Return None instead of empty strings

Signed-off-by: Ayan Sinha Mahapatra <ayansmahapatra@gmail.com>

Author: AyanSinhaMahapatra

src/summarycode/score.py

@@ -452,7 +452,7 @@ def get_primary_license(declared_license_expressions):
         if len(single_expressions) == 1:
             return single_expressions[0]
         else:
-            return ''
+            return None
 
     # Group single expressions to joined expressions to see if single
     # expressions are accounted for in a joined expression
@@ -474,4 +474,4 @@ def get_primary_license(declared_license_expressions):
     if len(single_expressions_by_joined_expressions) == 1 and not not_in_joined_expressions:
         return next(iter(single_expressions_by_joined_expressions))
     else:
-        return ''
+        return None

src/summarycode/summarizer.py

@@ -204,10 +204,10 @@ def get_primary_language(programming_language_tallies):
     programming_languages_by_count = {
         entry['count']: entry['value'] for entry in programming_language_tallies
     }
-    primary_language = ''
+    primary_language = None
     if programming_languages_by_count:
         highest_count = max(programming_languages_by_count)
-        primary_language = programming_languages_by_count[highest_count] or ''
+        primary_language = programming_languages_by_count[highest_count] or None
     return primary_language
 
 
@@ -219,7 +219,7 @@ def get_origin_info_from_top_level_packages(top_level_packages, codebase):
     ``codebase``.
     """
     if not top_level_packages:
-        return '', [], ''
+        return None, [], None
 
     license_expressions = []
     programming_languages = []
@@ -250,7 +250,7 @@ def get_origin_info_from_top_level_packages(top_level_packages, codebase):
         relation='AND',
     )
 
-    declared_license_expression = ''
+    declared_license_expression = None
     if combined_declared_license_expression:
         declared_license_expression = str(
             Licensing().parse(combined_declared_license_expression).simplify()
@@ -283,7 +283,7 @@ def get_origin_info_from_top_level_packages(top_level_packages, codebase):
 
     # Programming language
     unique_programming_languages = unique(programming_languages)
-    primary_language = ''
+    primary_language = None
     if len(unique_programming_languages) == 1:
         primary_language = unique_programming_languages[0]