reitit/doc/coercion/data_spec_coercion.md

# Data-spec Coercion

[Data-specs](https://github.com/metosin/spec-tools#data-specs) is alternative, macro-free syntax to define `clojure.spec`s. As a bonus, supports the [runtime transformations via conforming](https://clojure.atlassian.net/browse/CLJ-2116) out-of-the-box.

```clj
(require '[reitit.coercion.spec])
(require '[reitit.coercion :as coercion])
(require '[reitit.core :as r])

(def router
  (r/router
    ["/:company/users/:user-id" {:name ::user-view
                                 :coercion reitit.coercion.spec/coercion
                                 :parameters {:path {:company string?
                                                     :user-id int?}}}]
    {:compile coercion/compile-request-coercers}))

(defn match-by-path-and-coerce! [path]
  (if-let [match (r/match-by-path router path)]
    (assoc match :parameters (coercion/coerce! match))))
```

Successful coercion:

```clj
(match-by-path-and-coerce! "/metosin/users/123")
; #Match{:template "/:company/users/:user-id",
;        :data {:name :user/user-view,
;               :coercion <<:spec>>
;               :parameters {:path {:company string?,
;                                   :user-id int?}}},
;        :result {:path #object[reitit.coercion$request_coercer$]},
;        :path-params {:company "metosin", :user-id "123"},
;        :parameters {:path {:company "metosin", :user-id 123}}
;        :path "/metosin/users/123"}
```

Failing coercion:

```clj
(match-by-path-and-coerce! "/metosin/users/ikitommi")
; => ExceptionInfo Request coercion failed...
```