🐛 modstool: Fix handling multiple <mods:language>

There may be multiple <mods:language> tags with mods:languageTerm children,
that should be merged into one language_languageTerm column

qurator/modstool/modstool.py

@@ -320,8 +320,8 @@ def mods_to_dict(mods, raise_errors=True):
                 value['language_{}'.format(sub_tag)] = s
         elif tag == '{http://www.loc.gov/mods/v3}languageTerm':
             value['languageTerm'] = TagGroup(tag, group) \
-                .is_singleton().has_attributes({'authority': 'iso639-2b', 'type': 'code'}) \
-                .text()
+                .has_attributes({'authority': 'iso639-2b', 'type': 'code'}) \
+                .text_set()
         elif tag == '{http://www.loc.gov/mods/v3}scriptTerm':
             value['scriptTerm'] = TagGroup(tag, group) \
                 .fix_script_term() \

qurator/modstool/tests/test_modstool.py

@@ -9,9 +9,20 @@ def dict_fromstring(x):
     """Helper function to parse a MODS XML string to a flattened dict"""
     return flatten(mods_to_dict(ET.fromstring(x)))
 
-def test_languageTerm():
+def test_single_language_languageTerm():
+    d = dict_fromstring("""
+    <mods:mods xmlns:mods="http://www.loc.gov/mods/v3">
+        <mods:language>
+            <mods:languageTerm authority="iso639-2b" type="code">lat</mods:languageTerm>
+            <mods:languageTerm authority="iso639-2b" type="code">ger</mods:languageTerm>
+        </mods:language>
+    </mods:mods>
+    """)
+    assert d['language_languageTerm'] == {'ger', 'lat'}
+
+def test_multitple_language_languageTerm():
     """
-    Different languages have multiple mods:language elements.
+    Different languages MAY have multiple mods:language elements.
     See MODS-AP 2.3.1
     """
     d = dict_fromstring("""