bpo-42152: Use PyDict_Contains and PyDict_SetDefault if appropriate. (GH-22986)

If PyDict_GetItemWithError is only used to check whether the key is in dict,
it is better to use PyDict_Contains instead.

And if it is used in combination with PyDict_SetItem, PyDict_SetDefault can
replace the combination.

1 files changed, 22 insertions, 23 deletions

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 00d6ab3be2..faa8696153 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -2544,8 +2544,8 @@ PyDict_MergeFromSeq2(PyObject *d, PyObject *seq2, int override)
                 goto Fail;
             }
         }
-        else if (PyDict_GetItemWithError(d, key) == NULL) {
-            if (PyErr_Occurred() || PyDict_SetItem(d, key, value) < 0) {
+        else {
+            if (PyDict_SetDefault(d, key, value) == NULL) {
                 Py_DECREF(key);
                 Py_DECREF(value);
                 goto Fail;
@@ -2660,19 +2660,20 @@ dict_merge(PyObject *a, PyObject *b, int override)
                 Py_INCREF(value);
                 if (override == 1)
                     err = insertdict(mp, key, hash, value);
-                else if (_PyDict_GetItem_KnownHash(a, key, hash) == NULL) {
-                    if (PyErr_Occurred()) {
-                        Py_DECREF(value);
-                        Py_DECREF(key);
-                        return -1;
+                else {
+                    err = _PyDict_Contains_KnownHash(a, key, hash);
+                    if (err == 0) {
+                        err = insertdict(mp, key, hash, value);
+                    }
+                    else if (err > 0) {
+                        if (override != 0) {
+                            _PyErr_SetKeyError(key);
+                            Py_DECREF(value);
+                            Py_DECREF(key);
+                            return -1;
+                        }
+                        err = 0;
                     }
-                    err = insertdict(mp, key, hash, value);
-                }
-                else if (override != 0) {
-                    _PyErr_SetKeyError(key);
-                    Py_DECREF(value);
-                    Py_DECREF(key);
-                    return -1;
                 }
                 Py_DECREF(value);
                 Py_DECREF(key);
@@ -2709,18 +2710,16 @@ dict_merge(PyObject *a, PyObject *b, int override)
 
         for (key = PyIter_Next(iter); key; key = PyIter_Next(iter)) {
             if (override != 1) {
-                if (PyDict_GetItemWithError(a, key) != NULL) {
-                    if (override != 0) {
+                status = PyDict_Contains(a, key);
+                if (status != 0) {
+                    if (status > 0) {
+                        if (override == 0) {
+                            Py_DECREF(key);
+                            continue;
+                        }
                         _PyErr_SetKeyError(key);
-                        Py_DECREF(key);
-                        Py_DECREF(iter);
-                        return -1;
                     }
                     Py_DECREF(key);
-                    continue;
-                }
-                else if (PyErr_Occurred()) {
-                    Py_DECREF(key);
                     Py_DECREF(iter);
                     return -1;
                 }