feat(graphql): extract subscription error policy

packages/javascript-api/src/lib/services/graphql/graphql-error.ts

@@ -0,0 +1,44 @@
+import { GraphQLErrorExtensions, SourceLocation } from 'graphql';
+
+/**
+ * A GraphQL error as returned by the Qminder API over a subscription or query.
+ */
+export interface QminderGraphQLError {
+  readonly message: string;
+  readonly errorType?: string | null;
+  readonly extensions?: GraphQLErrorExtensions | null;
+  readonly sourcePreview?: string | null;
+  readonly offendingToken?: string | null;
+  readonly locations?: SourceLocation[] | null;
+  readonly path?: (string | number)[] | null;
+}
+
+/**
+ * GraphQL subscription error types that the server will never resolve on retry.
+ * Subscriptions failing with one of these are surfaced to the caller immediately.
+ */
+const NON_RETRYABLE_SUBSCRIPTION_ERROR_TYPES = [
+  'BAD_REQUEST',
+  'FIELD_NOT_FOUND',
+  'INVALID_ARGUMENT',
+  'InvalidSyntax',
+  'NOT_FOUND',
+  'PERMISSION_DENIED',
+  'ValidationError',
+] as const;
+
+/**
+ * Whether any of the errors is a type the server will never resolve on retry,
+ * meaning the subscription should fail immediately rather than be retried.
+ */
+export function isNonRetryableSubscriptionError(
+  errors: QminderGraphQLError[],
+): boolean {
+  return errors
+    .filter((error) => error.errorType)
+    .some(({ errorType }) =>
+      (NON_RETRYABLE_SUBSCRIPTION_ERROR_TYPES as unknown as string[]).includes(
+        errorType,
+      ),
+    );
+}