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(require '[spec-tools.swagger.core :as swagger])

An utility to transform Specs to Swagger2 Schemas.

Spec transformations

swagger/transform converts specs into Swagger2 Schema. Transformation can be customized with the following optional options:

  • :type - a target type, either :parameter (Parameter Object) or :schema (Schema Object). If value is not defined, :schema is used.
  • :in - a parameter subtype, which is one of: :query, :header, :path, :body or :formData. See Parameter Object for details.

NOTE: As clojure.spec is more powerful than the Swagger2 Schema, we are losing some data in the transformation. We try to retain all the information using vendor extensions.

(swagger/transform float?)
; {:type "number" :format "float"}

;; no "null" in swagger2
(swagger/transform (s/nilable string?))
; {:type "string", :x-nullable true}

;; swagger2 parameter syntax
(swagger/transform (s/nilable string?) {:type :parameter})
; {:type "string", :allowEmptyValue true}

;; no "anyOf" in swagger2
(swagger/transform (s/cat :int integer? :string string?))
; {:type "array"
;  :items {:type "integer"
;          :x-anyOf [{:type "integer"}
;                    {:type "string"}]}}

Annotated Specs

Specs can be annotated to populate the JSON Schemas.

  • :name is copied into :title
  • :description is used as-is
  • all keys with namespace json-schema and swagger are used without the namespace
(require '[spec-tools.core :as st])

    {:spec integer?
     :name "integer"
     :description "it's an int"
     :swagger/example 42
     :json-schema/default 42}))
;{:type "integer"
; :title "integer"
; :description "it's an int"
; :example 42
; :default 42}

Swagger Spec generation

swagger/swagger-spec function takes an extended swagger2 spec as map and transforms it into a valid Swagger Object. Rules:

  • by default, data is passed through, allowing any valid swagger data to be used
  • for qualified map keys, swagger/expand multimethod is invoked with the key, value and the map as arguments
    • dispatches on the key, defaulting to ::swagger/extension
    • returns a map that get's merged in to original map, without the dispatched key

Predefined dispatch keys below.


Value should be a map with optional keys :body, :query, :path, :header and :formData. For all but :body, the value should be a s/keys spec (describing the ring parameters). With :body, the value can be any clojure.spec.alpha/Spec.

Returns a map with key :parameters with value of vector of swagger Parameter Objects, merged over the existing :parameters. Duplicate parameters (with identical :in and :name are overridden)

(require '[clojure.spec.alpha :as s])

(s/def ::id string?)
(s/def ::name string?)
(s/def ::street string?)
(s/def ::city #{:tre :hki})
(s/def ::address (s/keys :req-un [::street ::city]))
(s/def ::user (s/keys :req-un [::id ::name ::address]))

      [;; existing parameter, will be overriddden
       {:in "query"
        :name "name"
        :required false}
       ;; unique parameter, will remain
       {:in "query"
        :name "name2"
        :type "string"
        :required true}]
      ;; the spec-parameters
      {:query (s/keys :opt-un [::name])
       :body ::user}}}}})
; {"echo"
;  {:post
;   {:parameters [{:in "query"
;                  :name "name2"
;                  :type "string"
;                  :required true}
;                 {:in "query"
;                  :name "name"
;                  :description ""
;                  :type "string"
;                  :required false}
;                 {:in "body",
;                  :name "user/user",
;                  :description "",
;                  :required true,
;                  :schema {:type "object",
;                           :properties {"id" {:type "string"},
;                                        "name" {:type "string"},
;                                        "address" {:type "object",
;                                                   :properties {"street" {:type "string"},
;                                                                "city" {:enum [:tre :hki],
;                                                                        :type "string"}},
;                                                   :required ["street" "city"],
;                                                   :title "user/address"}},
;                           :required ["id" "name" "address"],
;                           :title "user/user"}}]}}}}


Value should a Swagger2 Responses Definition Object with Spec or Spec as the :schema. Returns a map with key :responses with :schemas transformed into Swagger2 Schema Objects, merged over existing :responses.

  {:responses {404 {:description "fail"}
               500 {:description "fail"}}
   ::swagger/responses {200 {:schema ::user
                             :description "Found it!"}
                        404 {:description "Ohnoes."}}})
;{:responses {404 {:description "Ohnoes."}
;             500 {:description "fail"}
;             200 {:schema {:type "object"
;                           :properties {"id" {:type "string"}
;                                        "name" {:type "string"}
;                                        "address" {:type "object"
;                                                   :properties {"street" {:type "string"}
;                                                                "city" {:type "string"
;                                                                        :enum [:tre :hki]}}
;                                                   :required ["street" "city"]
;                                                   :title "user/address"}}
;                           :required ["id" "name" "address"]
;                           :title "user/user"}
;                  :description "Found it!"}}}

Full example

(require '[spec-tools.swagger.core :as swagger])
(require '[clojure.spec.alpha :as s])

(s/def ::id string?)
(s/def ::name string?)
(s/def ::street string?)
(s/def ::city #{:tre :hki})
(s/def ::address (s/keys :req-un [::street ::city]))
(s/def ::user (s/keys :req-un [::id ::name ::address]))

  {:swagger "2.0"
   :info {:version "1.0.0"
          :title "Sausages"
          :description "Sausage description"
          :termsOfService ""
          :contact {:name "My API Team"
                    :email ""
                    :url ""}
          :license {:name "Eclipse Public License"
                    :url ""}}
   :tags [{:name "user"
           :description "User stuff"}]
   :paths {"/api/ping" {:get {:responses {:default {:description ""}}}}
           "/user/:id" {:post {:summary "User Api"
                               :description "User Api description"
                               :tags ["user"]
                               ::swagger/parameters {:path (s/keys :req [::id])
                                                     :body ::user}
                               ::swagger/responses {200 {:schema ::user
                                                         :description "Found it!"}
                                                    404 {:description "Ohnoes."}}}}}})
;{:swagger "2.0"
; :info {:version "1.0.0"
;        :title "Sausages"
;        :description "Sausage description"
;        :termsOfService ""
;        :contact {:name "My API Team" :email "" :url ""}
;        :license {:name "Eclipse Public License" :url ""}}
; :tags [{:name "user" :description "User stuff"}]
; :paths {"/api/ping" {:get {:responses {:default {:description ""}}}}
;         "/user/:id" {:post
;                      {:summary "User Api"
;                       :description "User Api description"
;                       :tags ["user"]
;                       :parameters [{:in "path"
;                                     :name "user/id"
;                                     :description ""
;                                     :type "string"
;                                     :required true}
;                                    {:in "body"
;                                     :name "user/user"
;                                     :description ""
;                                     :required true
;                                     :schema {:type "object"
;                                              :properties {"id" {:type "string"}
;                                                           "name" {:type "string"}
;                                                           "address" {:type "object"
;                                                                      :properties {"street" {:type "string"}
;                                                                                   "city" {:type "string"
;                                                                                           :enum [:tre :hki]}}
;                                                                      :required ["street" "city"]
;                                                                      :title "user/address"}}
;                                              :required ["id" "name" "address"]
;                                              :title "user/user"}}]
;                       :responses {200 {:schema {:type "object"
;                                                 :properties {"id" {:type "string"}
;                                                              "name" {:type "string"}
;                                                              "address" {:type "object"
;                                                                         :properties {"street" {:type "string"}
;                                                                                      "city" {:enum [:tre :hki]
;                                                                                              :type "string"}}
;                                                                         :required ["street" "city"]
;                                                                         :title "user/address"}}
;                                                 :required ["id" "name" "address"]
;                                                 :title "user/user"}
;                                        :description "Found it!"}
;                                   404 {:description "Ohnoes."}}}}}}

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