Add PyFrame_GetVar() (#46)

vstinner · web-flow · commit 75b43a687129 · 2022-11-08T17:50:43.000+01:00
diff --git a/docs/api.rst b/docs/api.rst
@@ -24,6 +24,22 @@ Latest version of the header file:
 `pythoncapi_compat.h <https://raw.githubusercontent.com/python/pythoncapi-compat/master/pythoncapi_compat.h>`_.
 
 
+Python 3.12
+-----------
+
+.. c:function:: PyObject* PyFrame_GetVar(PyFrameObject *frame, PyObject *name)
+
+   See `PyFrame_GetVar() documentation <https://docs.python.org/dev/c-api/frame.html#c.PyFrame_GetVar>`__.
+
+   Not available on PyPy.
+
+.. c:function:: PyObject* PyFrame_GetVarString(PyFrameObject *frame, const char *name)
+
+   See `PyFrame_GetVarString() documentation <https://docs.python.org/dev/c-api/frame.html#c.PyFrame_GetVarString>`__.
+
+   Not available on PyPy.
+
+
 Python 3.11
 -----------
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
@@ -1,6 +1,8 @@
 Changelog
 =========
 
+* 2022-11-04: Add ``PyFrame_GetVar()`` and ``PyFrame_GetVarString()``
+  functions.
 * 2022-08-04: Add ``PyCode_GetVarnames()``, ``PyCode_GetFreevars()``
   and ``PyCode_GetCellvars()`` functions.
 * 2022-06-14: Fix compatibility with C++ older than C++11.
diff --git a/pythoncapi_compat.h b/pythoncapi_compat.h
@@ -242,6 +242,57 @@ PyFrame_GetLasti(PyFrameObject *frame)
 #endif
 
 
+// gh-91248 added PyFrame_GetVar() to Python 3.12.0a2
+#if PY_VERSION_HEX < 0x030C00A2 && !defined(PYPY_VERSION)
+PYCAPI_COMPAT_STATIC_INLINE(PyObject*)
+PyFrame_GetVar(PyFrameObject *frame, PyObject *name)
+{
+    PyObject *locals, *value;
+
+    locals = PyFrame_GetLocals(frame);
+    if (locals == NULL) {
+        return NULL;
+    }
+#if PY_VERSION_HEX >= 0x03000000
+    value = PyDict_GetItemWithError(locals, name);
+#else
+    value = PyDict_GetItem(locals, name);
+#endif
+    Py_DECREF(locals);
+
+    if (value == NULL) {
+        if (PyErr_Occurred()) {
+            return NULL;
+        }
+#if PY_VERSION_HEX >= 0x03000000
+        PyErr_Format(PyExc_NameError, "variable %R does not exist", name);
+#else
+        PyErr_SetString(PyExc_NameError, "variable does not exist");
+#endif
+        return NULL;
+    }
+    return Py_NewRef(value);
+}
+#endif
+
+
+// gh-91248 added PyFrame_GetVarString() to Python 3.12.0a2
+#if PY_VERSION_HEX < 0x030C00A2 && !defined(PYPY_VERSION)
+PYCAPI_COMPAT_STATIC_INLINE(PyObject*)
+PyFrame_GetVarString(PyFrameObject *frame, const char *name)
+{
+    PyObject *name_obj, *value;
+    name_obj = PyUnicode_FromString(name);
+    if (name_obj == NULL) {
+        return NULL;
+    }
+    value = PyFrame_GetVar(frame, name_obj);
+    Py_DECREF(name_obj);
+    return value;
+}
+#endif
+
+
 // bpo-39947 added PyThreadState_GetInterpreter() to Python 3.9.0a5
 #if PY_VERSION_HEX < 0x030900A5
 PYCAPI_COMPAT_STATIC_INLINE(PyInterpreterState *)
diff --git a/tests/test_pythoncapi_compat_cext.c b/tests/test_pythoncapi_compat_cext.c
@@ -3,6 +3,10 @@
 
 #include "pythoncapi_compat.h"
 
+#ifdef NDEBUG
+#  error "assertions must be enabled"
+#endif
+
 #ifdef Py_LIMITED_API
 #  error "Py_LIMITED_API is not supported"
 #endif
@@ -138,6 +142,41 @@ test_py_is(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
 
 
 #if !defined(PYPY_VERSION)
+static void
+test_frame_getvar(PyFrameObject *frame)
+{
+    // Make the assumption that test_frame_getvar() is only called by
+    // _run_tests() of test_pythoncapi_compat.py and so that the "name"
+    // variable exists.
+
+    // test PyFrame_GetVar() and PyFrame_GetVarString()
+    PyObject *attr = PyUnicode_FromString("name");
+    assert(attr != NULL);
+    PyObject *name1 = PyFrame_GetVar(frame, attr);
+    Py_DECREF(attr);
+    assert(name1 != NULL);
+    Py_DECREF(name1);
+
+    PyObject *name2 = PyFrame_GetVarString(frame, "name");
+    assert(name2 != NULL);
+    Py_DECREF(name2);
+
+    // test PyFrame_GetVar() and PyFrame_GetVarString() NameError
+    PyObject *attr3 = PyUnicode_FromString("dontexist");
+    assert(attr3 != NULL);
+    PyObject *name3 = PyFrame_GetVar(frame, attr3);
+    Py_DECREF(attr3);
+    assert(name3 == NULL);
+    assert(PyErr_ExceptionMatches(PyExc_NameError));
+    PyErr_Clear();
+
+    PyObject *name4 = PyFrame_GetVarString(frame, "dontexist");
+    assert(name4 == NULL);
+    assert(PyErr_ExceptionMatches(PyExc_NameError));
+    PyErr_Clear();
+}
+
+
 static PyObject *
 test_frame(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
 {
@@ -214,6 +253,10 @@ test_frame(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
     int lasti = PyFrame_GetLasti(frame);
     assert(lasti >= 0);
 
+    // test PyFrame_GetVar() and PyFrame_GetVarString()
+    test_frame_getvar(frame);
+
+    // done
     Py_DECREF(frame);
     Py_RETURN_NONE;
 }
