Usage Examples¶

Hint

Many of the following examples make use of GitHub GraphQL API. You can retrieve a token as detailed here.

Queries¶

Simple Query¶

The aiographql.client.GraphQLClient can be used to store headers like Authorization that need to be sent with every request made.

client = GraphQLClient(
    endpoint="https://api.github.com/graphql",
    headers={"Authorization": f"Bearer {TOKEN}"},
)
request = GraphQLRequest(
    query="""
        query {
          viewer {
            login
          }
        }
    """
)
response = await client.query(request=request)

If you have a valid token, the above query will return the following data.

>>> response.data
{'viewer': {'login': 'username'}}

If you intend to only make use of the query once, ie. it is not re-used, you may forgo the creation of an aiographql.client.GraphQLRequest instance and pass in the query string direct to aiographql.client.GraphQLClient.query().

await client.query(request="{ viewer { login } }")

Query Variables¶

request = GraphQLRequest(
    query="""
        query($number_of_repos:Int!) {
          viewer {
             repositories(last: $number_of_repos) {
               nodes {
                 name
                 isFork
               }
             }
           }
        }
    """,
    variables={"number_of_repos": 3},
)
response: GraphQLResponse = await client.query(request=request)

You can override default values specified in the prepared request too. The values are upserted into the existing defaults.

response: GraphQLResponse = await client.query(request=request, variables={
    "number_of_repos": 1
})

Specifying Operation Name¶

You can use a single aiographql.client.GraphQLRequest object to stop a query wit multiple operations.

request = GraphQLRequest(
    query="""
        query FindFirstIssue {
          repository(owner:"octocat", name:"Hello-World") {
            issues(first:1) {
              nodes {
                id
                url
              }
            }
          }
        }

        query FindLastIssue {
          repository(owner:"octocat", name:"Hello-World") {
            issues(last:1) {
              nodes {
                id
                url
              }
            }
          }
        }
    """,
    operation="FindFirstIssue",
)

# use the default operation (FindFirstIssue)
response = await client.query(request=request)

# use the operation FindLastIssue
response = await client.query(
    request=request,
    operation="FindLastIssue"
)

Subscriptions¶

The following example makes use of the Hasura World Database Demo application as there aren’t many public GraphQL schema that allow subscriptions for testing. You can use the project’s provided docker compose file to start an instance locally.

By default the subscription is closed if any of the following event type is received.

aiographql.client.GraphQLSubscriptionEventType.ERROR
aiographql.client.GraphQLSubscriptionEventType.CONNECTION_ERROR
aiographql.client.GraphQLSubscriptionEventType.COMPLETE

The following example will subscribe to any change events and print the event as is to stdout when either aiographql.client.GraphQLSubscriptionEventType.DATA or aiographql.client.GraphQLSubscriptionEventType.ERROR is received.

request = GraphQLRequest(
    query="""
    subscription {
      city(where: {name: {_eq: "Berlin"}}) {
        name
        id
      }
    }
"""
)
# subscribe to data and error events, and print them
subscription = await client.subscribe(
    request=request, on_data=print, on_error=print
)
# unsubscribe
await subscription.unsubscribe_and_wait()

Hint

In the case you want to specify the GraphQL over WebSocket sub-protocol to use, you may do so by setting aiographql.client.GraphQLSubscription.protocols. For example, await client.subscribe(..., protocols="graphql-ws"). This is required for certain server implementations like Apollo Server as it supports multiple implementations.

Callback Registry¶

Subscriptions make use of cafeteria.asyncio.callbacks.CallbackRegistry internally to trigger registered callbacks when an event of a particular type is encountered. You can also register a Coroutine if required.

# both the following statements have the same effect
subscription = await client.subscribe(
    request=request, on_data=print, on_error=print
)
subscription = await client.subscribe(
    request=request, callbacks={
        GraphQLSubscriptionEventType.DATA: print,
        GraphQLSubscriptionEventType.ERROR: print,
    }
)

# this can also be done as below
registry = CallbackRegistry()
registry.register(GraphQLSubscriptionEventType.DATA, print)
registry.register(GraphQLSubscriptionEventType.ERROR, print)

If you’d like a single callback for all event types or any “unregistered” event, you can simply set the event type to None when registering the callback.

>>> registry.register(None, print)

Here is an example that will print the timestamp every time a keep-alive event is received.

subscription.callbacks.register(
    GraphQLSubscriptionEventType.KEEP_ALIVE,
    lambda x: print(f"Received keep-alive at {datetime.utcnow().isoformat()}")
)

Validation¶

Client Side Query Validation¶

Because we make use of GraphQL Core 3, client-side query validation is performed by default.

request = GraphQLRequest(
    query="""
        query {
          bad {
            login
          }
        }
    """
)
response: GraphQLResponse = await client.query(request=request)

This will raise aiographql.client.GraphQLClientValidationException. The message will also contain information about the error.

aiographql.client.exceptions.GraphQLClientValidationException: Query validation failed

Cannot query field 'bad' on type 'Query'.

GraphQL request:3:15
2 |             query {
3 |               bad {
  |               ^
4 |                 login

Process finished with exit code 1

Server Side Query Validation¶

You can skip the client side validation, forcing server side validation instead by setting the aiographql.client.GraphQLRequest.validate to False before making the request.

request = GraphQLRequest(
    query="""
        query {
          bad {
            login
          }
        }
    """,
    validate=False
)
response: GraphQLResponse = await client.query(request=request)

>>> response.data
{}
>>> response.errors
[GraphQLError(extensions={'code': 'undefinedField', 'typeName': 'Query', 'fieldName': 'bad'}, locations=[{'line': 3, 'column': 15}], message="Field 'bad' doesn't exist on type 'Query'", path=['query', 'bad'])]