fix!: remove upcast

[yordis]

No description provided.

[coderabbitai]

Walkthrough

This PR removes the Upcasting feature from Commanded by deleting the Upcast and Upcaster modules, removing upcasting logic from core event handlers and aggregates, eliminating related test support code, and updating documentation to reflect the removal.

Changes

Cohort / File(s)	Summary
Documentation updates guides/explanations/events.md, guides/explanations/fork-differences.md, guides/howtos/migrating-from-v1-to-v2.md	Removed "Upcasting events" explanatory sections and examples from events guide; added "Removed Upcasting Support" section to fork-differences documenting the removal and introducing EnrichedMetadata struct; deleted upcasting migration guidance.
Core upcasting modules deleted lib/commanded/event/upcast.ex, lib/commanded/event/upcaster.ex	Deleted entire Upcast module with upcast_event_stream/2 and upcast_event/2 functions; deleted Upcaster protocol with upcast/2 callback and Any implementation.
Upcasting logic removal lib/commanded/aggregates/aggregate.ex, lib/commanded/event/handler.ex, lib/commanded/event_store.ex	Removed Upcast alias and replaced upcasting pipeline with direct event processing; stream_forward no longer upcasts events; removed application extraction tied to upcasting.
Project configuration mix.exs	Removed Commanded.Event.Upcaster from public API documentation exports.
Test support deletion test/event/support/upcast/*, test/event/upcaster_test.exs	Deleted all upcasting test modules including BatchEventHandler, EventHandler, UpcastAggregate, and Events with their Upcaster implementations; removed entire UpcasterTest suite.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Verify removal completeness: Ensure no lingering references to Upcast/Upcaster modules remain in codebase or imports.
• Handler and aggregate logic: Confirm event processing pipelines function correctly after replacing Upcast.upcast_event_stream with direct processor invocation.
• Documentation consistency: Check that fork-differences accurately reflects all API changes and new EnrichedMetadata struct is properly documented elsewhere.

Possibly related PRs

• feat: add batch support #18: Extends event handler batch processing with an Upcast.BatchEventHandler test helper that is being deleted in this PR.
• chore: add fork diff explanation #25: Previously added the fork-differences documentation section that this PR directly modifies with the "Removed Upcasting Support" subsection.

Poem

🐰 Upcasting fades to history's past,
Simpler streams shall hold more fast,
No more transformations, clean and lean,
Commanded's now more keen, I've seen! ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.
Description Check	❓ Inconclusive	No pull request description was provided by the author. The check instructions state this should be a lenient check that passes as long as the description is not completely off-topic, but they assume a description exists. An absent description provides no information to evaluate whether it is related to the changeset, making it impossible to conclusively determine if it meets the pass criterion (description related to changeset) or the fail criterion (completely unrelated). This falls into the inconclusive category where insufficient information is available to make a determination.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The PR title "fix!: remove upcast" directly and accurately summarizes the main change in the pull request. The changeset comprehensively removes upcasting functionality throughout the codebase, including the removal of Commanded.Event.Upcast and Commanded.Event.Upcaster modules, elimination of upcasting logic from handlers and aggregates, removal of related documentation sections, and deletion of all test support code for upcasting. The title is concise, clear, and specific enough that teammates scanning history would immediately understand the primary change.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch yordis/remove-upcasting

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3ad1e98 and af830a0.

📒 Files selected for processing (14)

• guides/explanations/events.md (0 hunks)
• guides/explanations/fork-differences.md (7 hunks)
• guides/howtos/migrating-from-v1-to-v2.md (0 hunks)
• lib/commanded/aggregates/aggregate.ex (0 hunks)
• lib/commanded/event/handler.ex (3 hunks)
• lib/commanded/event/upcast.ex (0 hunks)
• lib/commanded/event/upcaster.ex (0 hunks)
• lib/commanded/event_store.ex (1 hunks)
• mix.exs (0 hunks)
• test/event/support/upcast/batch_event_handler.ex (0 hunks)
• test/event/support/upcast/event_handler.ex (0 hunks)
• test/event/support/upcast/events.ex (0 hunks)
• test/event/support/upcast/upcast_aggregate.ex (0 hunks)
• test/event/upcaster_test.exs (0 hunks)

💤 Files with no reviewable changes (11)

• test/event/support/upcast/upcast_aggregate.ex
• test/event/support/upcast/batch_event_handler.ex
• guides/explanations/events.md
• guides/howtos/migrating-from-v1-to-v2.md
• lib/commanded/event/upcast.ex
• test/event/support/upcast/event_handler.ex
• mix.exs
• lib/commanded/event/upcaster.ex
• lib/commanded/aggregates/aggregate.ex
• test/event/upcaster_test.exs
• test/event/support/upcast/events.ex

🔇 Additional comments (4)

lib/commanded/event/handler.ex (2)

953-973: LGTM: Event processing now bypasses upcasting.

The changes correctly remove the upcasting pipeline:

• Events are passed directly to the processor function
• The processor signature now explicitly receives events as the first argument
• Both :event and :batch callback paths work correctly with raw events

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1416-1436: LGTM: Partition logic correctly accesses raw event data.

The partition_event function now directly accesses the event's data field, which is the correct approach after removing upcasting. The metadata enrichment and error handling remain intact.

guides/explanations/fork-differences.md (1)

29-36: LGTM: Breaking change properly documented.

The documentation clearly describes:

• What was removed (Upcast and Upcaster modules, integration with handlers/aggregates)
• The rationale (schema transformations can be handled explicitly in handlers)
• The breaking nature of this change

This provides users with clear information about the impact of upgrading to this version.

lib/commanded/event_store.ex (1)

82-82: LGTM: Upcasting removed from stream processing.

Verification confirms the stream is now returned directly without transformation, and all Upcast references have been successfully removed from the codebase. The change is correct and aligns with the PR's goal.

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