play: Insert arguments anywhere (#1532)

beetsplug/play.py

@@ -25,6 +25,10 @@ from beets import util
 from os.path import relpath
 from tempfile import NamedTemporaryFile
 
+# Indicate where arguments should be inserted into the command string.
+# If this is missing, they're placed at the end.
+ARGS_MARKER = '$args'
+
 
 class PlayPlugin(BeetsPlugin):
 
@@ -63,6 +67,9 @@ class PlayPlugin(BeetsPlugin):
 
         # Add optional arguments to the player command.
         if opts.args:
+            if ARGS_MARKER in command_str:
+                command_str = command_str.replace(ARGS_MARKER, opts.args)
+            else:
                 command_str = "{} {}".format(command_str, opts.args)
 
         # Perform search by album and add folders rather than tracks to

docs/plugins/play.rst

@@ -66,3 +66,13 @@ to get beets to execute this command::
     mplayer -quiet -shuffle /path/to/playlist.m3u
 
 instead of the default.
+
+If you need to insert arguments somewhere other than the end of the
+``command`` string, use ``$args`` to indicate where to insert them. For
+example::
+
+    play:
+        command: mpv $args --playlist
+
+indicates that you need to insert extra arguments before specifying the
+playlist.