fix: allow empty-string content (#49)

ethpm_types/source.py

@@ -102,7 +102,7 @@ def fetch_content(self) -> str:
         """
 
         # NOTE: This is a trapdoor to bypass fetching logic if already available
-        if self.content:
+        if self.content is not None:
             return self.content
 
         if len(self.urls) == 0:
@@ -160,7 +160,7 @@ def content_is_valid(self) -> bool:
         """
 
         # NOTE: Per EIP-2678, checksum is not needed if content does not need to be fetched
-        if self.content:
+        if self.content is not None:
             return True
 
         # NOTE: Per EIP-2678, Checksum is not required if a URL is content addressed.

tests/test_corrupt_source.py

@@ -20,6 +20,16 @@ def bad_checksum() -> Source:
     )
 
 
+@pytest.fixture
+def empty_source() -> Source:
+    return Source.parse_obj({"content": ""})
+
+
 def test_corrupt_source(bad_checksum, no_checksum):
     assert not no_checksum.content_is_valid()
     assert not bad_checksum.content_is_valid()
+
+
+def test_empty_source(empty_source):
+    assert empty_source.fetch_content() == ""
+    assert empty_source.content_is_valid()