Fixes matching to all when searching content in the fake client

Author: jajreidy

src/pubtools/pulplib/_impl/fake/match.py

@@ -123,6 +123,8 @@ def match_field_exists(_matcher, field, obj):
 @visit(InMatcher)
 def match_in(matcher, field, obj):
     value = get_field(field, obj)
+    if not matcher._values:
+        return True
     for elem in matcher._values:
         if elem == value:
             return True

tests/fake/test_fake_search_content.py

@@ -137,6 +137,15 @@ def test_search_content_by_type(populated_repo):
     ]
 
 
+def test_search_content_by_type_all(populated_repo):
+    """search_content for particular type returns matching content"""
+
+    crit = Criteria.with_field_in("content_type_id", [])
+    units = list(populated_repo.search_content(crit))
+    # assert we got all the units
+    assert len(units) == 7
+
+
 def test_search_content_with_fields(populated_repo):
     """search_content can limit fields"""