fix(livecodebench): expose .buffer on mocked stdin/stdout

ais_bench/benchmark/datasets/livecodebench/testing_util.py

@@ -63,11 +63,43 @@ def timeout_handler(signum, frame):
 # used to capture stdout as a list
 # from https://stackoverflow.com/a/16571630/6416660
 # alternative use redirect_stdout() from contextlib
+class _StdoutWithBuffer(StringIO):
+    """StringIO that also exposes a binary ``.buffer`` view, like real stdout.
+
+    Generated solutions often use ``sys.stdout.buffer.write(...)`` for fast
+    output. A plain StringIO has no ``buffer`` attribute, so such solutions
+    used to fail with an AttributeError and were counted as runtime errors.
+    The bytes written through ``.buffer`` are decoded and forwarded to this
+    same StringIO, so ``getvalue()`` still returns the complete output.
+    """
+
+    class _Buffer:
+
+        def __init__(self, owner):
+            self._owner = owner
+
+        def write(self, data):
+            if isinstance(data, (bytes, bytearray)):
+                data = data.decode()
+            return self._owner.write(data)
+
+        def writelines(self, lines):
+            for line in lines:
+                self.write(line)
+
+        def flush(self):
+            pass
+
+    def __init__(self):
+        super().__init__()
+        self.buffer = _StdoutWithBuffer._Buffer(self)
+
+
 class Capturing(list):
 
     def __enter__(self):
         self._stdout = sys.stdout
-        sys.stdout = self._stringio = StringIO()
+        sys.stdout = self._stringio = _StdoutWithBuffer()
         # Make closing the StringIO a no-op
         self._stringio.close = lambda x: 1
         return self

tests/UT/datasets/livecodebench/test_livecodebench.py

@@ -427,6 +427,62 @@ def test_load_with_cot(self):
             self.assertIn('train', result)
 
 
+class TestStdIOBuffer(unittest.TestCase):
+    """测试标准输入/输出的二进制 .buffer 视图
+
+    竞赛类题解常用 sys.stdin.buffer.read() / sys.stdout.buffer.write() 做快速
+    读写，评测时伪造的 stdin/stdout 必须提供 .buffer，否则这类题解会抛
+    AttributeError 被误判为 Runtime Error。
+    """
+
+    @classmethod
+    def setUpClass(cls):
+        try:
+            from ais_bench.benchmark.datasets.livecodebench import testing_util
+            cls.testing_util = testing_util
+        except ImportError:
+            raise unittest.SkipTest('testing_util not available')
+
+    def _run(self, source, inputs):
+        namespace = {}
+        exec(compile(source, '<generated>', 'exec'), namespace)
+        with self.testing_util.Capturing() as output:
+            self.testing_util.call_method(namespace['main'], inputs)
+        return ''.join(output).strip()
+
+    def test_stdin_buffer_read(self):
+        """sys.stdin.buffer.read() 应读到测试输入"""
+        source = ('import sys\n'
+                  'def main():\n'
+                  '    data = sys.stdin.buffer.read().split()\n'
+                  '    print(sum(map(int, data)))\n')
+        self.assertEqual(self._run(source, '1 2\n3\n'), '6')
+
+    def test_stdin_buffer_readline(self):
+        """sys.stdin.buffer.readline() 应按行读到测试输入"""
+        source = ('import sys\n'
+                  'def main():\n'
+                  '    n = int(sys.stdin.buffer.readline())\n'
+                  '    print(n * 2)\n')
+        self.assertEqual(self._run(source, '21\n'), '42')
+
+    def test_stdout_buffer_write(self):
+        """sys.stdout.buffer.write() 的输出应被 Capturing 收集到"""
+        source = ('import sys\n'
+                  'def main():\n'
+                  '    sys.stdout.buffer.write(b"42\\n")\n')
+        self.assertEqual(self._run(source, ''), '42')
+
+    def test_mixed_text_and_binary_output(self):
+        """混用 print 和 sys.stdout.buffer.write 时输出顺序应保持一致"""
+        source = ('import sys\n'
+                  'def main():\n'
+                  '    print("a")\n'
+                  '    sys.stdout.buffer.write(b"b\\n")\n'
+                  '    print("c")\n')
+        self.assertEqual(self._run(source, ''), 'a\nb\nc')
+
+
 if __name__ == '__main__':
     unittest.main()