rss: Replace crashy double-formatting with standard format_token_replace (#370)

* rss: Simplify entry formatting

* Use format_token_replace

* Apply suggestions

* add `rss-format` config migration

---------

Co-authored-by: David Schultz <me@zpld.me>

modules/rss.py

@@ -1,7 +1,7 @@
 #--depends-on config
 #--depends-on shorturl
 
-import difflib, hashlib, time
+import difflib, hashlib, time, re
 from src import ModuleManager, utils
 import feedparser
 
@@ -13,22 +13,39 @@ SETTING_BIND = utils.Setting("rss-bindhost",
     "Interval (in seconds) between RSS polls", example="120"))
 @utils.export("channelset", utils.BoolSetting("rss-shorten",
     "Whether or not to shorten RSS urls"))
-@utils.export("channelset", utils.Setting("rss-format", "Format of RSS announcements", example="$longtitle: $title - $link [$author]"))
+@utils.export("channelset", utils.Setting("rss-format", "Format of RSS announcements", example="${longtitle}: ${title} - ${link} [${author}]"))
 @utils.export("serverset", SETTING_BIND)
 @utils.export("channelset", SETTING_BIND)
 class Module(ModuleManager.BaseModule):
     _name = "RSS"
+    def _migrate_formats(self):
+        count = 0
+        migration_sub = re.compile(r"(?:\$|{)+(?P<variable>[^}\s]+)(?:})?")
+        old_formats = self.bot.database.execute_fetchall("""
+            SELECT channel_id, value FROM channel_settings
+            WHERE setting = 'rss-format'
+        """)
+
+        for channel_id, format in old_formats:
+            new_format = migration_re.sub(r"${\1}", format)
+            self.bot.database.execute("""
+                UPDATE channel_settings SET value = ?
+                WHERE setting = 'rss-format'
+                AND channel_id = ?
+            """, [new_format, channel_id])
+            count += 1
+
+        self.log.info("Successfully migrated %d rss-format settings" % count)
+
     def on_load(self):
+        if self.bot.get_setting("rss-fmt-migration", False):
+            self.log.info("Attempting to migrate old rss-format settings")
+            self._migrate_formats()
+            self.bot.set_setting("rss-fmt-migration", True)
         self.timers.add("rss-feeds", self._timer,
             self.bot.get_setting("rss-interval", RSS_INTERVAL))
 
     def _format_entry(self, server, channel, feed_title, entry, shorten):
-        title = utils.parse.line_normalise(utils.http.strip_html(
-            entry["title"]))
-
-        author = entry.get("author", "unknown author")
-        author = "%s" % author if author else ""
-
         link = entry.get("link", None)
         if shorten:
             try:
@@ -37,16 +54,21 @@ class Module(ModuleManager.BaseModule):
                 pass
         link = "%s" % link if link else ""
 
-        feed_title_str = "%s" % feed_title if feed_title else ""
+        variables = dict(
+            longtitle=feed_title or "",
+            title=utils.parse.line_normalise(utils.http.strip_html(
+                entry["title"])),
+            link=link or "",
+            author=entry.get("author", "unknown author") or "",
+        )
+        variables.update(entry)
+
         # just in case the format starts keyerroring and you're not sure why
         self.log.trace("RSS Entry: " + str(entry))
-        try:
+        template = channel.get_setting("rss-format", "${longtitle}: ${title} by ${author} - ${link}")
-            format = channel.get_setting("rss-format", "$longtitle: $title by $author - $link").replace("$longtitle", feed_title_str).replace("$title", title).replace("$link", link).replace("$author", author).format(**entry)
+        _, formatted = utils.parse.format_token_replace(template, variables)
-        except KeyError:
+        return formatted
-            self.log.warn(f"Failed to format RSS entry for {channel}. Falling back to default format.")
-            format = f"{feed_title_str}: {title} by {author} - {link}"
 
-        return format
 
     def _timer(self, timer):
         start_time = time.monotonic()