cypher-codegen: account for fallback argument types in coalesce inference

[jbmusso]

Problem

coalesce(x, ...) inferred its result type as the first argument only, stripped of nullable — ignoring the fallback arguments. When a nullable Double property is coalesced with an integer literal (coalesce(n.score, 0)), the property's type (Double) wins, so the emitted column is Schema.Number. But at runtime, when the property is null, the database returns the integer literal 0 as an Integer object, which Schema.Number rejects → decode crash.

Fix

coalesce returns the first non-null argument, so the result type must unify the candidates:

• Walk arguments left→right, each stripped of nullable, stopping at the first non-nullable one (later args are unreachable).
• Unify scalars: equal types collapse to that type; two numeric scalars (Long/Double in any mix) collapse to Long — the integer-tolerant decoder is the numeric superset (accepts database integers, passes floats through); anything else keeps the leading argument's type.

So coalesce(<nullable Double>, 0) → Long, while coalesce(<non-null Double>, …) → Double and coalesce(<String>, …) → String are unchanged. The decoded TS type stays number, so there's no consumer type breakage.

Tests

• Red test: coalesce(s.nullableDouble, 0) must infer Long (failed before, returned Double).
• Regression guards (stay green): nullable Long, non-null Long, non-null String.
• Fixture uses a synthetic Sample vertex whose properties are named by their type/nullability role — no domain concepts.

Patch changeset included (0.4.1 → 0.4.2).

Generated with AI