[Build] Fix WebUI js minifying error

Some users encoutered a bug where WebUI in browser show a white screen,
which indicates a problem with loading javascript files. The problem was
due to closure minifying failure leaving a zero-length deluge-all.js
file which broke the usual fallback mechanism to debug files.

* Fixed usage of ES6 const declaration breaking closure minifying.
* Cleanup minified files upon errors so no zero length files left
* Replaced broken and unmaintained slimit with rjsmin.
* Fixed unable to set dev or debug query args due to request args
requiring bytes.

DEPENDS.md

@@ -13,7 +13,7 @@ All modules will require the [common](#common) section dependencies.
 
 - [setuptools]
 - [intltool] - Optional: Desktop file translation for \*nix.
-- [closure-compiler] - Minify javascript (alternative is [slimit])
+- [closure-compiler] - Minify javascript (alternative is [rjsmin])
 
 ## Common
 
@@ -71,7 +71,7 @@ All modules will require the [common](#common) section dependencies.
 [setuptools]: https://setuptools.readthedocs.io/en/latest/
 [intltool]: https://freedesktop.org/wiki/Software/intltool/
 [closure-compiler]: https://developers.google.com/closure/compiler/
-[slimit]: https://slimit.readthedocs.io/en/latest/
+[rjsmin]: https://pypi.org/project/rjsmin/
 [openssl]: https://www.openssl.org/
 [pyopenssl]: https://pyopenssl.org
 [twisted]: https://twistedmatrix.com

deluge/ui/web/js/deluge-all/CopyMagnetWindow.js

@@ -51,7 +51,7 @@ Deluge.CopyMagnet = Ext.extend(Ext.Window, {
     },
     show: function (a) {
         Deluge.CopyMagnet.superclass.show.call(this);
-        const torrent = deluge.torrents.getSelected();
+        var torrent = deluge.torrents.getSelected();
         deluge.client.core.get_magnet_uri(torrent.id, {
             success: this.onRequestComplete,
             scope: this,

deluge/ui/web/server.py

@@ -592,13 +592,13 @@ class TopLevel(resource.Resource):
         uri_false = ('false', 'no', 'off', '0')
 
         debug_arg = None
-        req_dbg_arg = request.args.get('debug', [b''])[-1].decode().lower()
+        req_dbg_arg = request.args.get(b'debug', [b''])[-1].decode().lower()
         if req_dbg_arg in uri_true:
             debug_arg = True
         elif req_dbg_arg in uri_false:
             debug_arg = False
 
-        dev_arg = request.args.get('dev', [b''])[-1].decode().lower() in uri_true
+        dev_arg = request.args.get(b'dev', [b''])[-1].decode().lower() in uri_true
         dev_ver = 'dev' in common.get_version()
 
         script_type = 'normal'

minify_web_js.py

@@ -55,14 +55,14 @@ def minify_closure(file_in, file_out):
         return False
 
 
-# Closure outputs smallest files but it is a java-based command, so have slimit
+# Closure outputs smallest files but java-based command, can use rJSmin
 # as a python-only fallback.
 #
-#   deluge-all.js: Closure 127K, Slimit: 143K, JSMin: 162K
+#   deluge-all.js: Closure 131K, rJSmin: 148K
 #
 if not closure_cmd:
     try:
-        from slimit import minify as minify
+        from rjsmin import jsmin as minify
     except ImportError:
         print('Warning: No minifying command found.')
         minify = None
@@ -124,6 +124,8 @@ def minify_js_dir(source_dir):
     print('Minifying %s' % source_dir)
     if not minify_file(file_debug_js, file_minified_js):
         print('Warning: Failed minifying files %s, debug only' % source_dir)
+        if os.path.isfile(file_minified_js):
+            os.remove(file_minified_js)
 
 
 if __name__ == '__main__':

requirements-dev.txt

@@ -11,3 +11,4 @@ flake8-comprehensions
 flake8-debugger
 flake8-mock
 flake8-mutable
+rjsmin