Improved GraphQL client

[swalkinshaw]

This is a complete rewrite of the GraphQL client functionality.

The previous implementation suffered from a few problems making it virtually unusable as detailed in #511. Here's a summary:

1. you couldn't specify a local schema file
2. due to the above, the client made a dynamic introspection request on initialization which was very slow
3. unbounded memory growth due to building new clients at runtime

This rewrite was focused on solving those problems first and foremost but we also had a few other goals:

• support API versioning
• provide better defaults and an improved developer experience
• ensure it's hard to do the wrong thing

The new GraphQL client only supports loading local schema files to ensure no introspection requests are made during app runtime. The goal is that clients are fully initialized at application boot time (and if you're using Rails this is handled automatically).

Workflow:

1. Set ShopifyAPI::GraphQL.schema_location to a directory path (or use the default in Rails of db/shopify_graphql_schemas).
2. Save a JSON version of Shopify's Admin schema locally (or use the shopify_api:graphql:dump Rake task) to the schema_location and name it after the API version: 2020-01.json.
3. Access the client at ShopifyAPI::GraphQL.client
4. Execute queries via client.query

Rails integration

All the new features are designed to work independently of Rails but there are a few additional integration points:

• schema_location is set to be Rails specific within db/
• the Rake task is loaded automatically with the environment task prerequisite
• clients are initialized during Rails initialization

Migration

If anyone is using the current GraphQL client it's very easy to migrate to this new one.

Previously a client was initialized with ShopifyAPI::GraphQL.new:

client = ShopifyAPI::GraphQL.new

SHOP_NAME_QUERY = client.parse <<-'GRAPHQL'
  {
    shop {
      name
    }
  }
GRAPHQL

result = client.query(SHOP_NAME_QUERY)
result.data.shop.name

Now you use ShopifyAPI::GraphQL.client which has already been initialized:

SHOP_NAME_QUERY = ShopifyAPI::GraphQL.client.parse <<-'GRAPHQL'
  {
    shop {
      name
    }
  }
GRAPHQL

result = ShopifyAPI::GraphQL.client.query(SHOP_NAME_QUERY)
result.data.shop.name

Todo

• Update README

[RobertWSaunders]

This is awesome, I think you can update the GraphQL docs to use your ShopifyAPI::GraphQL.client instead of ShopifyAPI::GraphQL.new. Just saw your PR description TODO. 👏

[tanema]

Looks good to me, I would prefer to have the migration guide and docs on setting up the schema in before we release the version with this functionality in it.

[swalkinshaw]

Updated with:

• README changes
• Full usage output for the rake task
• Documentation guide in docs/graphql.md

👀 appreciated

[swalkinshaw]

@alanhill helped 🎩 this and got it all working upgrading a real app 🎉

With his help we found some issues with the rake task so they've all been fixed now.

[chrisbutcher]

LGTM 🎉