fix: re-raise existing exception when available (#667)

msgpack/_unpacker.pyx

@@ -205,7 +205,10 @@ def unpackb(object packed, *, object object_hook=None, object list_hook=None,
         raise FormatError
     elif ret == -3:
         raise StackError
-    raise ValueError("Unpack failed: error = %d" % (ret,))
+    elif PyErr_Occurred():
+        raise
+    else:
+        raise ValueError("Unpack failed: error = %d" % (ret,))
 
 
 cdef class Unpacker:
@@ -481,6 +484,8 @@ cdef class Unpacker:
                 raise FormatError
             elif ret == -3:
                 raise StackError
+            elif PyErr_Occurred():
+                raise
             else:
                 raise ValueError("Unpack failed: error = %d" % (ret,))
 

test/test_except.py

@@ -4,7 +4,7 @@ import datetime
 
 from pytest import raises
 
-from msgpack import FormatError, OutOfData, StackError, Unpacker, packb, unpackb
+from msgpack import ExtType, FormatError, OutOfData, StackError, Unpacker, packb, unpackb
 
 
 class DummyException(Exception):
@@ -32,6 +32,34 @@ def test_raise_from_object_hook():
     )
 
 
+def test_raise_from_list_hook():
+    def hook(lst: list) -> list:
+        raise DummyException
+
+    with raises(DummyException):
+        unpackb(packb([1, 2, 3]), list_hook=hook)
+
+    with raises(DummyException):
+        unpacker = Unpacker(list_hook=hook)
+        unpacker.feed(packb([1, 2, 3]))
+        unpacker.unpack()
+
+
+def test_raise_from_ext_hook():
+    def hook(code: int, data: bytes) -> ExtType:
+        raise DummyException
+
+    packed = packb(ExtType(42, b"hello"))
+
+    with raises(DummyException):
+        unpackb(packed, ext_hook=hook)
+
+    with raises(DummyException):
+        unpacker = Unpacker(ext_hook=hook)
+        unpacker.feed(packed)
+        unpacker.unpack()
+
+
 def test_invalidvalue():
     incomplete = b"\xd9\x97#DL_"  # raw8 - length=0x97
     with raises(ValueError):