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https://github.com/spider-gazelle/json-schema

Describe crystal-lang JSON serializable types with JSON Schema
https://github.com/spider-gazelle/json-schema

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Describe crystal-lang JSON serializable types with JSON Schema

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# JSON Schema [![CI](https://github.com/spider-gazelle/json-schema/actions/workflows/ci.yml/badge.svg)](https://github.com/spider-gazelle/json-schema/actions/workflows/ci.yml)

A crystal lang tool for converting JSON serialisable class definitions into the [JSON Schema](https://json-schema.org/) representation.

## Installation

```yaml
dependencies:
json-schema:
github: spider-gazelle/json-schema
```

## Usage

basic type support

```crystal

require "json-schema"

String.json_schema #=> {type: "string"}

Int32.json_schema #=> {type: "integer", format: "Int32"}

Float32.json_schema #=> {type: "number", format: "Float32"}

Array(String | Int32).json_schema #=> { type: "array", items: { anyOf: [{type: "integer", format: "Int32"}, {type: "string"}] } }

# Works with enums
enum TestEnum
Option1
Option2
end

TestEnum.json_schema #=> {type: "string", enum: ["option1", "option2"]}

```

json serialisable support is included too, with deeply nested objects etc.

```crystal

require "json-schema"

class MyType
include JSON::Serializable

getter string : String
getter symbol : Symbol?
getter time : Time
getter integer : Int32
getter union_type : String | Int64 | Bool
end

MyType.json_schema

# outputs

{
type: "object",
properties: {
string: {type: "string"},
symbol: {type: "string"},
time: {type: "string", format: "date-time"},
integer: {type: "integer", format: "Int32"},
union_type: {anyOf: [{type: "boolean"}, {type: "integer", format: "Int64"}, {type: "string"}]}
},
required: ["string", "time", "integer", "union_type"]
}

```

You can also customize schema output using the `@[JSON::Field]` annotation

```crystal

require "json-schema"

class MyType
include JSON::Serializable

# The `EpochConverter` here means the JSON value will actually be an integer
# so to avoid the output being `type: "string", format: "date-time"` you can
# supply a type override and custom format string.
@[JSON::Field(converter: Time::EpochConverter, type: "integer", format: "Int64")]
getter time : Time

# or if you just want to provide a custom format
@[JSON::Field(format: "email")]
getter email : String
end

```

for anything too confusing it falls back to a generic `{ type: "object" }` however this should only happen in some cases where you've inherited generic objects. e.g. `class Me < Hash(String, Int32)` (although this case is handled correctly)