From cf8dd5afbf9963d0ed712b7e92928bce140ff3dd Mon Sep 17 00:00:00 2001
From: yuhan0 <qythium@gmail.com>
Date: Tue, 3 Mar 2020 16:29:07 +0800
Subject: [PATCH] Extend undef op to work on fully qualified symbols (#670)

---
 CHANGELOG.md                                  |  2 +
 src/cider/nrepl/middleware/undef.clj          | 23 +++++++++--
 .../clj/cider/nrepl/middleware/undef_test.clj | 38 ++++++++++++++++++-
 3 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6adc2a117..4bad4372d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@
 
 ### New Features
 
+* [#670](https://github.com/clojure-emacs/cider-nrepl/pull/670): Extend undef op to work on fully qualified symbols.
+
 ## 0.24.0 (2020-02-14)
 
 ### Bugs fixed
diff --git a/src/cider/nrepl/middleware/undef.clj b/src/cider/nrepl/middleware/undef.clj
index fc839e8b5..5d061649a 100644
--- a/src/cider/nrepl/middleware/undef.clj
+++ b/src/cider/nrepl/middleware/undef.clj
@@ -1,14 +1,29 @@
 (ns cider.nrepl.middleware.undef
-  "Undefine a symbol"
+  "Middleware for undefining symbols.
+  Fully qualified symbols are interpreted as a var to be unmapped in its
+  original namespace, whereas unqualified symbols are interpreted as both a var
+  and ns alias to be unmapped from the current namespace."
   (:require
    [cider.nrepl.middleware.util.error-handling :refer [with-safe-transport]]
    [orchard.misc :as misc]))
 
 (defn undef
+  "Undefines a symbol.
+  When `symbol` is unqualified, it is interpreted as both an alias and var to be
+  unmapped from the namespace `ns`.
+  When qualified (eg. `foo/bar`), it is interpreted as a var to be unmapped in
+  the namespace `foo`, which may be an alias in `ns`."
   [{:keys [ns symbol]}]
-  (let [[ns symbol] (map misc/as-sym [ns symbol])]
-    (ns-unalias ns symbol)
-    (ns-unmap ns symbol)
+  (let [ns (misc/as-sym ns)
+        [sym-ns sym-name] ((juxt (comp misc/as-sym namespace) misc/name-sym)
+                           (misc/as-sym symbol))]
+    (if sym-ns
+      ;; fully qualified => var in other namespace
+      (let [other-ns (get (ns-aliases ns) sym-ns sym-ns)]
+        (ns-unmap other-ns sym-name))
+      ;; unqualified => alias or var in current ns
+      (do (ns-unalias ns sym-name)
+          (ns-unmap ns sym-name)))
     symbol))
 
 (defn undef-reply
diff --git a/test/clj/cider/nrepl/middleware/undef_test.clj b/test/clj/cider/nrepl/middleware/undef_test.clj
index 9c078bf92..c32eddbf4 100644
--- a/test/clj/cider/nrepl/middleware/undef_test.clj
+++ b/test/clj/cider/nrepl/middleware/undef_test.clj
@@ -19,7 +19,43 @@
                                       :symbol "x"}))))
     (is (= ["nil"]
            (:value (session/message {:op "eval"
-                                     :code "(ns-resolve 'user 'x)"}))))))
+                                     :code "(ns-resolve 'user 'x)"})))))
+  (testing "undef undefines vars in other namespaces"
+    (is (= #{"done"}
+           (:status (session/message {:op   "eval"
+                                      :code "(do (ns other.ns) (in-ns 'user) (require '[other.ns :as other]))"}))))
+    (is (= ["#'other.ns/x"]
+           (:value (session/message {:op   "eval"
+                                     :code "(do (in-ns 'other.ns) (def x 1) (in-ns 'user) (ns-resolve 'other.ns 'x))"}))))
+    (is (= #{"done"}
+           (:status (session/message {:op     "undef"
+                                      :ns     "other.ns"
+                                      :symbol "x"}))))
+    (is (= ["nil"]
+           (:value (session/message {:op "eval"
+                                     :code "(ns-resolve 'other.ns 'x)"})))))
+  (testing "undef takes fully qualified symbols"
+    (is (= ["#'other.ns/x"]
+           (:value (session/message {:op   "eval"
+                                     :code "(do (in-ns 'other.ns) (def x 1) (in-ns 'user) (ns-resolve 'other.ns 'x))"}))))
+    (is (= #{"done"}
+           (:status (session/message {:op     "undef"
+                                      :ns     "user"
+                                      :symbol "other.ns/x"}))))
+    (is (= ["nil"]
+           (:value (session/message {:op "eval"
+                                     :code "(ns-resolve 'other.ns 'x)"})))))
+  (testing "undef resolves namespace aliases in fully qualified symbols"
+    (is (= ["#'other.ns/x"]
+           (:value (session/message {:op   "eval"
+                                     :code "(do (in-ns 'other.ns) (def x 1) (in-ns 'user) (ns-resolve 'other.ns 'x))"}))))
+    (is (= #{"done"}
+           (:status (session/message {:op     "undef"
+                                      :ns     "user"
+                                      :symbol "other/x"}))))
+    (is (= ["nil"]
+           (:value (session/message {:op "eval"
+                                     :code "(ns-resolve 'other.ns 'x)"}))))))
 
 (deftest undef-alias-test
   (testing "undef undefines aliases"