fix: rebuild namedtuples in _deepcopy_with_exceptions (#11981)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: chuenchen309

haystack/core/pipeline/utils.py

@@ -33,6 +33,11 @@ def _deepcopy_with_exceptions(obj: Any) -> Any:
     from haystack.tools.tool import Tool
     from haystack.tools.toolset import Toolset
 
+    # namedtuples are tuple subclasses whose __new__ takes the fields positionally,
+    # so they must be rebuilt by unpacking rather than from a single iterable.
+    if isinstance(obj, tuple) and hasattr(obj, "_fields"):
+        return type(obj)(*(_deepcopy_with_exceptions(v) for v in obj))
+
     if isinstance(obj, (list, tuple, set)):
         return type(obj)(_deepcopy_with_exceptions(v) for v in obj)
 

releasenotes/notes/fix-deepcopy-namedtuple-c7aa157bc9aef85b.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Fixed ``_deepcopy_with_exceptions`` crashing when a value is a ``namedtuple``
+    (or any ``typing.NamedTuple``). The list/tuple/set branch rebuilt the
+    container with ``type(obj)(<generator>)``, but a namedtuple's ``__new__``
+    expects its fields as positional arguments rather than a single iterable, so
+    copying a component input or parameter that contained a namedtuple raised a
+    ``TypeError``. Namedtuples are now rebuilt by unpacking their deep-copied
+    fields.

test/core/pipeline/test_utils.py

@@ -4,6 +4,7 @@
 
 import logging
 import warnings
+from collections import namedtuple
 
 import pytest
 
@@ -255,6 +256,19 @@ def test_deepcopy_with_fallback_component(self, monkeypatch):
         res = _deepcopy_with_exceptions(original)
         assert res["component"] is original["component"]
 
+    def test_deepcopy_with_fallback_namedtuple(self):
+        Point = namedtuple("Point", ["x", "y"])
+        inner = Copyable()
+        original = {"point": Point(inner, 2)}
+        copy = _deepcopy_with_exceptions(original)
+        # A namedtuple must be reconstructed as its own type. Its __new__ takes
+        # positional fields, so the plain ``type(obj)(<generator>)`` path used for
+        # lists/tuples/sets would raise a TypeError instead of copying it.
+        assert isinstance(copy["point"], Point)
+        assert copy["point"].y == 2
+        # Its contents are deep-copied, matching how plain tuples are handled.
+        assert copy["point"].x is not original["point"].x
+
 
 class TestArgsDeprecated:
     @pytest.fixture