# `hops-graphql`

[![npm](https://img.shields.io/npm/v/hops-graphql/next.svg)](https://www.npmjs.com/package/hops-graphql)

This is a [preset for Hops](https://github.com/xing/hops/tree/master#presets) that can be used to set up an `<ApolloProvider />` and enable server-side and client-side support for GraphQL via the Apollo framework.

### Installation

_This preset must be used together with the `hops-react` preset._

Add this preset and its peer dependencies `graphql-tag` and `react-apollo` to your existing Hops React project:

```bash
$ yarn add hops-graphql@next graphql-tag react-apollo
# OR npm install --save hops-graphql@next graphql-tag react-apollo
```

If you don't already have an existing Hops project read this section [on how to set up your first Hops project.](https://github.com/xing/hops/tree/master#quick-start)

### GraphQL Mock Server

Read the [Read Me](./mock-server/README.md) for setup instructions.

### CLI

#### `graphql introspect`

Extract information to support the `IntrospectionFragmentMatcher` from either a remote GraphQL server or from a local GraphQL schema file.

This preset takes care of setting up the Apollo cache and fragment matchers - if a `fragmentsFile` is present it will use the `IntrospectionFragmentMatcher`, otherwise it will fall back to a `HeuristicFragmentMatcher`.

This is not strictly necessary but is recommended if you have a more complex schema and are querying fragments on unions or interfaces.

Head over to https://github.com/apollographql/react-docs/blob/master/source/initialization.md#using-fragments-on-unions-and-interfaces to read more details about this.

##### Arguments

###### `-H` / `--header`

Pass additional HTTP headers that should be sent when executing the introspection query against a remote GraphQL server. For example when your server requires an authentication token or similar.

This argument can be specified multiple times to add multiple HTTP headers.

### Usage

In order to start using GraphQL in your application install this preset and configure the required options (see below).

Check out this [integration test](https://github.com/xing/hops/tree/master/packages/spec/integration/graphql) as an example for how to use this preset.

### Configuration

#### Preset Options

| Name                     | Type      | Default                        | Required | Description                                                              |
| ------------------------ | --------- | ------------------------------ | -------- | ------------------------------------------------------------------------ |
| `fragmentsFile`          | `String`  | `<rootDir>/fragmentTypes.json` | _no_     | Where to store the generated fragment types file                         |
| `graphqlSchemaFile`      | `String`  | `''`                           | _no_     | Path to your GraphQL schema file                                         |
| `graphqlUri`             | `String`  | `''`                           | _yes_    | Url to your GraphQL endpoint                                             |
| `shouldPrefetchOnServer` | `Boolean` | `true`                         | _no_     | Whether Hops should execute GraphQL queries during server-side rendering |

##### `fragmentsFile`

This option controls where the fragment type information that are used for the `IntrospectionFragmentMatcher` should be saved.

By default executing `$ hops graphql introspect` will create a file called `fragmentTypes.json` in the application root directory.

```json
"hops": {
  "fragmentsFile": "<rootDir>/fragmentTypes.json"
}
```

##### `graphqlSchemaFile`

In case your GraphQL server (configured via [`graphqlUri`](#graphqluri)) does not answer to introspection queries, you can provide the full schema as a file from which the introspection fragment matcher can generate information about unions and interfaces.

```json
"hops": {
  "graphqlSchemaFile": "<rootDir>/schema.graphql"
}
```

##### `graphqlUri`

This is the full uri to your GraphQL endpoint which should be used by the client- and server-side when executing requests.

This will also be used to generate fragment type information with `$ hops graphql introspect` in case no [`graphqlSchemaFile`](#graphqlschemafile) has been provided.

```json
"hops": {
  "graphqlUri": "https://www.graphqlhub.com/graphql"
}
```

##### `shouldPrefetchOnServer`

Whether you want "full server-side rendering" or just "app shell" rendering.

This option controls whether you want Hops to execute GraphQL queries during server-side rendering, so that the actual components with actual data will get rendered (if set to false, Hops will not fetch data during server-side rendering).

```json
"hops": {
  "shouldPrefetchOnServer": false
}
```

#### Render Options

This preset has only a single runtime option which can be passed to the `render()` options inside the `styled` key (see example above).

| Name            | Type          | Default               | Required | Description                     |
| --------------- | ------------- | --------------------- | -------- | ------------------------------- |
| `graphql.link`  | `ApolloLink`  | `ApolloHttpLink`      | _no_     | An instance of a `apollo-link`  |
| `graphql.cache` | `ApolloCache` | `ApolloCacheInMemory` | _no_     | An instance of a `apollo-cache` |

##### `link`

By default this preset creates an `HttpLink` with the configured [`graphqlUri`](#graphqluri). If you need a different link, you can pass the instantiated link to the render options.

Read more about Apollo links here:

- https://www.apollographql.com/docs/link/
- https://www.apollographql.com/docs/react/advanced/network-layer.html

```javascript
export default render(<MyApp />, {
  graphql: { link: new HttpLink({ uri: 'http://api.githunt.com/graphql' }) },
});
```

##### `cache`

By default this preset creates an [`InMemoryCache`](https://www.apollographql.com/docs/react/advanced/caching.html) which uses either the [`IntrospectionFragmentMatcher` or `HeuristicFragmentMatcher`](https://www.apollographql.com/docs/react/advanced/fragments.html#fragment-matcher) depending on whether fragment introspection results are available or not (create them with [`$ hops graphql introspect`](#graphql-introspect)).

In case you need to configure a different Apollo cache you can pass an instantiated cache to the render options.

Read more about Apollo caches here: https://www.apollographql.com/docs/react/advanced/caching.html#configuration

```javascript
export default render(<MyApp />, {
  graphql: {
    cache: new InMemoryCache(),
  },
});
```

### Mixin Hooks API

#### `getApolloLink(): ApolloLink` ([override](https://github.com/untool/mixinable/blob/master/README.md#defineoverride))

Hook to return a custom [ApolloLink](https://github.com/apollographql/apollo-link).

Useful when the link needs access to the current request object, which only exists in the mixin context.

Beware that `link` passed as render option takes precedence.

#### `getApolloCache(): ApolloCache` ([override](https://github.com/untool/mixinable/blob/master/README.md#defineoverride))

Hook to return a custom [ApolloCache](https://www.apollographql.com/docs/react/advanced/caching.html).

### `createFragmentMatcher` ([override](https://github.com/untool/mixinable/blob/master/README.md#defineoverride))

Allows to get the [fragment matcher](https://www.apollographql.com/docs/react/advanced/fragments.html) that needs to be passed to the `ApolloCache`. Useful if you plan to override `getApolloCache`.

#### `shouldPrefetchOnServer(): boolean` ([override](https://github.com/untool/mixinable/blob/master/README.md#defineoverride))

This is an overrideable hook that can be used to customize the behavior of when Hops should prefetch data during server-side rendering. E.g. execute GraphQL queries during initial render.

By default it returns whatever is configured in the [`shouldPrefetchOnServer` preset option](#shouldprefetchonserver) or `true` if the config is not set.

In case you need more control over the server-side rendering you can implement this method and provide your own implementation that decides if data should be prefetched during server-side rendering.