Dancer2::Plugin::GraphQL - a plugin for adding GraphQL route handlers

package MyWebApp;

use Dancer2;
use Dancer2::Plugin::GraphQL;
use GraphQL::Schema;

my $schema = GraphQL::Schema->from_doc(<<'EOF');
schema {
  query: QueryRoot
}
type QueryRoot {
  helloWorld: String
}
EOF
graphql '/graphql' => $schema, { helloWorld => 'Hello, world!' };

dance;

# OR, equivalently:
graphql '/graphql' => $schema => sub {
  my ($app, $body, $execute) = @_;
  # returns JSON-able Perl data
  $execute->(
    $schema,
    $body->{query},
    undef, # $root_value
    $app->request->headers,
    $body->{variables},
    $body->{operationName},
    undef, # $field_resolver
  );
};

# OR, with bespoke user-lookup and caching:
graphql '/graphql' => sub {
  my ($app, $body, $execute) = @_;
  my $user = MyStuff::User->lookup($app->request->headers->header('X-Token'));
  die "Invalid user\n" if !$user; # turned into GraphQL { errors => [ ... ] }
  my $cached_result = MyStuff::RequestCache->lookup($user, $body->{query});
  return $cached_result if $cached_result;
  MyStuff::RequestCache->cache_and_return($execute->(
    $schema,
    $body->{query},
    undef, # $root_value
    $user, # per-request info
    $body->{variables},
    $body->{operationName},
    undef, # $field_resolver
  ));
};

The graphql keyword which is exported by this plugin allow you to define a route handler implementing a GraphQL endpoint.

Parameters, after the route pattern. The first three can be replaced with a single array-ref. If so, the first element is a classname-part, which will be prepended with "GraphQL::Plugin::Convert::". The other values will be passed to that class's "to_graphql" in GraphQL::Plugin::Convert method. The returned hash-ref will be used to set options.

E.g.

graphql '/graphql' => [ 'Test' ]; # uses GraphQL::Plugin::Convert::Test

• $schema

  A GraphQL::Schema object.

• $root_value

  An optional root value, passed to top-level resolvers.

• $field_resolver

  An optional field resolver, replacing the GraphQL default.

• $route_handler

  An optional route-handler, replacing the plugin's default - see example above for possibilities.

  It must return JSON-able Perl data in the GraphQL format, which is a hash with at least one of a data key and/or an errors key.

  If it throws an exception, that will be turned into a GraphQL-formatted error.

If you supply two code-refs, they will be the $resolver and $handler. If you only supply one, it will be $handler. To be certain, pass all four post-pattern arguments.

The route handler code will be compiled to behave like the following:

• Passes to the GraphQL execute, possibly via your supplied handler, the given schema, $root_value and $field_resolver.
• The action built matches POST / GET requests.
• Returns GraphQL results in JSON form.

By default the plugin will not return GraphiQL, but this can be overridden with plugin setting 'graphiql', to true.

Here is example to use GraphiQL:

plugins:
  GraphQL:
    graphiql: true

Ed J

Based heavily on Dancer2::Plugin::Ajax by "Dancer Core Developers".

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.