Fix bugs with saving tags in yaml.

- now saves tag set as list (maybe the save_meta function should be
  moved to paper.py)
- updates test to actually test storing of metadata

papers/files.py

@@ -108,7 +108,10 @@ def save_bibdata(bib_data, filepath):
 
 
 def save_meta(meta_data, filepath):
-    write_yamlfile(filepath, meta_data)
+    new_meta = meta_data.copy()
+    # Cannot store sets in yaml
+    new_meta['tags'] = list(new_meta['tags'])
+    write_yamlfile(filepath, new_meta)
 
 
 # is this function ever used? 08/06/2013

papers/paper.py

@@ -20,7 +20,7 @@ CITEKEY_EXCLUDE_RE = re.compile('[%s]'
 
 BASE_META = {
     'external-document': None,
-    'tags': [],
+    'tags': set(),
     'notes': [],
     }
 

tests/fixtures.py

@@ -8,6 +8,7 @@ turing1950.bibentry.fields['title'] = u'Computing machinery and intelligence.'
 turing1950.bibentry.fields['year'] = u'1950'
 turing1950.bibentry.persons['author'] = [Person(u'Alan Turing')]
 turing1950.citekey = turing1950.generate_citekey()
+turing1950.tags = ['computer', 'AI']
 
 
 doe2013 = Paper()

tests/test_paper.py

@@ -24,7 +24,7 @@ entries:
 META = """
 external-document: null
 notes: []
-tags: []
+tags: ['AI', 'computer']
 """