fix: preserve dict subclass types in _deepcopy_with_exceptions

[inchang-ing]

Related Issues

• fixes _deepcopy_with_exceptions turns dict subclasses (defaultdict, OrderedDict, Counter) into plain dict, so pipeline inputs lose their type #13092

Proposed Changes:

_deepcopy_with_exceptions rebuilt every dict with a dict comprehension, so any dict subclass came back as a plain dict:

if isinstance(obj, dict):
    return {k: _deepcopy_with_exceptions(v) for k, v in obj.items()}

A defaultdict lost its default_factory, an OrderedDict lost its ordering guarantee, and a Counter was demoted to dict. The list/tuple/set branch right above already preserves the concrete type via type(obj)(...), and the namedtuple special case (see the release note fix-deepcopy-namedtuple-*) does the same, so dict subclasses were the remaining gap. Because Pipeline.run copies its inputs with this helper, a component could receive a different type than the caller passed in.

The dict branch now rebuilds the container as its own type instead of a plain dict:

if isinstance(obj, dict):
    result = copy(obj)
    result.clear()
    result.update((k, _deepcopy_with_exceptions(v)) for k, v in obj.items())
    return result

A plain copy is used rather than type(obj)(<iterable>) because dict subclasses have incompatible constructors (defaultdict takes default_factory as its first positional argument), so a generic iterable-based rebuild is not safe. Copying the (empty) container preserves the subclass and all of its configuration — including defaultdict.default_factory — and refilling it with deep-copied values keeps the deep-copy semantics identical to the plain-dict path.

How did you test it?

Added TestDeepcopyWithFallback cases in test/core/pipeline/test_utils.py:

• a parametrized case over defaultdict, OrderedDict and Counter asserting the type is preserved and the values are deep-copied;
• a case asserting a defaultdict keeps its default_factory (a missing key still triggers the factory instead of raising KeyError).

Verified the tests fail on main (the type assertion sees dict instead of the subclass) and pass with the change.

Notes for the reviewer

• copy(obj) on a plain dict returns a plain dict, so existing behavior for the common case is unchanged.
• Contributes a release note (releasenotes/notes/fix-deepcopy-dict-subclass-*.yaml), matching the earlier namedtuple fix.

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
• I've used one of the conventional commit types for my PR title: fix: and added ! in case the PR includes breaking changes.
• I have documented my code.
• I have added a release note file, following the contributors guidelines.

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