feat(gatsby): graphql engine

[vladar]

Description

This feature is disabled by default. Only available when building gatsby itself with COMPILER_OPTIONS="GATSBY_MAJOR=4"

The new experimental feature: standalone graphql engine (can be required in any node script to run GraphQL queries). Bundles all necessary dependencies using webpack and uses underlying lmdb datastore to access data.

Example usage (after initial gatsby build):

const { GraphQLEngine } = require(`./.cache/query-engine`);

const graphqlEngine = new GraphQLEngine({
  dbPath: `${__dirname}/.cache/data/datastore`,
});

async function run() {
  const variables = {}
  const query = `
  {
    site {
      siteMetadata {
        title
      }
    }
  }
  `;
  const result = await graphqlEngine.runQuery(query, variables);
  console.log(result)
}

run().catch(console.error)

[ch37492]

[wardpeet]

I added a bunch of comments, mostly for clarification as I'm not familiar with the code of this feature. If you feel that some comments should be handled in a follow-up to get this shipped, I'm 100% ok with that.

[wardpeet]

we usually don't use process.cwd() perhaps we need a global getter for program.directory?

[vladar]

We do it all over the place in the codebase. I think it makes sense to add such utility and refactor in a separate PR.

[wardpeet]

LGTM!

[simonjoom]

This feature seems very useful for Gatsby.

Does somebody can make a useful test-case example for the doc to understand the power of this feature?

I thought to get the generation pages' data on backend-side with graphql-engine from the browser via a simple js fetch api call which will display a list of all the available images generated by the website by example (with maybe on action-click on an image displaying size and image infos)

all that without any graphql code generated and bundled like before.

.. some other thoughts?

[ascorbic]

@simonjoom This is an internal feature designed to be used during SSR and DSG, rather than something designed for use elsewhere. I made a proof of concept, but it's not something for production: https://github.com/netlify/gatsby-4-demo/blob/main/example/functions/graphql/graphql.ts