Add Interpreter.get().

python · ericsnowcurrently · Nov 6, 2023 · Sep 21, 2023 · Oct 5, 2023 · Oct 24, 2023
commit 283ddab1dd9d58ccd2deb880b7a7d32bf3c4d98b
diff --git a/Lib/test/support/interpreters.py b/Lib/test/support/interpreters.py
@@ -112,6 +112,16 @@ def bind(self, ns=None, /, **kwargs):
         ns = dict(ns, **kwargs) if ns is not None else kwargs
         _interpreters.set___main___attrs(self._id, ns)
 
+    # XXX getattr?
+    def get(self, name, default=None, /):
+        """Return the attr value from the interpreter's __main__.
+
+        The value must be shareable.
+        """
+        found = _interpreters.get___main___attrs(self._id, (name,), default)
+        assert len(found) == 1, found
+        return found[name]
+
     # XXX Rename "run" to "exec"?
     # XXX Do not allow init to overwrite (by default)?
     def run(self, src_str, /, *, init=None):

diff --git a/Lib/test/test_interpreters.py b/Lib/test/test_interpreters.py
@@ -526,6 +526,36 @@ def test_not_shareable(self):
             interp.run('print(spam)')
 
 
+class TestInterpreterGet(TestBase):
+
+    def test_empty(self):
+        interp = interpreters.create()
+        with self.assertRaises(TypeError):
+            interp.get()
+
+    def test_found(self):
+        interp = interpreters.create()
+        obj1 = interp.get('__name__')
+        interp.bind(spam=42)
+        obj2 = interp.get('spam')
+
+        self.assertEqual(obj1, '__main__')
+        self.assertEqual(obj2, 42)
+
+    def test_not_found(self):
+        interp = interpreters.create()
+        obj1 = interp.get('spam')
+        obj2 = interp.get('spam', 'eggs')
+
+        self.assertIs(obj1, None)
+        self.assertEqual(obj2, 'eggs')
+
+    def test_not_shareable(self):
+        interp = interpreters.create()
+        with self.assertRaises(ValueError):
+            interp.get('__builtins__')
+
+
 class TestInterpreterRun(TestBase):
 
     def test_success(self):

diff --git a/Modules/_xxsubinterpretersmodule.c b/Modules/_xxsubinterpretersmodule.c
@@ -456,6 +456,84 @@ PyDoc_STRVAR(set___main___attrs_doc,
 \n\
 Bind the given attributes in the interpreter's __main__ module.");
 
+static PyObject *
+interp_get___main___attrs(PyObject *self, PyObject *args)
+{
+    PyObject *id, *names;
+    PyObject *dflt = Py_None;
+    if (!PyArg_ParseTuple(args, "OO|O:" MODULE_NAME ".get___main___attrs",
+                          &id, &names, &dflt))
+    {
+        return NULL;
+    }
+
+    // Look up the interpreter.
+    PyInterpreterState *interp = PyInterpreterID_LookUp(id);
+    if (interp == NULL) {
+        return NULL;
+    }
+
+    // Prep the result.
+    PyObject *found = PyDict_New();
+    if (found == NULL) {
+        return NULL;
+    }
+
+    // Set up the shared ns.
+    _PyXI_namespace *shared = _PyXI_NamespaceFromNames(names);
+    if (shared == NULL) {
+        if (!PyErr_Occurred()) {
+            PyErr_SetString(PyExc_ValueError, "expected non-empty list of names");
+        }
+        Py_DECREF(found);
+        return NULL;
+    }
+
+    _PyXI_session session = {0};
+
+    // Prep and switch interpreters, including apply the updates.
+    if (_PyXI_Enter(&session, interp, NULL) < 0) {
+        Py_DECREF(found);
+        assert(!PyErr_Occurred());
+        _PyXI_ApplyCapturedException(&session, NULL);
+        assert(PyErr_Occurred());
+        return NULL;
+    }
+
+    // Extract the requested attrs from __main__.
+    int res = _PyXI_FillNamespaceFromDict(shared, session.main_ns, &session);
+
+    // Clean up and switch back.
+    _PyXI_Exit(&session);
+
+    if (res == 0) {
+        assert(!PyErr_Occurred());
+        // Copy the objects into the result dict.
+        if (_PyXI_ApplyNamespace(shared, found, dflt) < 0) {
+            Py_CLEAR(found);
+        }
+    }
+    else {
+        if (!PyErr_Occurred()) {
+            _PyXI_ApplyCapturedException(&session, NULL);
+            assert(PyErr_Occurred());
+        }
+        else {
+            assert(!_PyXI_HasCapturedException(&session));
+        }
+        Py_CLEAR(found);
+    }
+
+    _PyXI_FreeNamespace(shared);
+    return found;
+}
+
+PyDoc_STRVAR(get___main___attrs_doc,
+"get___main___attrs(id, names, default=None, /)\n\
+\n\
+Look up the given attributes in the interpreter's __main__ module.\n\
+Return the default if not found.");
+
 static PyUnicodeObject *
 convert_script_arg(PyObject *arg, const char *fname, const char *displayname,
                    const char *expected)
@@ -754,6 +832,8 @@ static PyMethodDef module_functions[] = {
 
     {"set___main___attrs",        _PyCFunction_CAST(interp_set___main___attrs),
      METH_VARARGS, set___main___attrs_doc},
+    {"get___main___attrs",        _PyCFunction_CAST(interp_get___main___attrs),
+     METH_VARARGS, get___main___attrs_doc},
     {"is_shareable",              _PyCFunction_CAST(object_is_shareable),
      METH_VARARGS | METH_KEYWORDS, is_shareable_doc},