Keep field defaults inside of _field_defaults and recreate the mutable ones

Author: isidentical

Lib/ast.py

@@ -102,18 +102,6 @@ def _convert(node):
         return _convert_signed_num(node)
     return _convert(node_or_string)
 
-@lru_cache
-def _field_defaults(node_type):
-    field_defaults = {}
-    for field, default in zip(node_type._fields, node_type._field_defaults):
-        if default == "?":
-            field_defaults[field] = None
-        elif default == "*":
-            field_defaults[field] = []
-        else:
-            field_defaults[field] = Ellipsis # sentinel
-    return field_defaults
-
 
 def dump(node, annotate_fields=True, include_attributes=False, *, indent=None, omit_defaults=True):
     """
@@ -142,14 +130,18 @@ def _format(node, level=0):
             args = []
             allsimple = True
             keywords = annotate_fields
-            field_defaults = _field_defaults(cls)
+            field_defaults = cls._field_defaults
             for name in node._fields:
                 try:
                     value = getattr(node, name)
                 except AttributeError:
                     keywords = True
                     continue
-                if omit_defaults and field_defaults[name] == value:
+                if (
+                    omit_defaults
+                    and name in field_defaults
+                    and field_defaults[name] == value
+                ):
                     keywords = True
                     continue
                 value, simple = _format(value, level)

Lib/test/test_ast.py

@@ -354,7 +354,7 @@ def test_field_attr_existence(self):
     def test_arguments(self):
         x = ast.FunctionDef()
         self.assertEqual(x._fields, ('name', 'args', 'body', 'decorator_list', 'returns', 'type_comment'))
-        self.assertEqual(x._field_defaults, ('', '', '*', '*', '?', '?'))
+        self.assertEqual(x._field_defaults, {'body': [], 'decorator_list': [], 'returns': None, 'type_comment': None})
 
         with self.assertRaises(AttributeError):
             x.name

Parser/asdl_c.py

@@ -614,9 +614,8 @@ def visitProduct(self, prod, name):
             for f in prod.fields:
                 self.emit('"%s",' % f.name, 1)
             self.emit("};", 0)
-            self.emit("static const char * const %s_field_defaults[]={" % name, 0)
-            for f in prod.fields:
-                self.emit('"%s",' % f.extra, 1)
+            self.emit("static const char %s_field_defaults[]={" % name, 0)
+            self.emit_field_defaults(prod.fields)
             self.emit("};", 0)
 
     def visitSum(self, sum, name):
@@ -645,11 +644,17 @@ def visitConstructor(self, cons, name):
             for t in cons.fields:
                 self.emit('"%s",' % t.name, 1)
             self.emit("};",0)
-            self.emit("static const char * const %s_field_defaults[]={" % cons.name, 0)
-            for t in cons.fields:
-                self.emit('"%s",' % t.extra, 1)
+            self.emit("static const char %s_field_defaults[]={" % cons.name, 0)
+            self.emit_field_defaults(cons.fields)
             self.emit("};",0)
 
+    def emit_field_defaults(self, fields):
+        for field in fields:
+            if field.extra:
+                self.emit("%r," % field.extra, 1)
+            else:
+                self.emit("' ',", 1)
+
 
 class PyTypesVisitor(PickleVisitor):
 
@@ -688,23 +693,6 @@ def visitModule(self, mod):
     return 0;
 }
 
-static inline PyObject *
-find_field_default(PyObject *field_default)
-{
-    if (PyUnicode_GET_LENGTH(field_default) < 1) {
-        return NULL;
-    }
-    switch (PyUnicode_READ_CHAR(field_default, 0)){
-        case '?':
-            Py_INCREF(Py_None);
-            return Py_None;
-        case '*':
-            return PyList_New(0);
-        default:
-            return NULL;
-    }
-}
-
 static int
 ast_type_init(PyObject *self, PyObject *args, PyObject *kw)
 {
@@ -752,25 +740,21 @@ def visitModule(self, mod):
                 goto cleanup;
         }
     }
-    PyObject *field, *raw_field_default, *field_default;
+    PyObject *field, *field_default;
     for (i = 0; i < numfields; i++) {
         field = PySequence_GetItem(fields, i);
         if (!field) {
             res = -1;
             goto cleanup;
         }
         int attr_present = PyObject_HasAttr(self, field);
+        field_default = PyDict_GetItem(field_defaults, field);
         Py_DECREF(field);
-        if (!attr_present) {
-            raw_field_default = PySequence_GetItem(field_defaults, i);
-            if (!raw_field_default) {
-                res = -1;
-                goto cleanup;
-            }
-            field_default = find_field_default(raw_field_default);
-            Py_DECREF(raw_field_default);
-            if (!field_default) {
-                continue;
+        if (!attr_present && field_default) {
+            if (PyList_Check(field_default)) {
+                field_default = PyList_New(0);
+            } else {
+                Py_INCREF(field_default);
             }
             res = PyObject_SetAttr(self, field, field_default);
             Py_DECREF(field_default);
@@ -843,7 +827,7 @@ def visitModule(self, mod):
     const char *type,
     PyObject* base,
     const char* const* fields,
-    const char* const* field_defaults,
+    const char* field_defaults,
     Py_ssize_t num_fields,
     const char *doc
 )
@@ -856,21 +840,29 @@ def visitModule(self, mod):
     if (!fnames) {
         goto exit;
     }
-    fdefaults = PyTuple_New(num_fields);
+    fdefaults = PyDict_New();
     if (!fdefaults) {
         goto exit;
     }
+    PyObject *field, *field_default;
     for (i = 0; i < num_fields; i++) {
-        PyObject *field = PyUnicode_InternFromString(fields[i]);
+        field = PyUnicode_InternFromString(fields[i]);
         if (!field) {
             goto exit;
         }
         PyTuple_SET_ITEM(fnames, i, field);
-        PyObject *field_default = PyUnicode_InternFromString(field_defaults[i]);
-        if (!field_default) {
-            goto exit;
+        if (field_defaults[i] == '?') {
+            field_default = Py_None;
+            Py_INCREF(field_default);
+        } else if (field_defaults[i] == '*') {
+            field_default = PyList_New(0);
+            if (!field_default) {
+                goto exit;
+            }
+        } else {
+            continue;
         }
-        PyTuple_SET_ITEM(fdefaults, i, field_default);
+        PyDict_SetItem(fdefaults, field, field_default);
     }
     result = PyObject_CallFunction((PyObject*)&PyType_Type, "s(O){OOOOOOOs}",
                     type, base,