Accept "ev" as a conventional event parameter name (#4562)

[jeremydmiller]

Follow-up to the event-source-generator naming work for JasperFx/marten#4562.

What

CodeGenerationExtensions.GetEventType is the single shared rule that all projection types (SingleStreamProjection, MultiStreamProjection, and EventProjection) use to decide which parameter of a conventional method is the event. When the event can't be inferred by type alone (more than one candidate parameter), it falls back to the conventional event parameter name.

This adds "ev" to the accepted names, alongside the existing @event, event, and e — ev is a common shorthand and there's no reason to reject it.

// all four now resolve the event parameter when type inference is ambiguous:
public void Apply(SomeEvent @event, MyAggregate agg) { }
public void Apply(SomeEvent ev, MyAggregate agg) { }
public void Apply(SomeEvent e, MyAggregate agg) { }

Notes

• For the overwhelmingly common case (a single concrete event parameter, with session/operations as interfaces), the event is still inferred by type — no special parameter name is required. The name convention only matters as a disambiguator.
• Added a focused unit test covering @event, e, and ev disambiguation.
• The naming convention itself is being documented clearly in companion docs PRs for Marten (including the 9.0 migration guide) and Polecat.

🤖 Generated with Claude Code