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node_modules/graphql/validation/rules/UniqueOperationNames.js.flow

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+// @flow strict
+
+import { GraphQLError } from '../../error/GraphQLError';
+import { type ASTVisitor } from '../../language/visitor';
+
+import { type ASTValidationContext } from '../ValidationContext';
+
+export function duplicateOperationNameMessage(operationName: string): string {
+  return `There can be only one operation named "${operationName}".`;
+}
+
+/**
+ * Unique operation names
+ *
+ * A GraphQL document is only valid if all defined operations have unique names.
+ */
+export function UniqueOperationNames(
+  context: ASTValidationContext,
+): ASTVisitor {
+  const knownOperationNames = Object.create(null);
+  return {
+    OperationDefinition(node) {
+      const operationName = node.name;
+      if (operationName) {
+        if (knownOperationNames[operationName.value]) {
+          context.reportError(
+            new GraphQLError(
+              duplicateOperationNameMessage(operationName.value),
+              [knownOperationNames[operationName.value], operationName],
+            ),
+          );
+        } else {
+          knownOperationNames[operationName.value] = operationName;
+        }
+      }
+      return false;
+    },
+    FragmentDefinition: () => false,
+  };
+}