flow like the river

BACK_BACK/node_modules/graphql/subscription/subscribe.d.ts

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+import { Maybe } from '../jsutils/Maybe';
+
+import { DocumentNode } from '../language/ast';
+import { ExecutionResult } from '../execution/execute';
+import { GraphQLSchema } from '../type/schema';
+import { GraphQLFieldResolver } from '../type/definition';
+
+export interface SubscriptionArgs {
+  schema: GraphQLSchema;
+  document: DocumentNode;
+  rootValue?: any;
+  contextValue?: any;
+  variableValues?: Maybe<Record<string, any>>;
+  operationName?: Maybe<string>;
+  fieldResolver?: Maybe<GraphQLFieldResolver<any, any>>;
+  subscribeFieldResolver?: Maybe<GraphQLFieldResolver<any, any>>;
+}
+
+/**
+ * Implements the "Subscribe" algorithm described in the GraphQL specification.
+ *
+ * Returns a Promise which resolves to either an AsyncIterator (if successful)
+ * or an ExecutionResult (client error). The promise will be rejected if a
+ * server error occurs.
+ *
+ * If the client-provided arguments to this function do not result in a
+ * compliant subscription, a GraphQL Response (ExecutionResult) with
+ * descriptive errors and no data will be returned.
+ *
+ * If the the source stream could not be created due to faulty subscription
+ * resolver logic or underlying systems, the promise will resolve to a single
+ * ExecutionResult containing `errors` and no `data`.
+ *
+ * If the operation succeeded, the promise resolves to an AsyncIterator, which
+ * yields a stream of ExecutionResults representing the response stream.
+ *
+ * Accepts either an object with named arguments, or individual arguments.
+ */
+export function subscribe(
+  args: SubscriptionArgs,
+): Promise<AsyncIterableIterator<ExecutionResult> | ExecutionResult>;
+
+export function subscribe(
+  schema: GraphQLSchema,
+  document: DocumentNode,
+  rootValue?: any,
+  contextValue?: any,
+  variableValues?: Maybe<{ [key: string]: any }>,
+  operationName?: Maybe<string>,
+  fieldResolver?: Maybe<GraphQLFieldResolver<any, any>>,
+  subscribeFieldResolver?: Maybe<GraphQLFieldResolver<any, any>>,
+): Promise<AsyncIterableIterator<ExecutionResult> | ExecutionResult>;
+
+/**
+ * Implements the "CreateSourceEventStream" algorithm described in the
+ * GraphQL specification, resolving the subscription source event stream.
+ *
+ * Returns a Promise<AsyncIterable>.
+ *
+ * If the client-provided invalid arguments, the source stream could not be
+ * created, or the resolver did not return an AsyncIterable, this function will
+ * will throw an error, which should be caught and handled by the caller.
+ *
+ * A Source Event Stream represents a sequence of events, each of which triggers
+ * a GraphQL execution for that event.
+ *
+ * This may be useful when hosting the stateful subscription service in a
+ * different process or machine than the stateless GraphQL execution engine,
+ * or otherwise separating these two steps. For more on this, see the
+ * "Supporting Subscriptions at Scale" information in the GraphQL specification.
+ */
+export function createSourceEventStream(
+  schema: GraphQLSchema,
+  document: DocumentNode,
+  rootValue?: any,
+  contextValue?: any,
+  variableValues?: { [key: string]: any },
+  operationName?: Maybe<string>,
+  fieldResolver?: Maybe<GraphQLFieldResolver<any, any>>,
+): Promise<AsyncIterable<any> | ExecutionResult>;