go-helpers VS typescript-json-schema

```

The "IsInteger" validator can of course be interpreted as a type, the important thing is though that it can be customized using type parameters and that we can add any number of additional validators that do advanced things (e.g. we could define an "IsPrime" validator that checks for primality of the number).

I find this more elegant than having both a "type" field and various extensions for validations that you need to remember. The validator list mechanism also makes it easy to chain validations and perform sub-validations for lists or maps. I have an open-source implementation of this written in Golang [1] that I use in all my projects. It enables me to write a form specification and a Go struct and validate as well as coerce unstructured data into the struct. It makes it very easy to validate complex, hierarchical documents like configuration files as well, is easy to extend and provides nice errors.

1: https://github.com/kiprotect/go-helpers/tree/master/forms

Typescript to JSON Schema

For anyone using both TypeScript and JSON schemas, but wanting to use TypeScript as the source of truth, I highly recommend the following library: [ts-json-schema-generator](https://github.com/YousefED/typescript-json-schema).

It does exactly what it says in the box: turns your TypeScript `types` / `interface` into machine-readable JSON schemas.

The library has a few open issues (does not deal well with some edge cases of composing Omit<> on sum types, and does not support dynamic (const) keys), but compared to manually writing JSON schemas, it's been amazing!

There are a bunch of tools to generate JSON-schema from a TS codebase, ie https://github.com/YousefED/typescript-json-schema

Now that cool thing we wanted to do? This library does exactly that!

> For more complex cases I find myself wishing I could just turn Typescript into some kind of schema validation for JSON.

Not sure if this is what you're looking for, and whether it's powerful and expressive enough for your use case, but you can use typescript-json-schema¹ for this, and validate with eg ajv.

¹https://github.com/YousefED/typescript-json-schema

Use https://github.com/YousefED/typescript-json-schema to go from TS -> json schema

For what it's worth, thanks to TypeScript transformers (a feature baked into the compiler), one can create a transformer library that verifies an object is valid for any TypeScript type and conveys that information to the typechecker. And indeed, it's already been made. It allows to parse unknown into a given T. This is nice, because one can generate a JSON schema out of a TS type, for other languages/codebases to integrate safely.

This is why I originally started a project to convert ts to json schema; https://github.com/YousefED/typescript-json-schema (and also check out a good alternative https://github.com/vega/ts-json-schema-generator)

Typescript JSON schema