Validate: Unique variable names

Related GraphQL-js commit: graphql/graphql-js@089caad

Author: syrusakbary

graphql/core/validation/rules/__init__.py

@@ -19,6 +19,7 @@
 from .unique_fragment_names import UniqueFragmentNames
 from .unique_input_field_names import UniqueInputFieldNames
 from .unique_operation_names import UniqueOperationNames
+from .unique_variable_names import UniqueVariableNames
 from .variables_are_input_types import VariablesAreInputTypes
 from .variables_in_allowed_position import VariablesInAllowedPosition
 
@@ -45,7 +46,8 @@
     DefaultValuesOfCorrectType,
     VariablesInAllowedPosition,
     OverlappingFieldsCanBeMerged,
-    UniqueInputFieldNames
+    UniqueInputFieldNames,
+    UniqueVariableNames
 ]
 
 __all__ = [
@@ -59,6 +61,7 @@
     'KnownTypeNames',
     'LoneAnonymousOperation',
     'NoFragmentCycles',
+    'UniqueVariableNames',
     'NoUndefinedVariables',
     'NoUnusedFragments',
     'NoUnusedVariables',

graphql/core/validation/rules/unique_variable_names.py

@@ -0,0 +1,27 @@
+from ...error import GraphQLError
+from .base import ValidationRule
+
+
+class UniqueVariableNames(ValidationRule):
+    __slots__ = 'known_variable_names',
+
+    def __init__(self, context):
+        super(UniqueVariableNames, self).__init__(context)
+        self.known_variable_names = {}
+
+    def enter_OperationDefinition(self, node, key, parent, path, ancestors):
+        self.known_variable_names = {}
+
+    def enter_VariableDefinition(self, node, key, parent, path, ancestors):
+        variable_name = node.variable.name.value
+        if variable_name in self.known_variable_names:
+            self.context.report_error(GraphQLError(
+                self.duplicate_variable_message(variable_name),
+                [self.known_variable_names[variable_name], node.variable.name]
+            ))
+        else:
+            self.known_variable_names[variable_name] = node.variable.name
+
+    @staticmethod
+    def duplicate_variable_message(operation_name):
+        return 'There can be only one variable named "{}".'.format(operation_name)

tests/core_validation/test_unique_variable_names.py

@@ -0,0 +1,30 @@
+from graphql.core.language.location import SourceLocation
+from graphql.core.validation.rules import UniqueVariableNames
+from .utils import expect_fails_rule, expect_passes_rule
+
+
+def duplicate_var(op_name, l1, c1, l2, c2):
+    return {
+        'message': UniqueVariableNames.duplicate_variable_message(op_name),
+        'locations': [SourceLocation(l1, c1), SourceLocation(l2, c2)]
+    }
+
+
+def test_unique_variable_names():
+    expect_passes_rule(UniqueVariableNames, '''
+      query A($x: Int, $y: String) { __typename }
+      query B($x: String, $y: Int) { __typename }
+    ''')
+
+
+def test_duplicate_variable_names():
+    expect_fails_rule(UniqueVariableNames, '''
+      query A($x: Int, $x: Int, $x: String) { __typename }
+      query B($x: String, $x: Int) { __typename }
+      query C($x: Int, $x: Int) { __typename }
+    ''', [
+        duplicate_var('x', 2, 16, 2, 25),
+        duplicate_var('x', 2, 16, 2, 34),
+        duplicate_var('x', 3, 16, 3, 28),
+        duplicate_var('x', 4, 16, 4, 25),
+    ])