Add support for ns-unalias (#796)

src/sci/impl/namespaces.cljc

@@ -568,6 +568,12 @@
                                 :else the-ns-map))))))
   nil)
 
+(defn sci-ns-unalias [ctx sci-ns sym]
+  (swap! (:env ctx)
+    (fn [env]
+      (update-in env [:namespaces (sci-ns-name (sci-the-ns ctx sci-ns)) :aliases] dissoc sym)))
+  nil)
+
 (defn sci-all-ns [ctx]
   (let [env (:env ctx)
         namespaces (get @env :namespaces)
@@ -1322,6 +1328,7 @@
    'ns-refers (core-var 'ns-refers sci-ns-refers true)
    'ns-map (core-var 'ns-map sci-ns-map true)
    'ns-unmap (core-var 'ns-unmap sci-ns-unmap true)
+   'ns-unalias (core-var 'ns-unalias sci-ns-unalias true)
    'ns-name (core-var 'ns-name sci-ns-name)
    'odd? (copy-core-var odd?)
    #?@(:cljs ['object? (copy-core-var object?)])

test/sci/namespaces_test.cljc

@@ -219,6 +219,19 @@
 (deftest remove-ns-test
   (is (nil? (eval* "(ns foo) (ns bar) (remove-ns 'foo) (find-ns 'foo)"))))
 
+(deftest ns-unalias-test
+  (testing "Removing an alias in an unknown namespace throws"
+    (is (thrown? #?(:clj Exception :cljs js/Error) (eval* "(ns-unalias (find-ns 'unknown) 'core)"))))
+
+  (testing "Removing an undefined alias is a no-op"
+    (is (nil? (eval* "(ns-unalias *ns* 'core)"))))
+
+  (testing "Removing a defined alias -- ns symbol"
+    (is (nil? (eval* "(alias 'core 'clojure.core) (ns-unalias 'user 'core) (get (ns-aliases *ns*) 'core)"))))
+
+  (testing "Removing a defined alias -- ns object"
+    (is (nil? (eval* "(alias 'core 'clojure.core) (ns-unalias *ns* 'core) (get (ns-aliases *ns*) 'core)")))))
+
 (deftest ns-syntax-test
   (is (thrown-with-msg?
        #?(:clj Exception :cljs js/Error)