Extract type comparators into the public API

Related GraphQL-js commit: graphql/graphql-js@aff18e6

Author: syrusakbary

graphql/core/utils/type_comparators.py

@@ -1,4 +1,5 @@
 from ..type.definition import (GraphQLList, GraphQLNonNull, GraphQLObjectType,
+                               GraphQLInterfaceType, GraphQLUnionType,
                                is_abstract_type)
 
 
@@ -38,3 +39,18 @@ def is_type_sub_type_of(maybe_subtype, super_type):
         return True
 
     return False
+
+
+def do_types_overlap(t1, t2):
+    if t1 == t2:
+        return True
+    if isinstance(t1, GraphQLObjectType):
+        if isinstance(t2, GraphQLObjectType):
+            return False
+        return t1 in t2.get_possible_types()
+    if isinstance(t1, GraphQLInterfaceType) or isinstance(t1, GraphQLUnionType):
+        if isinstance(t2, GraphQLObjectType):
+            return t2 in t1.get_possible_types()
+
+        t1_type_names = {possible_type.name: possible_type for possible_type in t1.get_possible_types()}
+        return any(t.name in t1_type_names for t in t2.get_possible_types())

graphql/core/validation/rules/possible_fragment_spreads.py

@@ -1,7 +1,6 @@
 from ...error import GraphQLError
-from ...type.definition import (GraphQLInterfaceType, GraphQLObjectType,
-                                GraphQLUnionType)
 from ...utils.type_from_ast import type_from_ast
+from ...utils.type_comparators import do_types_overlap
 from .base import ValidationRule
 
 
@@ -10,7 +9,7 @@ class PossibleFragmentSpreads(ValidationRule):
     def enter_InlineFragment(self, node, key, parent, path, ancestors):
         frag_type = self.context.get_type()
         parent_type = self.context.get_parent_type()
-        if frag_type and parent_type and not self.do_types_overlap(frag_type, parent_type):
+        if frag_type and parent_type and not do_types_overlap(frag_type, parent_type):
             self.context.report_error(GraphQLError(
                 self.type_incompatible_anon_spread_message(parent_type, frag_type),
                 [node]
@@ -20,7 +19,7 @@ def enter_FragmentSpread(self, node, key, parent, path, ancestors):
         frag_name = node.name.value
         frag_type = self.get_fragment_type(self.context, frag_name)
         parent_type = self.context.get_parent_type()
-        if frag_type and parent_type and not self.do_types_overlap(frag_type, parent_type):
+        if frag_type and parent_type and not do_types_overlap(frag_type, parent_type):
             self.context.report_error(GraphQLError(
                 self.type_incompatible_spread_message(frag_name, parent_type, frag_type),
                 [node]
@@ -31,21 +30,6 @@ def get_fragment_type(context, name):
         frag = context.get_fragment(name)
         return frag and type_from_ast(context.get_schema(), frag.type_condition)
 
-    @staticmethod
-    def do_types_overlap(t1, t2):
-        if t1 == t2:
-            return True
-        if isinstance(t1, GraphQLObjectType):
-            if isinstance(t2, GraphQLObjectType):
-                return False
-            return t1 in t2.get_possible_types()
-        if isinstance(t1, GraphQLInterfaceType) or isinstance(t1, GraphQLUnionType):
-            if isinstance(t2, GraphQLObjectType):
-                return t2 in t1.get_possible_types()
-
-            t1_type_names = {possible_type.name: possible_type for possible_type in t1.get_possible_types()}
-            return any(t.name in t1_type_names for t in t2.get_possible_types())
-
     @staticmethod
     def type_incompatible_spread_message(frag_name, parent_type, frag_type):
         return 'Fragment {} cannot be spread here as objects of type {} can never be of type {}'.format(frag_name,