This page is for the current v1 alpha version of Schemars. This version is still under development, and further breaking changes may be introduced.

To view this page for the current stable release of Schemars (v0.8.x), click here.

Using Serde Attributes

One of the main aims of this library is compatibility with Serde. Any generated schema should match how serde_json would serialize/deserialize to/from JSON. To support this, Schemars will check for any #[serde(...)] attributes on types that derive JsonSchema, and adjust the generated schema accordingly.

The list of supported #[serde] attributes are documented here.

use schemars::{schema_for, JsonSchema};
use serde::{Deserialize, Serialize};

#[derive(Deserialize, Serialize, JsonSchema)]
#[serde(rename_all = "camelCase", deny_unknown_fields)]
pub struct MyStruct {
    #[serde(rename = "myNumber")]
    pub my_int: i32,
    pub my_bool: bool,
    #[serde(default)]
    pub my_nullable_enum: Option<MyEnum>,
}

#[derive(Deserialize, Serialize, JsonSchema)]
#[serde(untagged)]
pub enum MyEnum {
    StringNewType(String),
    StructVariant { floats: Vec<f32> },
}

fn main() {
    let schema = schema_for!(MyStruct);
    println!("{}", serde_json::to_string_pretty(&schema).unwrap());
}

Click to see the output JSON schema...

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "MyStruct",
  "type": "object",
  "properties": {
    "myBool": {
      "type": "boolean"
    },
    "myNullableEnum": {
      "anyOf": [
        {
          "$ref": "#/$defs/MyEnum"
        },
        {
          "type": "null"
        }
      ],
      "default": null
    },
    "myNumber": {
      "type": "integer",
      "format": "int32"
    }
  },
  "additionalProperties": false,
  "required": [
    "myNumber",
    "myBool"
  ],
  "$defs": {
    "MyEnum": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "object",
          "properties": {
            "floats": {
              "type": "array",
              "items": {
                "type": "number",
                "format": "float"
              }
            }
          },
          "required": [
            "floats"
          ]
        }
      ]
    }
  }
}