@graphql-mesh/serve-runtime/esm/useChangingSchema.js

import { mapMaybePromise } from '@graphql-mesh/utils';
export function useChangingSchema(getSchema, schemaChanged) {
    let currentSchema;
    const schemaByRequest = new WeakMap();
    return {
        onPluginInit({ setSchema }) {
            schemaChanged(schema => {
                if (currentSchema !== schema) {
                    setSchema(schema);
                    currentSchema = schema;
                }
            });
        },
        onRequestParse({ request }) {
            return {
                onRequestParseDone() {
                    if (!currentSchema) {
                        // only if the schema is not already set do we want to get it
                        return mapMaybePromise(getSchema(), schema => {
                            schemaByRequest.set(request, schema);
                        }); // TODO: PromiseLike in Mesh MaybePromise is not assignable to type Yoga's PromiseOrValue
                    }
                },
            };
        },
        onEnveloped({ context, setSchema }) {
            const schema = context?.request && schemaByRequest.get(context.request);
            if (schema && currentSchema !== schema) {
                // the schema will be available in the request only if schemaChanged was never invoked
                // also avoid setting the schema multiple times by checking whether it was already set
                setSchema(schema);
                currentSchema = schema;
            }
        },
    };
}