smartplaylist: change encoding of additional field (#5563)

## Description

URL-encode additional item `fields` within generated EXTM3U playlists
instead of JSON-encoding them.
This is because JSON-encoding additional fields/attributes made it
difficult to parse the `EXTINF` line but using URL-encoding for these
values makes parsing easy (because URL-encoded values cannot contain
commas, quotation marks and spaces; see
[here](https://github.com/mgoltzsche/beets-webm3u/blob/v0.6.4/beetsplug/webm3u/playlist.py#L102)
and
[here](https://github.com/mgoltzsche/beets-webm3u/blob/v0.6.4/beetsplug/webm3u/playlist.py#L122)).

[I introduced the generation of additional EXTM3U item fields earlier
this year](#5121) and I want to
correct that now.

Author: JOJ0

beetsplug/smartplaylist.py

@@ -14,8 +14,8 @@
 
 """Generates smart playlists based on beets queries."""
 
-import json
 import os
+from urllib.parse import quote
 from urllib.request import pathname2url
 
 from beets import ui
@@ -327,7 +327,8 @@ def update_playlists(self, lib, pretend=False):
                         if extm3u:
                             attr = [(k, entry.item[k]) for k in keys]
                             al = [
-                                f" {a[0]}={json.dumps(str(a[1]))}" for a in attr
+                                f" {key}=\"{quote(str(value), safe='/:')}\""
+                                for key, value in attr
                             ]
                             attrs = "".join(al)
                             comment = "#EXTINF:{}{},{} - {}\n".format(

docs/changelog.rst

@@ -86,6 +86,8 @@ Other changes:
   wrong (outdated) commit. Now the tag is created in the same workflow step
   right after committing the version update.
   :bug:`5539`
+* :doc:`/plugins/smartplaylist`: URL-encode additional item `fields` within generated
+  EXTM3U playlists instead of JSON-encoding them.
 
 2.2.0 (December 02, 2024)
 -------------------------

docs/plugins/smartplaylist.rst

@@ -97,27 +97,25 @@ In case you want to export additional fields from the beets database into the
 generated playlists, you can do so by specifying them within the ``fields``
 configuration option and setting the ``output`` option to ``extm3u``.
 For instance the following configuration exports the ``id`` and ``genre``
-fields:
+fields::
 
     smartplaylist:
         playlist_dir: /data/playlists
         relative_to: /data/playlists
         output: extm3u
         fields:
-
             - id
             - genre
-
         playlists:
-
             - name: all.m3u
               query: ''
 
-A resulting ``all.m3u`` file could look as follows:
+Values of additional fields are URL-encoded.
+A resulting ``all.m3u`` file could look as follows::
 
     #EXTM3U
-    #EXTINF:805 id="1931" genre="Jazz",Miles Davis - Autumn Leaves
-    ../music/Albums/Miles Davis/Autumn Leaves/02 Autumn Leaves.mp3
+    #EXTINF:805 id="1931" genre="Progressive%20Rock",Led Zeppelin - Stairway to Heaven
+    ../music/singles/Led Zeppelin/Stairway to Heaven.mp3
 
 To give a usage example, the `webm3u`_ and `Beetstream`_ plugins read the
 exported ``id`` field, allowing you to serve your local m3u playlists via HTTP.

test/plugins/test_smartplaylist.py

@@ -283,7 +283,7 @@ def test_playlist_update_output_extm3u_fields(self):
         assert (
             content
             == b"#EXTM3U\n"
-            + b'#EXTINF:300 id="456" genre="Fake Genre",Fake Artist - fake Title\n'
+            + b'#EXTINF:300 id="456" genre="Fake%20Genre",Fake Artist - fake Title\n'
             + b"/tagada.mp3\n"
         )