Schema stitching in GrAMPS with two external data sources.

*schema-stitching-in-graphql-with-gramps.md

Schema Stitching in GrAMPS Using External Data Sources

In this example, we install two GrAMPS data sources from npm, then extend the schema to allow one data source to access data on the other.

.babelrc

{
  "presets": [
    [
      "@babel/preset-env",
      {
        "targets": { "node": "6" },
        "shippedProposals": true,
        "useBuiltIns": "usage"
      }
    ]
  ]
}

gateway.js

import Express from "express";
import getPort from "get-port";
import bodyParser from "body-parser";
import { prepare } from "@gramps/gramps";
import { GraphQLSchema } from "graphql";
import { mergeSchemas } from "graphql-tools";
import { graphqlExpress, graphiqlExpress } from "apollo-server-express";

// Data sources
import XKCD from "@gramps/data-source-xkcd";
import Numbers from "@gramps/data-source-numbers";

const gramps = prepare({
  dataSources: [XKCD, Numbers]
});

const linkTypeDefs = `
  extend type XKCD_Comic {
    numbers: Numbers_Trivia
  }
`;

const schema = mergeSchemas({
  schemas: [gramps.schema, linkTypeDefs],
  resolvers: mergeInfo => ({
    XKCD_Comic: {
      numbers: {
        fragment: `fragment XKCDFragment on XKCD_Comic { num }`,
        resolve: (parent, args, context, info) => {
          return mergeInfo.delegate(
            "query",
            "trivia",
            { number: parent.num },
            context,
            info
          );
        }
      }
    }
  })
});

const app = new Express();

app.use(bodyParser.json());
app.use(
  "/graphql",
  graphqlExpress({
    schema,
    context: gramps.context
  })
);
app.use("/graphiql", graphiqlExpress({ endpointURL: "/graphql" }));

async function startServer(app) {
  const PORT = await getPort(8080);
  app.listen(PORT, () => {
    console.log(`\n=> http://localhost:${PORT}/graphiql`);
  });
}

startServer(app);

package.json

{
  "name": "gramps-stitching-external",
  "version": "1.0.0",
  "main": "index.js",
  "author": "Jason Lengstorf (https://lengstorf.com) <jason@lengstorf.com>",
  "license": "MIT",
  "scripts": {
    "start": "nodemon -e js,json,graphql index.js --exec babel-node",
    "build": "babel index.js -d dist",
    "predev": "yarn build",
    "dev": "gramps dev -d ../../gramps-graphql/data-source-base -g dist"
  },
  "dependencies": {
    "@gramps/data-source-numbers": "^1.0.0-beta3",
    "@gramps/data-source-xkcd": "^1.0.3-beta4",
    "@gramps/gramps": "^1.2.0",
    "apollo-server-express": "^1.3.2",
    "body-parser": "^1.18.2",
    "express": "^4.16.2",
    "get-port": "^3.2.0",
    "graphql": "^0.12.3",
    "graphql-tools": "^2.18.0"
  },
  "devDependencies": {
    "@babel/cli": "^7.0.0-beta.37",
    "@babel/core": "^7.0.0-beta.37",
    "@babel/preset-env": "^7.0.0-beta.37",
    "@gramps/cli": "^1.1.4",
    "nodemon": "^1.14.11"
  }
}