remove hawk library used for file watching

Only used to be used on macOS since it was slightly faster
than the default JVM implementation. However in Big Sur it seems
to cause issues and break completely or just be a lot slower.

Win/Linux are unaffected since they always used the default JVM
implemenation. Big Sur seems to be faster. Previous macOS version
might get a tad slower but I haven't tested that in a long time
and it used to be no more than 2secs which is fine. Better than
relying on an unmaintained possibly broken library.

fixes #837
fixes #774

project.clj

@@ -76,8 +76,6 @@
    ;; for pathom
    [org.clojure/test.check "1.1.0"]
 
-   ;; experimental
-   [hawk "0.2.11"]
    [thheller/shadow-cljsjs "0.0.21"]]
 
   :source-paths

src/main/shadow/cljs/devtools/server/fs_watch.clj

@@ -1,31 +1,84 @@
 (ns shadow.cljs.devtools.server.fs-watch
-  (:require [shadow.jvm-log :as log]
-            [clojure.string :as str]))
+  (:require [shadow.build.api :as cljs]
+            [clojure.core.async :as async :refer (alt!! thread >!!)]
+            [shadow.cljs.devtools.server.util :as util]
+            [shadow.cljs.devtools.server.system-bus :as system-bus]
+            [clojure.java.io :as io]
+            [clojure.string :as str]
+            [shadow.build.resource :as rc])
+  (:import (shadow.util FileWatcher)
+           (java.io File)))
 
+(defn service? [x]
+  (and (map? x)
+       (::service x)))
 
-;; hawk already uses the jvm watcher on win/linux
-;; not much benefit doing this again
+(defn poll-changes [{:keys [dir ^FileWatcher watcher]}]
+  (let [changes (.pollForChanges watcher)]
+    (when (seq changes)
+      (->> changes
+           (map (fn [[name event]]
+                  {:dir dir
+                   :name (rc/normalize-name name)
+                   :ext (when-let [x (str/last-index-of name ".")]
+                          (subs name (inc x)))
+                   :file (io/file dir name)
+                   :event event}))
+           ;; ignore empty files
+           (remove (fn [{:keys [event ^File file] :as x}]
+                     (and (not= event :del)
+                          (zero? (.length file)))))
+           ))))
 
-(def os-name (System/getProperty "os.name"))
+(defn watch-loop
+  [watch-dirs control publish-fn]
+
+  (loop []
+    (alt!!
+      control
+      ([_]
+        :terminated)
+
+      (async/timeout 500)
+      ([_]
+        (let [fs-updates
+              (->> watch-dirs
+                   (mapcat poll-changes)
+                   (into []))]
+
+          (when (seq fs-updates)
+            (publish-fn fs-updates))
+
+          (recur)))))
+
+  ;; shut down watchers when loop ends
+  (doseq [{:keys [^FileWatcher watcher]} watch-dirs]
+    (.close watcher))
+
+  ::shutdown-complete)
 
 (defn start [config directories file-exts publish-fn]
-  (let [ns-sym
-        (if (and (str/includes? os-name "Mac") (not (false? (:hawk config))))
-          ;; macOS doesn't have native support so it uses polling
-          ;; which means 2sec delay, hawk does the native stuff
-          ;; so its a lot faster but doesn't properly support delete
-          'shadow.cljs.devtools.server.fs-watch-hawk
-          ;; jvm on windows/linux supports watch fine
-          'shadow.cljs.devtools.server.fs-watch-jvm)]
-
-    (log/debug ::fs-watch {:ns ns-sym})
-
-    (require ns-sym)
-
-    (let [start-var (ns-resolve ns-sym 'start)]
-      (-> (start-var config directories file-exts publish-fn)
-          (assoc ::ns ns-sym)))))
-
-(defn stop [{::keys [ns] :as svc}]
-  (let [stop-var (ns-resolve ns 'stop)]
-    (stop-var svc)))
+  {:pre [(every? #(instance? File %) directories)
+         (coll? file-exts)
+         (every? string? file-exts)]}
+  (let [control
+        (async/chan)
+
+        watch-dirs
+        (->> directories
+             (map (fn [^File dir]
+                    {:dir dir
+                     :watcher (FileWatcher/create dir (vec file-exts))}))
+             (into []))]
+
+    {::service true
+     :control control
+     :watch-dirs watch-dirs
+     :thread (thread (watch-loop watch-dirs control publish-fn))}))
+
+(defn stop [{:keys [control thread] :as svc}]
+  {:pre [(service? svc)]}
+  (async/close! control)
+  (async/<!! thread))
+
+

src/repl/shadow/cljs/watch_test.clj

@@ -2,8 +2,7 @@
   (:require
     [clojure.test :refer (is deftest)]
     [clojure.java.io :as io]
-    [shadow.cljs.devtools.server.fs-watch-jvm :as fs-jvm]
-    [shadow.cljs.devtools.server.fs-watch-hawk :as fs-hawk]))
+    [shadow.cljs.devtools.server.fs-watch :as fs]))
 
 
 (comment