CLJS-2654: Gracefully handle browser launch failure

Author: mfikes

src/main/clojure/cljs/repl/browser.clj

@@ -290,6 +290,23 @@
 
 (def lock (Object.))
 
+(defn- waiting-to-connect-message [url]
+  (print-str "Waiting for browser to connect to" url "..."))
+
+(defn- maybe-browse-url [base-url]
+  (try
+    (browse/browse-url (str base-url "?rel=" (System/currentTimeMillis)))
+    (catch Throwable t
+      (if-some [error-message (not-empty (.getMessage t))]
+        (println "Failed to launch a browser:\n" error-message "\n")
+        (println "Could not launch a browser.\n"))
+      (println "You can instead launch a non-browser REPL (Node or Nashorn).\n")
+      (println "You can disable automatic browser launch with this REPL option")
+      (println "  :launch-browser false")
+      (println "and you can specify the listen IP address with this REPL option")
+      (println "  :host \"127.0.0.1\"\n")
+      (println (waiting-to-connect-message base-url)))))
+
 (defn setup [{:keys [working-dir launch-browser server-state] :as repl-env} {:keys [output-dir] :as opts}]
   (locking lock
     (when-not (:socket @server-state)
@@ -318,8 +335,8 @@
         (server/start repl-env)
         (let [base-url (str "http://" (:host repl-env) ":" (:port repl-env))]
           (if launch-browser
-            (browse/browse-url (str base-url "?rel=" (System/currentTimeMillis)))
-            (println "Waiting for browser to connect to" base-url "..."))))))
+            (maybe-browse-url base-url)
+            (println (waiting-to-connect-message base-url)))))))
   (swap! server-state update :listeners inc))
 
 (defrecord BrowserEnv []