openapi_type

This crate gives static type information for primitives and commonly used types from the standard library and other commonly used libraries (see features) when the according feature is enabled. Please refer to the Cargo.toml for a list of all available feature flags and optional dependencies. Also, it provides a derive macro for structs and enums to gain access to their static type information at runtime.

The core of this crate is the OpenapiType trait. It has three static function, where schema, which returns an OpenapiSchema, is the one you are probably looking for. It assembles the static type information in a way that is convenient to use for a generated OpenAPI specification, but can also be utilized in other use cases as well.

Custom Types

To gain access to the static type information of your custom types at runtime, the easiest way is to use the derive macro:

#[derive(OpenapiType)]
struct FooBar {
	foo: Option<String>,
	bar: u64
}

OpenAPI specification

Using above type, running FooBar::schema().into_schema() yields

properties:
  foo:
    type: string
  bar:
    type: integer
    minimum: 0
    format: int64
type: object
required:
  - bar
title: FooBar

Note, however, that this is not sufficient for more complex types. If one of your structs fields is a type that has a name (that is, Type::schema().name is not None), above schema will contain a reference to that schema. Therefore, always remember to put the dependencies into the specification alongside the type you are interested in.

Path Parameters

We can also treat the FooBar struct from above as a struct containing path parameters, if we construct an Operation for a path like /foo/{foo}/bar/{bar}. Running FooBar::path_params() yields

- name: foo
  in: path
  required: true
  schema:
    type:
      - string
      - "null"
- name: bar
  in: path
  required: true
  schema:
    type: integer
    minimum: 0
    format: int64

Query Parameters

Likewise, we can treat the FooBar struct from above as a struct containing query parameters. Running FooBar::query_params() yields

- name: foo
  in: query
  required: false
  allowEmptyValue: true
  schema:
    type: string
- name: bar
  in: query
  required: true
  schema:
    type: integer
    minimum: 0
    format: int64

Features

The following cargo features may be enabled for this crate to unlock additional implementations for larger tuples. For example, the tuples32 feature would unlock the implementation for tuples with sizes up to 32.

• tuples16 (enabled by default)
• tuples32
• tuples48
• tuples64

The following cargo features may be enabled for this crate to unlock additional implementations for external crates:

• chrono: Enable all of the below:
  • chrono04: Enable implementations for chrono 0.4
• hashbrown: Enable all of the below:
  • hashbrown016: Enable implementations for hashbrown 0.16
  • hashbrown017: Enable implementations for hashbrown 0.17
• jiff: Enable all of the below:
  • jiff02: Enable implementations for jiff 0.2
• linked-hash-map: Enable all of the below:
  • linked-hash-map05: Enable implementations for linked-hash-map 0.5
• time: Enable all of the below:
  • time03: Enable implementations for time 0.3
• url: Enable all of the below:
  • url2: Enable implementations for url 2.x
• uuid: Enable all of the below:
  • uuid1: Enable implementations for uuid 1.x

Note that support for indexmap 2.x is enabled by default.

Versioning

Like all rust crates, this crate will follow semantic versioning guidelines. However, changing the MSRV (minimum supported rust version) is not considered a breaking change.

License

Copyright (C) 2021-2026 Dominic Meiser and contributors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

	https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.