OpenAPI structures for Go

This library provides Go structures to marshal/unmarshal and reflect OpenAPI Schema documents.

For automated HTTP REST service framework built with this library please check github.com/swaggest/rest.

Features

• Type safe mapping of OpenAPI 3 documents with Go structures generated from schema.
• Type-based reflection of Go structures to OpenAPI 3.0 or 3.1 schema.
• Schema control with field tags
  • json for request bodies and responses in JSON
  • query, path for parameters in URL
  • header, cookie, formData, file for other parameters
  • form acts as query and formData
  • contentType indicates body content type
  • field tags named after JSON Schema/OpenAPI 3 Schema constraints
  • collectionFormat to unpack slices from string
    • csv comma-separated values,
    • ssv space-separated values,
    • pipes pipe-separated values (|),
    • multi ampersand-separated values (&),
    • json additionally to slices unpacks maps and structs,
• Flexible schema control with jsonschema-go

Example

Other examples.

reflector := openapi3.Reflector{}
reflector.Spec = &openapi3.Spec{Openapi: "3.0.3"}
reflector.Spec.Info.
    WithTitle("Things API").
    WithVersion("1.2.3").
    WithDescription("Put something here")

type req struct {
    ID     string `path:"id" example:"XXX-XXXXX"`
    Locale string `query:"locale" pattern:"^[a-z]{2}-[A-Z]{2}$"`
    Title  string `json:"string"`
    Amount uint   `json:"amount"`
    Items  []struct {
        Count uint   `json:"count"`
        Name  string `json:"name"`
    } `json:"items"`
}

type resp struct {
    ID     string `json:"id" example:"XXX-XXXXX"`
    Amount uint   `json:"amount"`
    Items  []struct {
        Count uint   `json:"count"`
        Name  string `json:"name"`
    } `json:"items"`
    UpdatedAt time.Time `json:"updated_at"`
}

putOp, err := reflector.NewOperationContext(http.MethodPut, "/things/{id}")
handleError(err)

putOp.AddReqStructure(new(req))
putOp.AddRespStructure(new(resp), func(cu *openapi.ContentUnit) { cu.HTTPStatus = http.StatusOK })
putOp.AddRespStructure(new([]resp), func(cu *openapi.ContentUnit) { cu.HTTPStatus = http.StatusConflict })

reflector.AddOperation(putOp)

getOp, err := reflector.NewOperationContext(http.MethodGet, "/things/{id}")
handleError(err)

getOp.AddReqStructure(new(req))
getOp.AddRespStructure(new(resp), func(cu *openapi.ContentUnit) { cu.HTTPStatus = http.StatusOK })

reflector.AddOperation(getOp)

schema, err := reflector.Spec.MarshalYAML()
if err != nil {
    log.Fatal(err)
}

fmt.Println(string(schema))

Output:

openapi: 3.0.3
info:
  description: Put something here
  title: Things API
  version: 1.2.3
paths:
  /things/{id}:
    get:
      parameters:
      - in: query
        name: locale
        schema:
          pattern: ^[a-z]{2}-[A-Z]{2}$
          type: string
      - in: path
        name: id
        required: true
        schema:
          example: XXX-XXXXX
          type: string
      responses:
        "200":
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Resp'
          description: OK
    put:
      parameters:
      - in: query
        name: locale
        schema:
          pattern: ^[a-z]{2}-[A-Z]{2}$
          type: string
      - in: path
        name: id
        required: true
        schema:
          example: XXX-XXXXX
          type: string
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Req'
      responses:
        "200":
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Resp'
          description: OK
        "409":
          content:
            application/json:
              schema:
                items:
                  $ref: '#/components/schemas/Resp'
                type: array
          description: Conflict
components:
  schemas:
    Req:
      properties:
        amount:
          minimum: 0
          type: integer
        items:
          items:
            properties:
              count:
                minimum: 0
                type: integer
              name:
                type: string
            type: object
          nullable: true
          type: array
        string:
          type: string
      type: object
    Resp:
      properties:
        amount:
          minimum: 0
          type: integer
        id:
          example: XXX-XXXXX
          type: string
        items:
          items:
            properties:
              count:
                minimum: 0
                type: integer
              name:
                type: string
            type: object
          nullable: true
          type: array
        updated_at:
          format: date-time
          type: string
      type: object