Simple merging algorithm for multiple GraphQL schema files into AppSync

loadSchemas.js

"use strict";
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    if (k2 === undefined) k2 = k;
    Object.defineProperty(o, k2, { enumerable: true, get: function() { return m[k]; } });
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var __importStar = (this && this.__importStar) || function (mod) {
    if (mod && mod.__esModule) return mod;
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    if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
    __setModuleDefault(result, mod);
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Object.defineProperty(exports, "__esModule", { value: true });
exports.loadSchemas = void 0;
const appSync = __importStar(require("@aws-cdk/aws-appsync"));
const graphql_1 = require("graphql");
const path_1 = require("path");
const fs_1 = require("fs");
const loop = (documents, schema) => {
    if (documents.length <= 0) {
        return schema;
    }
    const types = schema.getTypeMap();
    // This iteration, only include documents that either only add new types or extend existing types.
    const documentsToInclude = documents.filter((d) => d.definitions.find((def) => (def.kind === 'EnumTypeExtension' ||
        def.kind === 'InputObjectTypeExtension' ||
        def.kind === 'InterfaceTypeExtension' ||
        def.kind === 'ObjectTypeExtension' ||
        def.kind === 'ScalarTypeExtension' ||
        def.kind === 'UnionTypeExtension') &&
        !(def.name.value in types)) == null);
    if (documentsToInclude.length === 0) {
        const dependencies = JSON.stringify(documents.map((d) => { var _a; return (_a = d.loc) === null || _a === void 0 ? void 0 : _a.source.name; }));
        throw new Error(`Unable to load schemas, possible circular dependency found: ${dependencies}`);
    }
    const remainingDocuments = documents.filter((v) => !documentsToInclude.includes(v));
    return loop(remainingDocuments, documentsToInclude.reduce((acc, v) => (0, graphql_1.extendSchema)(acc, v), schema));
};

/**
 * Loads a set of graphql schema files into an AppSync schema.
 *
 * The order of graphql input schemas doesn't matter, this will load them in an order that just works.
 *
 * @param pluginDirs A list of folders with schema files in them.
 * @returns
 */
const loadSchemas = (pluginDirs) => {
    const partialSchemas = pluginDirs.map((f) => (0, graphql_1.parse)(new graphql_1.Source((0, fs_1.readFileSync)((0, path_1.join)(f, 'schema.graphql')).toString('utf-8'), (0, path_1.join)(f, 'schema.graphql'))));
    const gqlSchema = loop(partialSchemas, new graphql_1.GraphQLSchema({}));
    const schema = new appSync.Schema();
    schema.addToSchema('schema { query: Query }');
    schema.addToSchema((0, graphql_1.printSchema)(gqlSchema, {
        commentDescriptions: true,
    }));
    return schema;
};
exports.loadSchemas = loadSchemas;

loadSchemas.ts

import * as appSync from '@aws-cdk/aws-appsync';
import {
  extendSchema,
  GraphQLSchema,
  parse as parseGql,
  printSchema,
  Source,
} from 'graphql';
import type { DocumentNode } from 'graphql';
import { join } from 'path';
import { readFileSync } from 'fs';

const loop = (
  documents: DocumentNode[],
  schema: GraphQLSchema,
): GraphQLSchema => {
  if (documents.length <= 0) {
    return schema;
  }

  const types = schema.getTypeMap();
  // This iteration, only include documents that either only add new types or extend existing types.
  const documentsToInclude = documents.filter(
    (d) =>
      d.definitions.find(
        (def) =>
          (def.kind === 'EnumTypeExtension' ||
            def.kind === 'InputObjectTypeExtension' ||
            def.kind === 'InterfaceTypeExtension' ||
            def.kind === 'ObjectTypeExtension' ||
            def.kind === 'ScalarTypeExtension' ||
            def.kind === 'UnionTypeExtension') &&
          !(def.name.value in types),
      ) == null,
  );
  if (documentsToInclude.length === 0) {
    const dependencies = JSON.stringify(
      documents.map((d) => d.loc?.source.name),
    );
    throw new Error(
      `Unable to load schemas, possible circular dependency found: ${dependencies}`,
    );
  }
  const remainingDocuments = documents.filter(
    (v) => !documentsToInclude.includes(v),
  );

  return loop(
    remainingDocuments,
    documentsToInclude.reduce((acc, v) => extendSchema(acc, v), schema),
  );
};

/**
 * Loads a set of graphql schema files into an AppSync schema.
 *
 * The order of graphql input schemas doesn't matter, this will load them in an order that just works.
 *
 * @param pluginDirs A list of folders with schema files in them.
 * @returns
 */
export const loadSchemas = (pluginDirs: string[]): appSync.Schema => {
  const partialSchemas = pluginDirs.map((f) =>
    parseGql(
      new Source(
        readFileSync(join(f, 'schema.graphql')).toString('utf-8'),
        join(f, 'schema.graphql'),
      ),
    ),
  );

  const gqlSchema = loop(partialSchemas, new GraphQLSchema({}));

  const schema = new appSync.Schema();
  schema.addToSchema('schema { query: Query }');
  schema.addToSchema(
    printSchema(gqlSchema, {
      commentDescriptions: true,
    }),
  );

  return schema;
};