GraphQLError: fix empty locations if error got nodes without locations

Replicates graphql/graphql-js@b936411

Author: Cito

src/graphql/error/graphql_error.py

@@ -137,31 +137,26 @@ def __init__(
         if nodes and not isinstance(nodes, list):
             nodes = [nodes]  # type: ignore
         self.nodes = nodes or None  # type: ignore
+        node_locations = (
+            [node.loc for node in nodes if node.loc] if nodes else []  # type: ignore
+        )
 
         # Compute locations in the source for the given nodes/positions.
         self.source = source
-        if not source and nodes:
-            node = nodes[0]  # type: ignore
-            if node and node.loc and node.loc.source:
-                self.source = node.loc.source
-
-        if not positions and nodes:
-            positions = [node.loc.start for node in nodes if node.loc]  # type: ignore
+        if not source and node_locations:
+            loc = node_locations[0]
+            if loc.source:  # pragma: no cover else
+                self.source = loc.source
+        if not positions and node_locations:
+            positions = [loc.start for loc in node_locations]
         self.positions = positions or None
-
         if positions and source:
             locations: Optional[List["SourceLocation"]] = [
                 source.get_location(pos) for pos in positions
             ]
-        elif nodes:
-            locations = [
-                node.loc.source.get_location(node.loc.start)
-                for node in nodes  # type: ignore
-                if node.loc
-            ]
         else:
-            locations = None
-        self.locations = locations
+            locations = [loc.source.get_location(loc.start) for loc in node_locations]
+        self.locations = locations or None
 
         if original_error:
             self.__traceback__ = original_error.__traceback__

tests/error/test_graphql_error.py

@@ -116,6 +116,15 @@ def converts_node_with_loc_start_zero_to_positions_and_locations():
         assert e.positions == [0]
         assert e.locations == [(1, 1)]
 
+    def converts_node_without_location_to_source_positions_and_locations_as_none():
+        document_node = parse("{ foo }", no_location=True)
+
+        e = GraphQLError("msg", document_node)
+        assert e.nodes == [document_node]
+        assert e.source is None
+        assert e.positions is None
+        assert e.locations is None
+
     def converts_source_and_positions_to_locations():
         e = GraphQLError("msg", None, source, [6])
         assert e.nodes is None

tests/validation/test_validation.py

@@ -158,7 +158,6 @@ def _validate_document(max_errors=None):
     def _invalid_field_error(field_name: str):
         return {
             "message": f"Cannot query field '{field_name}' on type 'QueryRoot'.",
-            "locations": [],
         }
 
     def when_max_errors_is_equal_to_number_of_errors():