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.

3 files changed, 29 insertions, 24 deletions

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 89b7fce..1ce55b6 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -924,12 +924,12 @@ builtin_eval_impl(PyObject *module, PyObject *source, PyObject *globals,
         return NULL;
     }
 
-    if (_PyDict_GetItemIdWithError(globals, &PyId___builtins__) == NULL) {
-        if (_PyDict_SetItemId(globals, &PyId___builtins__,
-                              PyEval_GetBuiltins()) != 0)
-            return NULL;
+    int r = _PyDict_ContainsId(globals, &PyId___builtins__);
+    if (r == 0) {
+        r = _PyDict_SetItemId(globals, &PyId___builtins__,
+                              PyEval_GetBuiltins());
     }
-    else if (PyErr_Occurred()) {
+    if (r < 0) {
         return NULL;
     }
 
@@ -1012,12 +1012,12 @@ builtin_exec_impl(PyObject *module, PyObject *source, PyObject *globals,
             Py_TYPE(locals)->tp_name);
         return NULL;
     }
-    if (_PyDict_GetItemIdWithError(globals, &PyId___builtins__) == NULL) {
-        if (_PyDict_SetItemId(globals, &PyId___builtins__,
-                              PyEval_GetBuiltins()) != 0)
-            return NULL;
+    int r = _PyDict_ContainsId(globals, &PyId___builtins__);
+    if (r == 0) {
+        r = _PyDict_SetItemId(globals, &PyId___builtins__,
+                              PyEval_GetBuiltins());
     }
-    else if (PyErr_Occurred()) {
+    if (r < 0) {
         return NULL;
     }
 
diff --git a/Python/errors.c b/Python/errors.c
index 02cf479..f80ae21 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -1098,10 +1098,11 @@ PyErr_NewException(const char *name, PyObject *base, PyObject *dict)
             goto failure;
     }
 
-    if (_PyDict_GetItemIdWithError(dict, &PyId___module__) == NULL) {
-        if (_PyErr_Occurred(tstate)) {
-            goto failure;
-        }
+    int r = _PyDict_ContainsId(dict, &PyId___module__);
+    if (r < 0) {
+        goto failure;
+    }
+    if (r == 0) {
         modulename = PyUnicode_FromStringAndSize(name,
                                              (Py_ssize_t)(dot-name));
         if (modulename == NULL)
diff --git a/Python/import.c b/Python/import.c
index 26b80f3..b79bda0 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1018,14 +1018,14 @@ module_dict_for_exec(PyThreadState *tstate, PyObject *name)
     /* If the module is being reloaded, we get the old module back
        and re-use its dict to exec the new code. */
     d = PyModule_GetDict(m);
-    if (_PyDict_GetItemIdWithError(d, &PyId___builtins__) == NULL) {
-        if (_PyErr_Occurred(tstate) ||
-            _PyDict_SetItemId(d, &PyId___builtins__,
-                              PyEval_GetBuiltins()) != 0)
-        {
-            remove_module(tstate, name);
-            return NULL;
-        }
+    int r = _PyDict_ContainsId(d, &PyId___builtins__);
+    if (r == 0) {
+        r = _PyDict_SetItemId(d, &PyId___builtins__,
+                              PyEval_GetBuiltins());
+    }
+    if (r < 0) {
+        remove_module(tstate, name);
+        return NULL;
     }
 
     return d;  /* Return a borrowed reference. */
@@ -1660,10 +1660,14 @@ resolve_name(PyThreadState *tstate, PyObject *name, PyObject *globals, int level
             goto error;
         }
 
-        if (_PyDict_GetItemIdWithError(globals, &PyId___path__) == NULL) {
+        int haspath = _PyDict_ContainsId(globals, &PyId___path__);
+        if (haspath < 0) {
+            goto error;
+        }
+        if (!haspath) {
             Py_ssize_t dot;
 
-            if (_PyErr_Occurred(tstate) || PyUnicode_READY(package) < 0) {
+            if (PyUnicode_READY(package) < 0) {
                 goto error;
             }