flow like the river

BACK_BACK/node_modules/graphql/validation/rules/ExecutableDefinitionsRule.js.flow

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+// @flow strict
+import { GraphQLError } from '../../error/GraphQLError';
+
+import type { ASTVisitor } from '../../language/visitor';
+import { Kind } from '../../language/kinds';
+import { isExecutableDefinitionNode } from '../../language/predicates';
+
+import type { ASTValidationContext } from '../ValidationContext';
+
+/**
+ * Executable definitions
+ *
+ * A GraphQL document is only valid for execution if all definitions are either
+ * operation or fragment definitions.
+ */
+export function ExecutableDefinitionsRule(
+  context: ASTValidationContext,
+): ASTVisitor {
+  return {
+    Document(node) {
+      for (const definition of node.definitions) {
+        if (!isExecutableDefinitionNode(definition)) {
+          const defName =
+            definition.kind === Kind.SCHEMA_DEFINITION ||
+            definition.kind === Kind.SCHEMA_EXTENSION
+              ? 'schema'
+              : '"' + definition.name.value + '"';
+          context.reportError(
+            new GraphQLError(
+              `The ${defName} definition is not executable.`,
+              definition,
+            ),
+          );
+        }
+      }
+      return false;
+    },
+  };
+}