JSON Schema validation in Node.js core

[mertcanaltin]

What is the problem this feature will solve?

Hi all,

I wanted to open a discussion about whether JSON Schema validation could be a useful addition to Node.js core.

Current state

• Node.js currently has no built-in JSON Schema validation
• node.config.json (experimental) uses hand-written type checking against a JSON Schema 2020-12 definition generated from C++ option metadata
• package.json parsing uses simdjson but has no schema validation, fields are extracted structurally
• The only schema validation in the Node.js tree lives inside deps/npm (Ajv)

Potential use cases

• Validate node.config.json against its own schema properly
• Future validation for package.json fields (opt-in, non-breaking)
• Expose as a built-in module (node:jsonschema) so userland doesn't need to pull in external validators

Context

I've been working on a project in this area, ata-validator, a JSON Schema validator built on simdjson and RE2. It currently passes 96.9% of the official JSON Schema Test Suite (Draft 2020-12) and falls back to a pure JS engine when native bindings aren't available.

I'm not proposing to land it as-is, I'd love to hear from the group first:

1. Is there interest in having JSON Schema validation available in core?
2. What would be the most useful entry point? (config validation, public API, both?)
3. Any concerns about the dependency story? (RE2/abseil weight, simdjson already in core)

Happy to share benchmarks or more details if this sounds worth exploring.

fyi @Qard

What is the feature you are proposing to solve the problem?

A built-in JSON Schema validator, potentially exposed as node:jsonschema, that could also be used internally for validating node.config.json and other configuration files.

This would provide Node.js users with a fast, native JSON Schema (Draft 2020-12) validation capability without needing external dependencies.

What alternatives have you considered?

• Continuing with hand-written validation for each config format individually,
  doesn't scale as more config formats are added

• Bundling an existing JS-based validator like Ajv into core, lacks native performance benefits

• Leaving JSON Schema validation entirely to userland

[nabeel378]

This sounds interesting! Having built-in validation for node.config.json
against its existing schema would be a practical first step. Looking forward
to seeing the benchmarks.

[marco-ippolito]

Would like to see the validation for node.config.json

[SukeshP1995]

It is sad to see that only ajv is the popular library for json-scema validation. I would like to have native json-schema validation in node itself.

[mertcanaltin]

Would like to see the validation for node.config.json

I've discussed this with @Qard as well, starting with node.config.json validation sounds like a great first step.
I'll work on a draft PR for that

[Qard]

We've already discussed it privately, but I think this is worth at least evaluating having it in core. The current design seems to align very well with our performance efforts, even relying on some libraries we already depend on. So the lift to integrate this seems low while the benefit seems high given how many apps need to do input validation and the cost it can have. I also think it's a fairly mechanical need and not like typical libraries where design opinions could be involved--jsonschema works a particular way, and it's a widely accepted standard, so having it in core I think makes sense.

[mertcanaltin]

I opened a PR for node.config.json #62603