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gh-121141: add support for copy.replace to AST nodes (#121162)
This commit is contained in:
Bénédikt Tran
GitHub
parent
94f50f8ee6
commit
9728ead361
5 changed files with 837 additions and 2 deletions
279
Python/Python-ast.c
generated
279
Python/Python-ast.c
generated
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@ -6,7 +6,9 @@
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#include "pycore_ceval.h" // _Py_EnterRecursiveCall
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#include "pycore_lock.h" // _PyOnceFlag
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#include "pycore_interp.h" // _PyInterpreterState.ast
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#include "pycore_modsupport.h" // _PyArg_NoPositional()
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#include "pycore_pystate.h" // _PyInterpreterState_GET()
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#include "pycore_setobject.h" // _PySet_NextEntry(), _PySet_Update()
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#include "pycore_unionobject.h" // _Py_union_type_or
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#include "structmember.h"
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#include <stddef.h>
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@ -5331,6 +5333,279 @@ cleanup:
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return result;
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}
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/*
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* Perform the following validations:
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*
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* - All keyword arguments are known 'fields' or 'attributes'.
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* - No field or attribute would be left unfilled after copy.replace().
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*
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* On success, this returns 1. Otherwise, set a TypeError
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* exception and returns -1 (no exception is set if some
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* other internal errors occur).
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*
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* Parameters
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*
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* self The AST node instance.
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* dict The AST node instance dictionary (self.__dict__).
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* fields The list of fields (self._fields).
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* attributes The list of attributes (self._attributes).
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* kwargs Keyword arguments passed to ast_type_replace().
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*
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* The 'dict', 'fields', 'attributes' and 'kwargs' arguments can be NULL.
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*
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* Note: this function can be removed in 3.15 since the verification
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* will be done inside the constructor.
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*/
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static inline int
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ast_type_replace_check(PyObject *self,
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PyObject *dict,
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PyObject *fields,
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PyObject *attributes,
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PyObject *kwargs)
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{
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// While it is possible to make some fast paths that would avoid
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// allocating objects on the stack, this would cost us readability.
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// For instance, if 'fields' and 'attributes' are both empty, and
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// 'kwargs' is not empty, we could raise a TypeError immediately.
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PyObject *expecting = PySet_New(fields);
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if (expecting == NULL) {
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return -1;
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}
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if (attributes) {
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if (_PySet_Update(expecting, attributes) < 0) {
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Py_DECREF(expecting);
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return -1;
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}
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}
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// Any keyword argument that is neither a field nor attribute is rejected.
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// We first need to check whether a keyword argument is accepted or not.
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// If all keyword arguments are accepted, we compute the required fields
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// and attributes. A field or attribute is not needed if:
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//
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// 1) it is given in 'kwargs', or
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// 2) it already exists on 'self'.
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if (kwargs) {
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Py_ssize_t pos = 0;
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PyObject *key, *value;
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while (PyDict_Next(kwargs, &pos, &key, &value)) {
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int rc = PySet_Discard(expecting, key);
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if (rc < 0) {
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Py_DECREF(expecting);
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return -1;
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}
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if (rc == 0) {
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PyErr_Format(PyExc_TypeError,
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"%.400s.__replace__ got an unexpected keyword "
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"argument '%U'.", Py_TYPE(self)->tp_name, key);
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Py_DECREF(expecting);
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return -1;
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}
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}
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}
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// check that the remaining fields or attributes would be filled
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if (dict) {
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Py_ssize_t pos = 0;
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PyObject *key, *value;
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while (PyDict_Next(dict, &pos, &key, &value)) {
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// Mark fields or attributes that are found on the instance
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// as non-mandatory. If they are not given in 'kwargs', they
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// will be shallow-coied; otherwise, they would be replaced
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// (not in this function).
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if (PySet_Discard(expecting, key) < 0) {
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Py_DECREF(expecting);
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return -1;
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}
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}
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if (attributes) {
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// Some attributes may or may not be present at runtime.
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// In particular, now that we checked whether 'kwargs'
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// is correct or not, we allow any attribute to be missing.
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//
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// Note that fields must still be entirely determined when
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// calling the constructor later.
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PyObject *unused = PyObject_CallMethodOneArg(expecting,
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&_Py_ID(difference_update),
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attributes);
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if (unused == NULL) {
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Py_DECREF(expecting);
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return -1;
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}
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Py_DECREF(unused);
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}
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}
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// Now 'expecting' contains the fields or attributes
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// that would not be filled inside ast_type_replace().
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Py_ssize_t m = PySet_GET_SIZE(expecting);
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if (m > 0) {
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PyObject *names = PyList_New(m);
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if (names == NULL) {
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Py_DECREF(expecting);
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return -1;
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}
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Py_ssize_t i = 0, pos = 0;
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PyObject *item;
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Py_hash_t hash;
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while (_PySet_NextEntry(expecting, &pos, &item, &hash)) {
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PyObject *name = PyObject_Repr(item);
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if (name == NULL) {
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Py_DECREF(expecting);
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Py_DECREF(names);
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return -1;
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}
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// steal the reference 'name'
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PyList_SET_ITEM(names, i++, name);
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}
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Py_DECREF(expecting);
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if (PyList_Sort(names) < 0) {
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Py_DECREF(names);
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return -1;
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}
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PyObject *sep = PyUnicode_FromString(", ");
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if (sep == NULL) {
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Py_DECREF(names);
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return -1;
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}
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PyObject *str_names = PyUnicode_Join(sep, names);
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Py_DECREF(sep);
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Py_DECREF(names);
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if (str_names == NULL) {
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return -1;
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}
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PyErr_Format(PyExc_TypeError,
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"%.400s.__replace__ missing %ld keyword argument%s: %U.",
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Py_TYPE(self)->tp_name, m, m == 1 ? "" : "s", str_names);
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Py_DECREF(str_names);
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return -1;
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}
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else {
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Py_DECREF(expecting);
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return 1;
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}
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}
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/*
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* Python equivalent:
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*
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* for key in keys:
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* if hasattr(self, key):
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* payload[key] = getattr(self, key)
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*
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* The 'keys' argument is a sequence corresponding to
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* the '_fields' or the '_attributes' of an AST node.
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*
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* This returns -1 if an error occurs and 0 otherwise.
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*
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* Parameters
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*
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* payload A dictionary to fill.
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* keys A sequence of keys or NULL for an empty sequence.
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* dict The AST node instance dictionary (must not be NULL).
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*/
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static inline int
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ast_type_replace_update_payload(PyObject *payload,
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PyObject *keys,
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PyObject *dict)
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{
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assert(dict != NULL);
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if (keys == NULL) {
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return 0;
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}
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Py_ssize_t n = PySequence_Size(keys);
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if (n == -1) {
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return -1;
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}
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for (Py_ssize_t i = 0; i < n; i++) {
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PyObject *key = PySequence_GetItem(keys, i);
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if (key == NULL) {
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return -1;
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}
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PyObject *value;
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if (PyDict_GetItemRef(dict, key, &value) < 0) {
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Py_DECREF(key);
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return -1;
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}
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if (value == NULL) {
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Py_DECREF(key);
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// If a field or attribute is not present at runtime, it should
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// be explicitly given in 'kwargs'. If not, the constructor will
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// issue a warning (which becomes an error in 3.15).
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continue;
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}
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int rc = PyDict_SetItem(payload, key, value);
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Py_DECREF(key);
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Py_DECREF(value);
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if (rc < 0) {
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return -1;
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}
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}
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return 0;
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}
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/* copy.replace() support (shallow copy) */
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static PyObject *
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ast_type_replace(PyObject *self, PyObject *args, PyObject *kwargs)
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{
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if (!_PyArg_NoPositional("__replace__", args)) {
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return NULL;
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}
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struct ast_state *state = get_ast_state();
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if (state == NULL) {
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return NULL;
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}
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PyObject *result = NULL;
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// known AST class fields and attributes
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PyObject *fields = NULL, *attributes = NULL;
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// current instance dictionary
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PyObject *dict = NULL;
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// constructor positional and keyword arguments
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PyObject *empty_tuple = NULL, *payload = NULL;
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PyObject *type = (PyObject *)Py_TYPE(self);
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if (PyObject_GetOptionalAttr(type, state->_fields, &fields) < 0) {
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goto cleanup;
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}
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if (PyObject_GetOptionalAttr(type, state->_attributes, &attributes) < 0) {
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goto cleanup;
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}
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if (PyObject_GetOptionalAttr(self, state->__dict__, &dict) < 0) {
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goto cleanup;
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}
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if (ast_type_replace_check(self, dict, fields, attributes, kwargs) < 0) {
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goto cleanup;
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}
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empty_tuple = PyTuple_New(0);
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if (empty_tuple == NULL) {
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goto cleanup;
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}
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payload = PyDict_New();
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if (payload == NULL) {
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goto cleanup;
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}
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if (dict) { // in case __dict__ is missing (for some obscure reason)
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// copy the instance's fields (possibly NULL)
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if (ast_type_replace_update_payload(payload, fields, dict) < 0) {
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goto cleanup;
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}
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// copy the instance's attributes (possibly NULL)
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if (ast_type_replace_update_payload(payload, attributes, dict) < 0) {
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goto cleanup;
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}
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}
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if (kwargs && PyDict_Update(payload, kwargs) < 0) {
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goto cleanup;
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}
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result = PyObject_Call(type, empty_tuple, payload);
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cleanup:
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Py_XDECREF(payload);
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Py_XDECREF(empty_tuple);
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Py_XDECREF(dict);
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Py_XDECREF(attributes);
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Py_XDECREF(fields);
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return result;
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}
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static PyMemberDef ast_type_members[] = {
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{"__dictoffset__", Py_T_PYSSIZET, offsetof(AST_object, dict), Py_READONLY},
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{NULL} /* Sentinel */
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@ -5338,6 +5613,10 @@ static PyMemberDef ast_type_members[] = {
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static PyMethodDef ast_type_methods[] = {
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{"__reduce__", ast_type_reduce, METH_NOARGS, NULL},
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{"__replace__", _PyCFunction_CAST(ast_type_replace), METH_VARARGS | METH_KEYWORDS,
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PyDoc_STR("__replace__($self, /, **fields)\n--\n\n"
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"Return a copy of the AST node with new values "
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"for the specified fields.")},
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{NULL}
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};
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