gh-106030: Miscellaneous fixes in Python/suggestions.c (GH-106031)

* PyDict_GetItem() and PyObject_HasAttr() suppress arbitrary errors and
should not be used.
* PyUnicode_CompareWithASCIIString() only works if the second argument
is ASCII string.
* Refleak in get_suggestions_for_name_error.
* Use of borrowed pointer after possible freeing (self).
* Add some missing error checks.

Author: serhiy-storchaka

Python/suggestions.c

@@ -151,15 +151,15 @@ calculate_suggestions(PyObject *dir,
  }
 for (inti=0; i<dir_size; ++i) {
 PyObject*item=PyList_GET_ITEM(dir, i);
+if (_PyUnicode_Equal(name, item)) {
+continue;
+ }
 Py_ssize_titem_size;
 constchar*item_str=PyUnicode_AsUTF8AndSize(item, &item_size);
 if (item_str==NULL) {
 PyMem_Free(buffer);
 returnNULL;
  }
-if (PyUnicode_CompareWithASCIIString(name, item_str) ==0) {
-continue;
- }
 // No more than 1/3 of the involved characters should need changed.
 Py_ssize_tmax_distance= (name_size+item_size+3) *MOVE_COST / 6;
 // Don't take matches we've already beaten.
@@ -220,37 +220,48 @@ get_suggestions_for_name_error(PyObject* name, PyFrameObject* frame)
 assert(code!=NULL&&code->co_localsplusnames!=NULL);
 
 PyObject*varnames=_PyCode_GetVarnames(code);
+Py_DECREF(code);
 if (varnames==NULL) {
 returnNULL;
  }
 PyObject*dir=PySequence_List(varnames);
 Py_DECREF(varnames);
-Py_DECREF(code);
 if (dir==NULL) {
 returnNULL;
  }
 
 // Are we inside a method and the instance has an attribute called 'name'?
-if (PySequence_Contains(dir, &_Py_ID(self)) >0) {
+intres=PySequence_Contains(dir, &_Py_ID(self));
+if (res<0) {
+ goto error;
+ }
+if (res>0) {
 PyObject*locals=PyFrame_GetLocals(frame);
 if (!locals) {
  goto error;
  }
-PyObject*self=PyDict_GetItem(locals, &_Py_ID(self)); /* borrowed */
-Py_DECREF(locals);
+PyObject*self=PyDict_GetItemWithError(locals, &_Py_ID(self)); /* borrowed */
 if (!self) {
+Py_DECREF(locals);
  goto error;
  }
 
-if (PyObject_HasAttr(self, name)) {
+PyObject*value;
+res=_PyObject_LookupAttr(self, name, &value);
+Py_DECREF(locals);
+if (res<0) {
+ goto error;
+ }
+if (value) {
+Py_DECREF(value);
 Py_DECREF(dir);
-returnPyUnicode_FromFormat("self.%S", name);
+returnPyUnicode_FromFormat("self.%U", name);
  }
  }
 
 PyObject*suggestions=calculate_suggestions(dir, name);
 Py_DECREF(dir);
-if (suggestions!=NULL) {
+if (suggestions!=NULL||PyErr_Occurred()) {
 returnsuggestions;
  }
 
@@ -260,7 +271,7 @@ get_suggestions_for_name_error(PyObject* name, PyFrameObject* frame)
  }
 suggestions=calculate_suggestions(dir, name);
 Py_DECREF(dir);
-if (suggestions!=NULL) {
+if (suggestions!=NULL||PyErr_Occurred()) {
 returnsuggestions;
  }
 
@@ -319,15 +330,16 @@ offer_suggestions_for_name_error(PyNameErrorObject *exc)
 assert(frame!=NULL);
 
 PyObject*suggestion=get_suggestions_for_name_error(name, frame);
-boolis_stdlib_module=is_name_stdlib_module(name);
-
-if (suggestion==NULL&& !is_stdlib_module) {
+if (suggestion==NULL&&PyErr_Occurred()) {
 returnNULL;
  }
 
 // Add a trailer ". Did you mean: (...)?"
 PyObject*result=NULL;
-if (!is_stdlib_module) {
+if (!is_name_stdlib_module(name)) {
+if (suggestion==NULL) {
+returnNULL;
+ }
 result=PyUnicode_FromFormat(". Did you mean: %R?", suggestion);
  } elseif (suggestion==NULL) {
 result=PyUnicode_FromFormat(". Did you forget to import %R?", name);