Merge pull request #336 from Sohalt/master

enforce reg-sub :<- syntax

CHANGES.md

@@ -1,5 +1,9 @@
 ## Unreleased
 
+#### Breaking
+
+- - `reg-sub` enforces using `:<-` to indicate subscription inputs. Previously any keyword would have worked here. While using anything other than `:<-` was undefined behaviour previously, this could possibly break some code when upgrading. Thanks to [@Sohalt](https://github.com/Sohalt) [#336](https://github.com/Day8/re-frame/pull/336).
+
 #### Fixes
 
 - `re-frame.interceptor/update-coeffect` has been fixed. [#328](https://github.com/Day8/re-frame/pull/328)

src/re_frame/subs.cljc

@@ -183,14 +183,18 @@
                              f)
 
                          ;; one sugar pair
-                         2 (fn inp-fn
-                             ([_] (subscribe (second input-args)))
-                             ([_ _] (subscribe (second input-args))))
+                         2 (let [[marker vec] input-args]
+                             (when-not (= :<- marker)
+                               (console :error err-header "expected :<-, got:" marker))
+                             (fn inp-fn
+                               ([_] (subscribe vec))
+                               ([_ _] (subscribe vec))))
 
                          ;; multiple sugar pairs
-                         (let [pairs (partition 2 input-args)
-                               vecs  (map last pairs)]
-                           (when-not (every? vector? vecs)
+                         (let [pairs   (partition 2 input-args)
+                               markers (map first pairs)
+                               vecs    (map last pairs)]
+                           (when-not (and (every? #{:<-} markers) (every? vector? vecs))
                              (console :error err-header "expected pairs of :<- and vectors, got:" pairs))
                            (fn inp-fn
                              ([_] (map subscribe vecs))