@gcornut/valibot-json-schema v0.0.28
@gcornut/valibot-json-schema
CLI and JS utility to convert valibot schemas to JSON schema (draft 07).
Some of the features of Valibot can't be converted to JSON schema. JS-specific types like blob
or nan
obviously
can't have an equivalent.
See supported features for more info.
Command Line Tool
This lib exports a CLI that can be used to quickly convert JS modules defining valibot schemas into a JSON schema.
# Convert valibot schemas to JSON schema
npx @gcornut/valibot-json-schema to-json-schema ./schemas.js
This outputs a conversion of the Valibot schemas into JSON schema. If the default export is a Valibot schemas, it is used as the root definition. Other exported Valibot schemas are converted in the JSON schema definitions section.
Input file ./schemas.js
:
import * as v from 'valibot';
export const AString = v.string();
const AnObject = v.object({ aString: AString });
export default AnObject;
Output conversion:
{
"$schema": "http://json-schema.org/draft-07/schema#",
"definitions": {
"AString": {
"type": "string"
}
},
"properties": {
"aString": {
"$ref": "#/definitions/AString"
}
},
"required": [
"aString"
],
"type": "object"
}
AnObject
is the default export in the source module, so it is converted as the root definition. AString
is exported
separately, so it is exported to the definitions
section.
ESM and TypeScript input module
The valibot-json-schema
CLI loads the input JS module using standard NodeJS CommonJS require. This means you will
have issues with ESM or TypeScript modules.
To remedy that, you will either have to preinstall ebuild-runner
and esbuild
(so that the program can use them) or
use a Node-compatible runtime that support these modules (ex: bun, replacing npx
with bunx
).
Example:
# Convert from TS/ESM module using bunx
bunx @gcornut/valibot-json-schema to-json-schema ./schemas.ts
# Convert from TS/ESM module with esbuild-runner preinstalled
npm install esbuild esbuild-runner
npx @gcornut/valibot-json-schema to-json-schema ./schemas.ts
# Convert from TS/ESM module using `yarn dlx` multi-package feature
yarn dlx -p esbuild -p esbuild-runner -p @gcornut/valibot-json-schema valibot-json-schema to-json-schema ./schemas.ts
CLI parameters
Use -o <file>
option to output the JSON schema to a file instead of stdout
.
Use -t <type>
option to select the root definitions from the module exports (defaults to the "default" export).
Example: -t foo.bar
will get the property bar
on the foo
export of the input JS module.
Use -d <type>
option to select the definitions from the module exports (instead of using all non-default export).
Example: -d foo.bar
will get the property bar
on the foo
export of the input JS module.
See Advanced options for more options.
Programmatic usage
Use the toJSONSchema
function to convert a Valibot schema into JSON schema (v7):
import { toJSONSchema } from '@gcornut/valibot-json-schema';
import { string } from 'valibot';
toJSONSchema({ schema: string() })
// {
// $schema: 'http://json-schema.org/draft-07/schema#',
// type: 'string',
// }
If you have many named schemas to convert, you can use the definitions
option schema to list as a plain object so that
both the schema names (object keys) and schema definitions (object values) are exported to JSON schema.
import { toJSONSchema } from '@gcornut/valibot-json-schema';
import { number } from 'valibot';
const Number = number();
toJSONSchema({ definitions: { Number } });
// {
// $schema: 'http://json-schema.org/draft-07/schema#',
// definitions: { Number: { type: 'number' } },
// }
See Advanced options for more options.
Advanced options
Strict object types
Using the strictObjectTypes
option (--strictObjectTypes
in the CLI), you can force all object type block unknown
keys (additionalProperties: false
).
Ignore unknown validation
You might want to have advanced validation in your valibot schema that JSON schema can't support (
like custom()). By default, toJSONSchema()
will throw an error to let you know
these can't be converted to JSON schema.
Using the ignoreUnknownValidation
option (--ignoreUnknownValidation
in the CLI), you can ignore unsupported valibot
validations.
Common type strategies
Many JS types don't have a direct equivalent in JSON and toJSONSchema()
will throw an error when encountering any of
those. However, some of these types have common strategies to convert them.
Using the dateStrategy
option (--dateStrategy
in the CLI), you can choose to convert JS Date objects into a string (
with the date-time
format) or into an integer (with the unix-time
format).
Using the undefinedStrategy
option (--undefinedStrategy
in the CLI), you can choose to convert undefined
to the "
any" schema (no validation) or to the null
type.
Using the bigintStrategy
option (--bigintStrategy
in the CLI), you can choose to convert JS BigInt values to an
integer (with the int64
format) or into a string.
Custom schema conversion
In some cases, you might want to provide custom schema conversion to override standard schema conversion or to add conversion of unsupported schemas.
Using the customSchemaConversion
option, you can provide a custom schema converted for any valibot schema type.
Example: converting JS Set schema into an array schema
import { SetSchema } from 'valibot';
toJSONSchema({
schema: set(string()),
customSchemaConversion: {
// Treat set type like an array
set: (schema, converter) => converter(array((schema as SetSchema<any>).value))
},
})
// => { type: 'array', items: { type: 'string' } }
Supported features
Some converted schema might have slightly different behavior in a JSON schema validator, especially on string
formats (email
, ipv4
, date
, etc.) since their implementation is different from valibot implementation.
Here is the list of supported Valibot features (some have partial support):
feature | status |
---|---|
any schema | ✅ supported |
null schema | ✅ supported |
number schema | ✅ supported |
bigint schema | ⚠️ with bigintStrategy option provided |
string schema | ✅ supported |
boolean schema | ✅ supported |
literal schema | ⚠️ partial: only JSON-compatible literal are supported |
nullable schema | ✅ supported |
nullish schema | ✅ supported |
optional schema | ✅ supported |
never schema | ⚠️ partial: only inside object rest or tuple rest params |
picklist schema | ⚠️ partial: only JSON-compatible literal are supported |
enum_ schema | ✅ supported |
union schema | ✅ supported |
variant schema | ⚠️ partial: converted just like an union |
intersect schema | ✅ supported |
array schema | ✅ supported |
tuple schema | ✅ supported |
object schema | ✅ supported |
record schema | ⚠️ partial: only string key are allowed, applicable to plain object only, not arrays |
lazy schema (previously named recursive ) | ⚠️ partial: only if the schema inside is referenced in definitions |
date schema | ⚠️ with dateStrategy option provided |
length validation | ✅ supported |
maxLength validation | ✅ supported |
minLength validation | ✅ supported |
regex validation | ⚠️ partial: only on RegExp features supported by JSON schema |
value validation | ⚠️ partial: only on string , number and boolean |
minValue validation | ⚠️ partial: only on number |
maxValue validation | ⚠️ partial: only on number |
multipleOf validation | ✅ supported |
integer validation | ✅ supported |
email validation | ✅ supported (JSON schema format) |
isoDate validation | ✅ supported (JSON schema format) |
isoTimestamp validation | ✅ supported (JSON schema format) |
ipv4 validation | ✅ supported (JSON schema format) |
ipv6 validation | ✅ supported (JSON schema format) |
uuid validation | ✅ supported (JSON schema format) |
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