fix(pagination): Handle empty next_page_token

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

src/frequenz/client/common/pagination/__init__.py

@@ -124,9 +124,15 @@ def from_proto(
         Returns:
             Info object corresponding to the protobuf message.
         """
+        # We check for truthiness here to handle both cases where the token is
+        # not set (defaults to "") or is explicitly set to "". In both
+        # situations, we want to return `None`. Using `HasField("next_page_token")`
+        # would not handle the case where the token is explicitly set to "".
         return cls(
             total_items=pagination_info.total_items,
-            next_page_token=pagination_info.next_page_token,
+            next_page_token=pagination_info.next_page_token
+            if pagination_info.next_page_token
+            else None,
         )
 
     def to_proto_v1alpha8(self) -> PBPaginationInfoAlpha8:

tests/test_pagination.py

@@ -30,6 +30,38 @@ def test_pagination_info_from_proto_v1alpha8() -> None:
     assert info.next_page_token == "token"
 
 
+def test_pagination_info_from_proto_v1_no_token() -> None:
+    """Test the PaginationInfo from_proto method with v1 proto and no token."""
+    proto = PBPaginationInfo(total_items=100)
+    info = PaginationInfo.from_proto(proto)
+    assert info.total_items == 100
+    assert info.next_page_token is None
+
+
+def test_pagination_info_from_proto_v1alpha8_no_token() -> None:
+    """Test the PaginationInfo from_proto method with v1alpha8 proto and no token."""
+    proto = PBPaginationInfoAlpha8(total_items=100)
+    info = PaginationInfo.from_proto(proto)
+    assert info.total_items == 100
+    assert info.next_page_token is None
+
+
+def test_pagination_info_from_proto_v1_empty_token() -> None:
+    """Test the PaginationInfo from_proto method with v1 proto and an empty token."""
+    proto = PBPaginationInfo(total_items=100, next_page_token="")
+    info = PaginationInfo.from_proto(proto)
+    assert info.total_items == 100
+    assert info.next_page_token is None
+
+
+def test_pagination_info_from_proto_v1alpha8_empty_token() -> None:
+    """Test the PaginationInfo from_proto method with v1alpha8 proto and an empty token."""
+    proto = PBPaginationInfoAlpha8(total_items=100, next_page_token="")
+    info = PaginationInfo.from_proto(proto)
+    assert info.total_items == 100
+    assert info.next_page_token is None
+
+
 def test_pagination_info_to_proto_v1() -> None:
     """Test the PaginationInfo to_proto method."""
     info = PaginationInfo(total_items=100, next_page_token="token")