Revert "README: warn on prefer-method: link TNS-23"

This reverts commit 57e5658.

This commit was a mistake: it included work-in-progess development
which was not ready for release. Only the README change should have
been included.

README.md

@@ -453,15 +453,6 @@ To avoid this problem, always create new instances of records after a
 refresh.
 
 
-### Warnings for Multimethods
-
-Calling `prefer-method` is a global side-effect. If you modify a call
-to `prefer-method` and reload the namespace containing it, Clojure may
-throw "java.lang.IllegalStateException: Preference conflict in multimethod."
-The workaround is to call `remove-method` before reloading.
-tools.namespace cannot detect this situation automatically. See [TNS-23].
-
-
 
 Change Log
 ----------------------------------------
@@ -568,10 +559,6 @@ Change Log
 [TNS-17]: http://dev.clojure.org/jira/browse/TNS-17
 [TNS-18]: http://dev.clojure.org/jira/browse/TNS-18
 [TNS-19]: http://dev.clojure.org/jira/browse/TNS-19
-[TNS-20]: http://dev.clojure.org/jira/browse/TNS-20
-[TNS-21]: http://dev.clojure.org/jira/browse/TNS-21
-[TNS-22]: http://dev.clojure.org/jira/browse/TNS-22
-[TNS-23]: http://dev.clojure.org/jira/browse/TNS-23
 [java.classpath]: https://github.com/clojure/java.classpath
 
 

src/main/clojure/clojure/tools/namespace/dir.clj

@@ -35,7 +35,7 @@
   (let [now (System/currentTimeMillis)]
     (-> tracker
         (update-in [::files] #(if % (apply disj % deleted) #{}))
-        (file/remove-files (into deleted modified))
+        (file/remove-files deleted)
         (update-in [::files] into modified)
         (file/add-files modified)
         (assoc ::time now))))

src/main/clojure/clojure/tools/namespace/file.clj

@@ -42,16 +42,14 @@
               m))
           {} files))
 
-(def ^:private merge-map (fnil merge {}))
-
 (defn add-files
   "Reads ns declarations from files; returns an updated dependency
   tracker with those files added."
   [tracker files]
   (let [{:keys [depmap filemap]} (files-and-deps files)]
     (-> tracker
         (track/add depmap)
-        (update-in [::filemap] merge-map filemap))))
+        (update-in [::filemap] (fnil merge {}) filemap))))
 
 (defn remove-files
   "Returns an updated dependency tracker with files removed. The files

src/main/clojure/clojure/tools/namespace/reload.clj

@@ -34,10 +34,6 @@
         (let [n (first load)]
           (try (require n :reload)
                (update-in tracker [::track/load] rest)
-               ;; This doesn't work because we don't ever try to reload the file.
-               ;; (catch java.io.FileNotFoundException e
-               ;;   (assoc tracker
-               ;;     ::error e ::error-ns n ::track/load (rest load)))
                (catch Throwable t
                  (assoc tracker
                    ::error t ::error-ns n ::track/unload load))))