fix(rds): star columns, empty where objects, nullable limit/offset

[bentsku]

Motivation

A customer's AppSync JS resolver calling select({ table, columns: ['*'], limit, offset }) from @aws-appsync/utils/rds fails in several ways. Root causes in this library:

1. columns: ['*'] rendered SELECT "*", which PostgreSQL rejects with column "*" does not exist (SQLState 42703). AWS leaves a bare * unquoted.
2. An empty where object ({} or {and: []}) emitted a dangling WHERE keyword — SELECT ... WHERE LIMIT :P0 → syntax error at or near "LIMIT" (SQLState 42601) — in SELECT, UPDATE, and DELETE statements. AWS omits the clause entirely.
3. limit: 0 / offset: 0 were silently dropped by truthy checks. AWS emits them as parameters.

(The remaining customer symptom — a TypeError when the query has no arguments at all — is a ctx.args construction issue in the AppSync provider, not in this library, and is handled separately.)

Changes

• rds/index.js:
  • quoteIdentifier(): a bare * stays unquoted. Note AWS does quote a qualified star (persons.* → "persons"."*"), so only the exact string * is special-cased.
  • SELECT/UPDATE/DELETE: skip the WHERE keyword when the built clause is empty.
  • limit/offset: nullish checks (!= null) so 0 is emitted and null/omitted is skipped.
• __tests__/helpers.js: the local harness now exposes ctx.args as {} when the context carries no arguments, matching the AppSync runtime (verified: AWS EvaluateCode normalizes ctx.args even for an entirely empty context).
• __tests__/resolvers.test.js: new select statement edge cases describe block (10 tests), including the customer's exact resolver shape. All new snapshots recorded from real AWS AppSync EvaluateCode.
• package.json: version bump to 0.1.3.

Verification

• npm test: 85 passed, 83 snapshots (10 newly AWS-recorded).
• End-to-end against the customer reproduction sample with LocalStack Pro dev + APPSYNC_JS_LIBS_VERSION=fix-rds-utils: the DatabaseErrorException is gone and the generated statement executes (SELECT * FROM "domain"."color" LIMIT :P0).

🤖 Generated with Claude Code