perf: skip the Ajv schema lookup on every anyOf/oneOf/if validation - #926

Proposal:

• Fetch the Ajv validation function of each anyOf / oneOf / if schema once per serializer, instead of looking it up on every serialization.

Problem:

For anyOf, oneOf and if/then/else the generated code calls validator.validate(schemaRef, value) to pick the branch. That goes through ajv.validate(ref, data). Ajv compiles each schema once and keeps the validation function, but it looks that function up again on every call: it normalizes the ref with a regular expression, reads it from its schemas / refs registries, and after the validation copies the errors to ajv.errors. On small values that lookup costs more than the validation itself.

This is the path taken by every nullable property written as anyOf: [{ type: 'string' }, { type: 'null' }], which is what TypeBox emits for Type.Union([Type.String(), Type.Null()]).

Change:

• index.js: each schema ref used by the generated code gets one variable in the serializer scope. The call site becomes (validate_0 || (validate_0 = validator.getSchemaValidator(ref)))(value), so the function is fetched on first use and then called directly. A ref validated in several places shares one variable.
• lib/validator.js: new getSchemaValidator(schemaRef), which returns the function from ajv.getSchema() and throws the same no schema with key or ref error as ajv.validate() when the ref is unknown. validate() is unchanged.
• lib/standalone.js: the inlined validator object exposes the same method.

Schemas are still compiled lazily, on first use; compileValidators and the standalone modes work as before. The output does not change.

Tests:

test/compile-validators.test.js: nothing is looked up at build time, each schema is looked up once after eleven serializations, a shared schema uses one variable, and getSchemaValidator throws on an unknown ref. The existing assertions on the generated code are updated to the new call.

Benchmark:

Apple Silicon, default mechanism on both sides, median ops/sec over 15 alternating rounds, output consumed with Buffer.byteLength.

Node.js 26.12.0 (V8 14.6):

Node.js 24.22.0 (V8 13.6):

Node.js 22.23.1 (V8 12.4):

The last row is a control: the user profile schema of benchmark/fixtures/api-responses has no anyOf / oneOf / if, so its generated code does not change.

Note:

• semver-patch. No option or type change. Validator#validate is kept, so standalone files generated by earlier versions keep working.
• Independent from the objectMechanism: 'native' fix: the two PRs touch different files and can be merged in any order.