gh-159465: Share incomplete-input error cleanup

Author: pablogsal

Include/internal/pycore_parser.h

@@ -27,7 +27,7 @@ _Py_DECLARE_STR(empty, "")
         }, \
     }
 
-/* If incomplete is non-NULL, initialize *incomplete to NULL. A returned AST
+/* The caller must initialize *incomplete to NULL if supplied. A returned AST
    can also return an owned exception there for a missing line terminator.
    Validate the AST before reporting that exception. */
 extern struct _mod* _PyParser_ASTFromString(

Parser/tokenizer/decoder.c

@@ -300,25 +300,24 @@ store_prepared_source(struct tok_state *tok, const char *data, Py_ssize_t len,
         int add_newline = add_final_newline &&
             pos + raw_line_len == len && !terminated;
         const char *line = data + pos;
-        Py_ssize_t line_len = raw_line_len;
         // raw_line_length stops at the first CR or LF, so any CR is in
         // the line terminator.
         Py_ssize_t terminator_len = 0;
         if (!preserve_crlf) {
-            if (line[line_len - 1] == '\r') {
+            if (line[raw_line_len - 1] == '\r') {
                 terminator_len = 1;
             }
-            else if (line_len > 1 && line[line_len - 2] == '\r') {
+            else if (raw_line_len > 1 && line[raw_line_len - 2] == '\r') {
                 terminator_len = 2;
             }
         }
         _PyTok_Off appended;
         if (terminator_len || add_newline) {
             appended = _PyTok_SourceAppendLineWithNewline(
-                &tok->source, line, line_len - terminator_len);
+                &tok->source, line, raw_line_len - terminator_len);
         }
         else {
-            appended = _PyTok_SourceAppendLine(&tok->source, line, line_len);
+            appended = _PyTok_SourceAppendLine(&tok->source, line, raw_line_len);
         }
         if (appended < 0) {
             tok->done = PyErr_ExceptionMatches(PyExc_MemoryError)

Python/pythonrun.c

@@ -1569,46 +1569,43 @@ _Py_CompileString(const char *str, PyObject *filename, int start,
         return NULL;
     }
 
-    PyCodeObject *co;
-    mod_ty mod;
     PyArena *arena = _PyArena_New();
     if (arena == NULL)
         return NULL;
 
+    PyObject *result = NULL;
     PyObject *incomplete = NULL;
-    mod = _PyParser_ASTFromString(str, filename, start, flags, arena, module,
-                                 &incomplete);
+    mod_ty mod = _PyParser_ASTFromString(str, filename, start, flags, arena,
+                                        module, &incomplete);
     if (mod == NULL) {
-        _PyArena_Free(arena);
-        return NULL;
+        goto done;
     }
     if (flags && (flags->cf_flags & PyCF_ONLY_AST)) {
         int syntax_check_only = ((flags->cf_flags & PyCF_OPTIMIZED_AST) == PyCF_ONLY_AST); /* unoptiomized AST */
         if (_PyCompile_AstPreprocess(mod, filename, flags, optimize, arena,
                                      syntax_check_only, module) < 0)
         {
-            Py_XDECREF(incomplete);
-            _PyArena_Free(arena);
-            return NULL;
+            goto done;
         }
         if (incomplete != NULL) {
-            _PyArena_Free(arena);
-            PyErr_SetRaisedException(incomplete);
-            return NULL;
+            goto done;
         }
-        PyObject *result = PyAST_mod2obj(mod);
+        result = PyAST_mod2obj(mod);
         _PyArena_Free(arena);
         return result;
     }
-    co = _PyAST_Compile(mod, filename, flags, optimize, arena, module);
+    result = (PyObject *)_PyAST_Compile(mod, filename, flags, optimize, arena, module);
+
+done:
     _PyArena_Free(arena);
-    if (co != NULL && incomplete != NULL) {
-        Py_DECREF(co);
+    if (incomplete != NULL && !PyErr_Occurred()) {
+        Py_CLEAR(result);
         PyErr_SetRaisedException(incomplete);
-        return NULL;
     }
-    Py_XDECREF(incomplete);
-    return (PyObject *)co;
+    else {
+        Py_XDECREF(incomplete);
+    }
+    return result;
 }
 
 PyObject *