player: add playlist-path properties

A bit of a long standing pain with scripting is that when opening a file
that gets interpreted as a playlist (like an m3u), the original path of
the file gets thrown away later. Workarounds basically consist of
getting the filename before mpv expands the path, but that's not really
reliable. Instead of throwing it away, save the original playlist path
by copying to the playlist entries when applicable (demuxer playlist and
the playlist option). Then expose these as properties: playlist-path for
the currently playing entry and playlist/N/playlist-path for each
specific entry. Closes #8508, #7605.

DOCS/interface-changes.rst

@@ -38,6 +38,7 @@ Interface changes
     - change type of `--sub-pos` to float
     - The remaining time printed in the terminal is now adjusted for speed by default.
       You can disable this with `--no-term-remaining-playtime`.
+    - add `playlist-path` and `playlist/N/playlist-path` properties
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

DOCS/man/input.rst

@@ -2776,6 +2776,11 @@ Property list
 ``playlist-count``
     Number of total playlist entries.
 
+``playlist-path``
+    The original path of the playlist for the current entry before mpv expanded
+    the entries. Unavailable if the file was not originally associated with a
+    playlist in some way.
+
 ``playlist``
     Playlist, current entry marked. Currently, the raw property value is
     useless.
@@ -2809,6 +2814,11 @@ Property list
         instance. Other commands, events, etc. use this as ``playlist_entry_id``
         fields.
 
+    ``playlist/N/playlist-path``
+        The original path of the playlist for this entry before mpv expanded
+        it. Unavailable if the file was not originally associated with a playlist
+        in some way.
+
     When querying the property with the client API using ``MPV_FORMAT_NODE``,
     or with Lua ``mp.get_property_native``, this will return a mpv_node with
     the following contents:

common/playlist.c

@@ -142,6 +142,14 @@ void playlist_add_file(struct playlist *pl, const char *filename)
     playlist_add(pl, playlist_entry_new(filename));
 }
 
+void playlist_populate_playlist_path(struct playlist *pl, const char *path)
+{
+    for (int n = 0; n < pl->num_entries; n++) {
+        struct playlist_entry *e = pl->entries[n];
+        e->playlist_path = talloc_strdup(e, path);
+    }
+}
+
 void playlist_shuffle(struct playlist *pl)
 {
     for (int n = 0; n < pl->num_entries; n++)

common/playlist.h

@@ -33,6 +33,7 @@ struct playlist_entry {
     uint64_t id;
 
     char *filename;
+    char *playlist_path;
 
     struct playlist_param *params;
     int num_params;
@@ -93,6 +94,7 @@ void playlist_move(struct playlist *pl, struct playlist_entry *entry,
                    struct playlist_entry *at);
 
 void playlist_add_file(struct playlist *pl, const char *filename);
+void playlist_populate_playlist_path(struct playlist *pl, const char *path);
 void playlist_shuffle(struct playlist *pl);
 void playlist_unshuffle(struct playlist *pl);
 struct playlist_entry *playlist_get_first(struct playlist *pl);

options/parse_commandline.c

@@ -194,13 +194,15 @@ int m_config_parse_mp_command_line(m_config_t *config, struct playlist *files,
                 // append the playlist to the local args
                 char *param0 = bstrdup0(NULL, p.param);
                 struct playlist *pl = playlist_parse_file(param0, NULL, global);
-                talloc_free(param0);
                 if (!pl) {
                     MP_FATAL(config, "Error reading playlist '%.*s'\n",
                              BSTR_P(p.param));
+                    talloc_free(param0);
                     goto err_out;
                 }
                 playlist_transfer_entries(files, pl);
+                playlist_populate_playlist_path(files, param0);
+                talloc_free(param0);
                 talloc_free(pl);
                 continue;
             }

player/command.c

@@ -3097,12 +3097,24 @@ static int get_playlist_entry(int item, int action, void *arg, void *ctx)
         {"playing",       SUB_PROP_BOOL(1), .unavailable = !playing},
         {"title",         SUB_PROP_STR(e->title), .unavailable = !e->title},
         {"id",            SUB_PROP_INT64(e->id)},
+        {"playlist-path", SUB_PROP_STR(e->playlist_path), .unavailable = !e->playlist_path},
         {0}
     };
 
     return m_property_read_sub(props, action, arg);
 }
 
+static int mp_property_playlist_path(void *ctx, struct m_property *prop,
+                                     int action, void *arg)
+{
+    MPContext *mpctx = ctx;
+    if (!mpctx->playlist->current)
+        return M_PROPERTY_UNAVAILABLE;
+
+    struct playlist_entry *e = mpctx->playlist->current;
+    return m_property_strdup_ro(action, arg, e->playlist_path);
+}
+
 static int mp_property_playlist(void *ctx, struct m_property *prop,
                                 int action, void *arg)
 {
@@ -3875,6 +3887,7 @@ static const struct m_property mp_properties_base[] = {
     {"edition-list", property_list_editions},
 
     {"playlist", mp_property_playlist},
+    {"playlist-path", mp_property_playlist_path},
     {"playlist-pos", mp_property_playlist_pos},
     {"playlist-pos-1", mp_property_playlist_pos_1},
     {"playlist-current-pos", mp_property_playlist_current_pos},

player/loadfile.c

@@ -1659,6 +1659,7 @@ static void play_current_file(struct MPContext *mpctx)
         if (watch_later)
             mp_delete_watch_later_conf(mpctx, mpctx->filename);
         struct playlist *pl = mpctx->demuxer->playlist;
+        playlist_populate_playlist_path(pl, mpctx->filename);
         transfer_playlist(mpctx, pl, &end_event.playlist_insert_id,
                           &end_event.playlist_insert_num_entries);
         mp_notify_property(mpctx, "playlist");