feat: add serialization to State / move State to agents.state

[Amnah199]

Related Issues

• fixes Add serialization/deserialization support to State #9286

Proposed Changes:

• Introduce serialize_value and deserialize_value utility methods in the utils module. These methods encapsulate logic that is also used in the breakpoints de/serialization logic and tracing.utils.coerce_tag_value (except the json load). Once the breakpoints feature is merged in haystack, it can reuse these centralized utility functions.
• Add serialization and deserialization logic to the State class.
• Move the State class to the utils module, as it is not actually a data class. A deprecation warning is added to the existing State class in the dataclasses module to guide users toward the updated implementation.

How did you test it?

Moved the existing tests to test_utils_state.py and added two new tests for serialization and deserialization.

[coveralls]

Pull Request Test Coverage Report for Build 15205617087

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 59 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-0.1%) to 90.244%

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Files with Coverage Reduction	New Missed Lines	%
components/agents/init.py	1	75.0%
utils/init.py	2	33.33%
components/agents/agent.py	10	91.07%
dataclasses/state_utils.py	11	0.0%
utils/base_serialization.py	16	86.99%
components/tools/tool_invoker.py	19	83.59%

Totals
Change from base Build 15205079200:	-0.1%
Covered Lines:	11257
Relevant Lines:	12474

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💛 - Coveralls

[Amnah199]

I’ve kept the current haystack.dataclasses.State file for backward compatibility. However, the tests from test.dataclasses.test_state.py have been moved to utils, so we could consider removing this test file. Alternatively, we might keep it temporarily for safety until the old State class is fully removed.

[sjrl]

@Amnah199 a general question for you.

While working on this did you find that we are missing to_dict and from_dict methods from dataclasses/components/etc. that would be helpful to add? For example, I noticed we don't have a from_dict or to_dict method for ByteStream.

[sjrl]

Looks great! Thanks for all of the work on this!

[sjrl]

@Amnah199 sorry last comment, should we make this method private for now so it's easy to change in the future if need be?

[Amnah199]

Good idea, until we have more confidence in this!