First part of #49 -- allow :config :render-types to override

Doesn't provide runtime variable rendering but it allows additional
render types to be added as well as overriding existing ones. Documents
`render-data` to make this "supported" (required for custom types).

README.md

@@ -119,6 +119,7 @@ Any controller function also has access to the the FW/1 API (after `require`ing
 * `(redirecting? rc)` - returns `true` if the current request will redirect, i.e., `(redirect rc ...)` has been called.
 * `(reload? rc)` - returns `true` if the current request includes URL parameters to force an application reload.
 * `(remote-addr rc)` - returns the IP address of the remote requestor (if available). Checks the `"x-forwarded-for"` header (set by load balancers) then Ring's `:remote-addr` field.
+* `(render-data rc type data)` or `(render rc status type data)` - low-level function to tell FW/1 to render the specified `data` as the specified `type`, optionally with the specified `status` code. Prefer the `render-xxx` convenience functions that follow is you are rendering standard data types.
 * `(render-xxx rc data)` or `(render-xxx rc status data)` - render the specified `data`, optionally with the specified `status` code, in format _xxx_: `html`, `json`, `raw-json`, `text`, `xml`.
 * `(rendering? rc)` - returns `true` if the current request will render data (instead of a page), i.e., `(render-xxx rc ...)` has been called.
 * `(ring rc)` - returns the original Ring request.
@@ -163,6 +164,7 @@ as a map (preferred) or as an arbitrary number of inline key / value pairs (lega
 * `:password` - specify a password for the application reload URL flag, default `"secret"` - see also `:reload`.
 * `:reload` - specify an `rc` key for the application reload URL flag, default `:reload` - see also `:password`.
 * `:reload-application-on-every-request` - boolean, whether to reload controller, view and layout components on every request (intended for development of applications).
+* `:render-types` - an optional map of data types to replace or augment the built-in data rendering. For each data type (keyword), the value is a map of `:type` (the `Content-Type` to return) and `:body` processing function. Each function takes two arguments: the FW/1 configuration and the data to render. By default, the `:html`, `:raw-json`, and `:text` data types have a `:body` function that just returns the `data` argument as-is.
 * `:routes` - a vector of hash maps, specifying route patterns and what to map them to (full documentation coming in due course).
 * `:selmer-tags` - you can specify a map that is passed to the Selmer parser to override what characters are used to identify tags, filters
 * `:suffix` - the file extension used for views and layouts. Default is `"html"`.

src/framework/one.clj

@@ -38,13 +38,6 @@
                (meta #'selmer.filters/add-filter!))
         (deref #'selmer.filters/add-filter!))
 
-;; render data support
-(defn render-data
-  ([rc as expr]
-   (assoc rc ::render {:as as :data expr}))
-  ([rc status as expr]
-   (assoc rc ::render {:status status :as as :data expr})))
-
 ;; FW/1 base functionality - this is essentially the public API of the
 ;; framework with the entry point to create Ring middleware being:
 ;; (fw1/default-handler) - returns Ring middleware for your application
@@ -125,6 +118,15 @@
   (or (get-in rc [::ring :headers "x-forwarded-for"])
       (get-in rc [::ring :remote-addr])))
 
+(defn render-data
+  "Tell FW/1 to render this expression as the given type.
+  Prefer the convenience functions below, unless you are rendering
+  custom data types."
+  ([rc as expr]
+   (assoc rc ::render {:as as :data expr}))
+  ([rc status as expr]
+   (assoc rc ::render {:status status :as as :data expr})))
+
 (defn render-html
   "Tell FW/1 to render this expression (string) as-is as HTML."
   ([rc expr]
@@ -354,7 +356,7 @@
   content type and the data rendered as the body."
   [config {:keys [status as data]
            :or   {status 200}}]
-  (let [renderer (render-types as)]
+  (let [renderer ((merge render-types (:render-types config)) as)]
     {:status  status
      :headers {"Content-Type" (:type renderer)}
      :body    ((:body renderer) config data)}))