Fix test to use infinite_recursion pattern and catch RecursionError

- Use support.infinite_recursion() context manager
- Catch RecursionError explicitly instead of all exceptions
- Fix import order with two blank lines after from imports
- Remove extra blank lines in _json.c
- Use Py_DECREF instead of Py_XDECREF

Author: okiemute04

Lib/test/test_json/test_recursion.py

@@ -3,10 +3,9 @@
 from test import support
 from test.test_json import PyTest, CTest
 
+
 class JSONTestObject:
     pass
-
-
 class TestRecursion:
     def test_listrecursion(self):
         x = []
@@ -137,10 +136,9 @@ def default(obj):
         for _ in range(depth):
             obj = [obj]
 
-        try:
-            self.dumps(obj, default=default)
-        except Exception:
-            pass
+        with support.infinite_recursion():
+            with self.assertRaises(RecursionError):
+                self.dumps(obj, default=default)
 
         support.gc_collect()
         self.assertTrue(weak_refs, "No objects were created to track")

Modules/_json.c

@@ -1646,21 +1646,19 @@ encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
         rv = encoder_listencode_obj(s, writer, newobj, indent_level, indent_cache);
         _Py_LeaveRecursiveCall();
         Py_DECREF(newobj);
-
         if (rv) {
             if (ident != NULL) {
                 int del_rv = PyDict_DelItem(s->markers, ident);
-                Py_XDECREF(ident);
+                Py_DECREF(ident);
                 if (del_rv < 0) {
                     return -1;
                 }
             }
             return -1;
         }
-
         if (ident != NULL) {
             int del_rv = PyDict_DelItem(s->markers, ident);
-            Py_XDECREF(ident);
+            Py_DECREF(ident);
             if (del_rv < 0) {
                 return -1;
             }