refactor: consolidate duplicated class-import logic between core/serialization and type_serialization

[davidsbatista]

Related Issues

• partly fixes #450

Proposed Changes:

• import_class_by_name (core/serialization.py) and deserialize_type (utils/type_serialization.py) each reimplemented the same "split a dotted path, import the module, getattr the class" logic.
• Moved the shared logic into type_serialization.py as _import_class_by_name
• While removing the now-unused logging import from core/serialization.py, caught a real bug: components/tools/tool_invoker.py was accidentally importing logging through core/serialization.py instead of from haystack directly
• Fixed that import to go straight to haystack.logging

How did you test it?

• Ran the full test suite, all tests pass, including the ones that caught the tool_invoker.py regression before it shipped.

Notes for the reviewer

• import_class_by_name is now a one-line wrapper around _import_class_by_name which is private to type_serialization.py, and 9 files import import_class_by_name from core/serialization.py
• Keeping this wrapper avoids either exposing a private name externally or touching 9 call sites for no functional gain.
• Same pattern exists for deserialize_chatgenerator_inplace wrapping deserialize_component_inplace
• Happy to discuss if we should change this

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:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: 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.
• I have run pre-commit hooks and fixed any issue.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
haystack-docs	Ignored	Preview	Jul 7, 2026 1:00pm

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
haystack/components/tools
tool_invoker.py
haystack/core
serialization.py
haystack/utils
type_serialization.py					188-189
Project Total

This report was generated by python-coverage-comment-action

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.