Refactored some regular expressions. Added changelog entry

Some more changes to the regular expressions in the "PATTERNS" list.
Also allow "_" as a separator, where only "-" was allowed.
Replaced similar regexps containing different combinations of \s, "-", "."
with a single regexp using a set of characters [\s.\-_].

beetsplug/fromfilename.py

@@ -28,26 +28,20 @@
 # Filename field extraction patterns.
 PATTERNS = [
     # Useful patterns.
-    r'^(?P<artist>.+)-(?P<title>.+)-(?P<tag>.*)$',
-    r'^(?P<track>\d+)\s*-(?P<artist>.+)-(?P<title>.+)-(?P<tag>.*)$',
-    r'^(?P<track>\d+)\s(?P<artist>.+)-(?P<title>.+)-(?P<tag>.*)$',
-    r'^(?P<artist>.+)-(?P<title>.+)$',
-    r'^(?P<track>\d+)\.\s*(?P<artist>.+)-(?P<title>.+)$',
-    r'^(?P<track>\d+)\s*-\s*(?P<artist>.+)-(?P<title>.+)$',
-    r'^(?P<track>\d+)\s*-(?P<artist>.+)-(?P<title>.+)$',
-    r'^(?P<track>\d+)\s(?P<artist>.+)-(?P<title>.+)$',
+    r'^(?P<artist>.+)[\-_](?P<title>.+)[\-_](?P<tag>.*)$',
+    r'^(?P<track>\d+)[\s.\-_]+(?P<artist>.+)[\-_](?P<title>.+)[\-_](?P<tag>.*)$',
+    r'^(?P<artist>.+)[\-_](?P<title>.+)$',
+    r'^(?P<track>\d+)[\s.\-_]+(?P<artist>.+)[\-_](?P<title>.+)$',
     r'^(?P<title>.+)$',
-    r'^(?P<track>\d+)\.\s*(?P<title>.+)$',
-    r'^(?P<track>\d+)\s*-\s*(?P<title>.+)$',
-    r'^(?P<track>\d+)\s(?P<title>.+)$',
+    r'^(?P<track>\d+)[\s.\-_]+(?P<title>.+)$',
+    r'^(?P<track>\d+)\s+(?P<title>.+)$',
     r'^(?P<title>.+) by (?P<artist>.+)$',
     r'^(?P<track>\d+).*$',
 ]
 
 # Titles considered "empty" and in need of replacement.
 BAD_TITLE_PATTERNS = [
     r'^$',
-    r'\d+?\s?-?\s*track\s*\d+',
 ]
 
 

docs/changelog.rst

@@ -80,6 +80,8 @@ Fixes:
   "Edit Candidates" option is used. :bug:`2734`
 * Fix a crash when numeric metadata fields contain just a minus or plus sign
   with no following numbers. Thanks to :user:`eigengrau`. :bug:`2741`
+* :doc:`/plugins/fromfilename`: Allow file names such as "01.mp3" to extract the track number.
+  Also allow "_" as a separator. Refactor some regular expressions. :bug:`2738`
 
 For developers: