Merge pull request #322 from whipper-team/feature/issue-279-disc-template-keyerror

Raise exception if template has invalid variables

README.md

@@ -250,7 +250,7 @@ read_offset = 6			; drive read offset in positive/negative frames (no leading +)
 unknown = True
 output_directory = ~/My Music
 track_template = new/%%A/%%y - %%d/%%t - %%n	; note: the format char '%' must be represented '%%'
-disc_template = %(track_template)s
+disc_template =  new/%%A/%%y - %%d/%%A - %%d
 # ...
 ```
 

whipper/common/program.py

@@ -196,6 +196,10 @@ class Program:
         """
         assert isinstance(outdir, unicode), "%r is not unicode" % outdir
         assert isinstance(template, unicode), "%r is not unicode" % template
+        matches = re.findall(r"%[^A,S,d,y,r,R,x,X]", template)
+        if '%' in template and matches:
+            raise ValueError('disc template string contains invalid '
+                             'variable(s): {}.'.format(', '.join(matches)))
         v = {}
         v['A'] = 'Unknown Artist'
         v['d'] = mbdiscid  # fallback for title