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

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+// @flow strict
+
+import { GraphQLError } from '../../error/GraphQLError';
+import { type ASTVisitor } from '../../language/visitor';
+import { isEnumType } from '../../type/definition';
+
+import { type SDLValidationContext } from '../ValidationContext';
+
+export function duplicateEnumValueNameMessage(
+  typeName: string,
+  valueName: string,
+): string {
+  return `Enum value "${typeName}.${valueName}" can only be defined once.`;
+}
+
+export function existedEnumValueNameMessage(
+  typeName: string,
+  valueName: string,
+): string {
+  return `Enum value "${typeName}.${valueName}" already exists in the schema. It cannot also be defined in this type extension.`;
+}
+
+/**
+ * Unique enum value names
+ *
+ * A GraphQL enum type is only valid if all its values are uniquely named.
+ */
+export function UniqueEnumValueNames(
+  context: SDLValidationContext,
+): ASTVisitor {
+  const schema = context.getSchema();
+  const existingTypeMap = schema ? schema.getTypeMap() : Object.create(null);
+  const knownValueNames = Object.create(null);
+
+  return {
+    EnumTypeDefinition: checkValueUniqueness,
+    EnumTypeExtension: checkValueUniqueness,
+  };
+
+  function checkValueUniqueness(node) {
+    const typeName = node.name.value;
+
+    if (!knownValueNames[typeName]) {
+      knownValueNames[typeName] = Object.create(null);
+    }
+
+    if (node.values) {
+      const valueNames = knownValueNames[typeName];
+
+      for (const valueDef of node.values) {
+        const valueName = valueDef.name.value;
+
+        const existingType = existingTypeMap[typeName];
+        if (isEnumType(existingType) && existingType.getValue(valueName)) {
+          context.reportError(
+            new GraphQLError(
+              existedEnumValueNameMessage(typeName, valueName),
+              valueDef.name,
+            ),
+          );
+        } else if (valueNames[valueName]) {
+          context.reportError(
+            new GraphQLError(
+              duplicateEnumValueNameMessage(typeName, valueName),
+              [valueNames[valueName], valueDef.name],
+            ),
+          );
+        } else {
+          valueNames[valueName] = valueDef.name;
+        }
+      }
+    }
+
+    return false;
+  }
+}