test_recursion.py

import weakref
import sys
from test import support
from test.test_json import PyTest, CTest


class JSONTestObject:
    pass
class TestRecursion:
    def test_listrecursion(self):
        x = []
        x.append(x)
        try:
            self.dumps(x)
        except ValueError as exc:
            self.assertEqual(exc.__notes__, ["when serializing list item 0"])
        else:
            self.fail("didn't raise ValueError on list recursion")
        x = []
        y = [x]
        x.append(y)
        try:
            self.dumps(x)
        except ValueError as exc:
            self.assertEqual(exc.__notes__, ["when serializing list item 0"]*2)
        else:
            self.fail("didn't raise ValueError on alternating list recursion")
        y = []
        x = [y, y]
        # ensure that the marker is cleared
        self.dumps(x)

    def test_dictrecursion(self):
        x = {}
        x["test"] = x
        try:
            self.dumps(x)
        except ValueError as exc:
            self.assertEqual(exc.__notes__, ["when serializing dict item 'test'"])
        else:
            self.fail("didn't raise ValueError on dict recursion")
        x = {}
        y = {"a": x, "b": x}
        # ensure that the marker is cleared
        self.dumps(x)

    def test_defaultrecursion(self):
        class RecursiveJSONEncoder(self.json.JSONEncoder):
            recurse = False
            def default(self, o):
                if o is JSONTestObject:
                    if self.recurse:
                        return [JSONTestObject]
                    else:
                        return 'JSONTestObject'
                return self.json.JSONEncoder.default(o)

        enc = RecursiveJSONEncoder()
        self.assertEqual(enc.encode(JSONTestObject), '"JSONTestObject"')
        enc.recurse = True
        try:
            enc.encode(JSONTestObject)
        except ValueError as exc:
            self.assertEqual(exc.__notes__,
                             ["when serializing list item 0",
                              "when serializing type object"])
        else:
            self.fail("didn't raise ValueError on default recursion")


    @support.skip_if_unlimited_stack_size
    @support.skip_emscripten_stack_overflow()
    @support.skip_wasi_stack_overflow()
    def test_highly_nested_objects_decoding(self):
        very_deep = 500_000
        # test that loading highly-nested objects doesn't segfault when C
        # accelerations are used. See #12017
        with self.assertRaises(RecursionError):
            with support.infinite_recursion():
                self.loads('{"a":' * very_deep + '1' + '}' * very_deep)
        with self.assertRaises(RecursionError):
            with support.infinite_recursion():
                self.loads('{"a":' * very_deep + '[1]' + '}' * very_deep)
        with self.assertRaises(RecursionError):
            with support.infinite_recursion():
                self.loads('[' * very_deep + '1' + ']' * very_deep)

    @support.skip_if_unlimited_stack_size
    @support.skip_wasi_stack_overflow()
    @support.skip_emscripten_stack_overflow()
    @support.requires_resource('cpu')
    def test_highly_nested_objects_encoding(self):
        # See #12051
        l, d = [], {}
        for x in range(500_000):
            l, d = [l], {'k':d}
        with self.assertRaises(RecursionError):
            with support.infinite_recursion(5000):
                self.dumps(l)
        with self.assertRaises(RecursionError):
            with support.infinite_recursion(5000):
                self.dumps(d)

    @support.skip_if_unlimited_stack_size
    @support.skip_emscripten_stack_overflow()
    @support.skip_wasi_stack_overflow()
    def test_endless_recursion(self):
        # See #12051
        class EndlessJSONEncoder(self.json.JSONEncoder):
            def default(self, o):
                """If check_circular is False, this will keep adding another list."""
                return [o]

        with self.assertRaises(RecursionError):
            with support.infinite_recursion(1000):
                EndlessJSONEncoder(check_circular=False).encode(5j)

    @support.skip_if_unlimited_stack_size
    @support.skip_emscripten_stack_overflow()
    @support.skip_wasi_stack_overflow()
    def test_memory_leak_on_recursion_error(self):
        # Test that no memory leak occurs when a RecursionError is raised.
        class LeakTestObj:
            pass

        weak_refs = []
        def default(obj):
            if isinstance(obj, LeakTestObj):
                new_obj = LeakTestObj()
                weak_refs.append(weakref.ref(new_obj))
                return [new_obj]
            raise TypeError

        depth = min(500, sys.getrecursionlimit() - 10)
        obj = LeakTestObj()
        for _ in range(depth):
            obj = [obj]

        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")
        for i, ref in enumerate(weak_refs):
            self.assertIsNone(ref(), f"object {i} still alive")

class TestPyRecursion(TestRecursion, PyTest): pass
class TestCRecursion(TestRecursion, CTest): pass