planning

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

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+// @flow strict
+import { GraphQLError } from '../../error/GraphQLError';
+
+import type { ASTVisitor } from '../../language/visitor';
+
+import type { ValidationContext } from '../ValidationContext';
+
+/**
+ * Known fragment names
+ *
+ * A GraphQL document is only valid if all `...Fragment` fragment spreads refer
+ * to fragments defined in the same document.
+ */
+export function KnownFragmentNamesRule(context: ValidationContext): ASTVisitor {
+  return {
+    FragmentSpread(node) {
+      const fragmentName = node.name.value;
+      const fragment = context.getFragment(fragmentName);
+      if (!fragment) {
+        context.reportError(
+          new GraphQLError(`Unknown fragment "${fragmentName}".`, node.name),
+        );
+      }
+    },
+  };
+}