fix: pass elem writer to JSON array membership dialect methods

[richardwooding]

Problem

Dialect.writeJSONArrayMembership and Dialect.writeNestedJSONArrayMembership received only the array expression. The caller (Converter.visitInJSONArray) emitted elem = <dialect-output> inline, which worked accidentally for PostgreSQL but was silently broken for every other dialect:

Dialect	Generated SQL (before)	Correct?
PostgreSQL	elem = ANY(ARRAY(SELECT jsonb_array_elements_text(arr)))	✅
MySQL	elem = JSON_CONTAINS(arr, CAST(? AS JSON)) — compares elem to 0/1	❌
SQLite	elem = (SELECT value FROM json_each(arr)) — scalar subquery returns last row for multi-element arrays	❌
DuckDB	elem = (SELECT value FROM json_each(arr)) — same multi-row scalar subquery bug	❌
BigQuery	elem = UNNEST(JSON_VALUE_ARRAY(arr)) — = UNNEST() is invalid syntax	❌
Spark	throws ConversionException — couldn't build a boolean predicate without the element	❌

The Spark throw (added in PR #10) was the canary that revealed the contract was broken: it needed the element to emit array_contains(...) but the interface didn't provide it.

Fix

Widen both method signatures to accept writeElem alongside writeArray. The converter no longer emits elem = itself; each dialect now owns the full boolean predicate.

New signatures:

void writeJSONArrayMembership(StringBuilder w, String jsonFunc, SqlWriter writeElem, SqlWriter writeArray) throws ConversionException;
void writeNestedJSONArrayMembership(StringBuilder w, SqlWriter writeElem, SqlWriter writeArray) throws ConversionException;

Generated SQL per dialect (after)

Dialect	Generated SQL
PostgreSQL	elem = ANY(ARRAY(SELECT jsonb_array_elements_text(arr)))
MySQL	JSON_OVERLAPS(JSON_ARRAY(elem), arr) — consistent with writeArrayMembership
SQLite	EXISTS (SELECT 1 FROM json_each(arr) WHERE value = elem)
DuckDB	EXISTS (SELECT 1 FROM json_each(arr) WHERE value = elem)
BigQuery	elem IN UNNEST(JSON_VALUE_ARRAY(arr))
Spark	array_contains(from_json(arr, 'ARRAY<STRING>'), elem)

Changes

• Dialect.java — interface signature widened (breaking change for external implementors)
• Converter.java::visitInJSONArray — removed inline elem = prefix, passes () -> visit(elem) as new arg
• All 6 dialect implementations updated
• Cel2SqlSparkTest.jsonArrayMembershipThrowsClearly renamed to jsonArrayMembershipEmitsArrayContains and rewritten to assert correct SQL instead of asserting a throw

Testing

./gradlew build passes (compile + all unit tests green).

Note: there are no existing unit tests that exercise the JSON-array-membership code path via visitInJSONArray (those paths require a Schema or a jsonVariables option to route through visitInJSONArray). The Spark dialect-level test directly exercises the new method signature. Integration tests for full end-to-end coverage of the MySQL/SQLite/DuckDB paths can be added in a follow-up.

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Generated by Claude Code