Add createReducer default handler

[rafael81]

Summary

• add .defaultHandler() to the createReducer chain API for remaining unhandled actions
• preserve the explicit handlers map while carrying default-handler behavior through chained reducers
• skip Redux initialization actions by default, with an opt-in flag when initialization should use the default handler
• add runtime, dts-jest, snapshot, and README coverage

Fixes #156

Validation

• npm run ci-check

Notes

This revives the closed default-handler feature request with a fresh implementation against current master. The prior PR #241 is closed; I kept this PR focused on the API proposed in the issue and added tests for runtime behavior plus remaining-action typing.

Transparency

I used AI assistance to inspect the old discussion and closed PR, draft the implementation and tests, and review the final diff. I manually ran the validation command before submitting.

Funded issue

• IssueHunt $80 issue: https://oss.issuehunt.io/r/piotrwitek/typesafe-actions/issues/156

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IssueHunt Summary

Referenced issues

This pull request has been submitted to:

• #156: Add default handler in createReducer

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[gemini-code-assist]

Code Review

This pull request introduces a defaultHandler method to the createReducer API, allowing for a fallback reducer when no specific action handlers match. The implementation includes support for opting into Redux initialization actions, updated type definitions, and comprehensive unit tests. Feedback was provided to broaden the internal Redux action exclusion regex to ensure all internal lifecycle actions, such as probes, are handled correctly by default.

[gemini-code-assist]

The regex currently only matches Redux initialization actions starting with @@redux/INIT. However, Redux also dispatches other internal actions like @@redux/PROBE_UNKNOWN_ACTION during store creation to verify reducer behavior. It is generally safer to exclude all actions starting with @@redux/ from the default handler to avoid unexpected behavior during Redux's internal lifecycle.

Suggested change

	const initializationActionTypes = /^@@redux\/INIT/;
	const initializationActionTypes = /^@@redux\//;

[rafael81]

Addressed the review by broadening the default exclusion from only @@redux/INIT to all @@redux/ internal actions, and added coverage for @@redux/PROBE_UNKNOWN_ACTION in both the default and opt-in paths.\n\nValidation: npm run ci-check passed locally.