Graphql-ruby: Passing empty array in a variable returns an error

[blevine]

The following mutation works as expected:

mutation {
   AdjustRoles(input: {
     role_names: []
   }) {
     clientMutationId
     viewer {
       id  active_role_names
     }
   }
}

However the same mutation using variables:

mutation AdjustRolesMutation($role_names: [String]!) {
  AdjustRoles(input: {
    role_names: $role_names
  }) {
    clientMutationId
    viewer {
      id  active_role_names
    }
  }
}

Variables
{ "role_names": [] }

Causes the following error:

{
  "errors": [
    {
      "message": "Variable role_names of type [String]! was provided invalid value",
      "locations": [
        {
          "line": 1,
          "column": 30
        }
      ],
      "value": null,
      "problems": [
        {
          "path": [],
          "explanation": "Expected value to not be null"
        }
      ]
    }
  ]
}

Looks like the empty array is being treated as null.

[rmosolgo]

Oops 😬

[blevine]

@rmosolgo So this is a confirmed bug then?

[rmosolgo]

Yes, I think so, it seems like [] should be a valid input for [String]!!

[AlexanderMint]

I have received the same mistake

[AlexanderMint]

Сause of error:

GraphQL::Field.define do
  argument :firstName, !types.String
  argument :lastName, !types.String
  argument :email, !types.String
end

query:

mutation SignUp($firstName: String!, $lastName: String!, $email: String!) {
  signUp(firstName: $firstName, lastName: $lastName, email: $email) {
    firstName
  }
}

and variables

{
  "firstName": "name",
  "lastName": "lastName",
  "email": "[email protected]"
}

Problem in the file of a lib/graphql/query/variables.rb, line: 29

# variable_name == "firstName" <- String
# @provided_variables == {:firstName=>"name", :lastName=>"lastName", :email=>"[email protected]"}
provided_value = @provided_variables[variable_name] # result: nil

[rmosolgo]

@AlexanderMint Use string keys for variables, eg

{
  "firstName" => "name",
  "lastName" => "lastName",
  "email" => "[email protected]"
}

(I switched : for =>)

[AlexanderMint]

@rmosolgo But it isn't possible for inquiry json
Variables are invalid JSON: Unexpected token = in JSON at position 16.

[AlexanderMint]

If I am not mistaken, parameters will always be the String type.

{
  "firstName": "name",
  ...
}

And variables names - Symbol

signUp(firstName: $firstName, ...) {

[rmosolgo]

I don't quite understand what you mean, but "something": creates a symbol key, for example:

$ irb
irb(main):001:0> hash = { "some_key": 1 }
# => {:some_key=>1}
irb(main):002:0> hash.keys.first
# => :some_key
irb(main):003:0> hash.keys.first.class
# => Symbol

[AlexanderMint]

@rmosolgo I receive a mistake:

{
  "errors": [
    {
      "message": "Variable firstName of type String! was provided invalid value",
      "locations": [
        {
          "line": 1,
          "column": 17
        }
      ],
      "value": null,
      "problems": [
        {
          "path": [],
          "explanation": "Expected value to not be null"
        }
      ]
    },
    {
      "message": "Variable lastName of type String! was provided invalid value",
      "locations": [
        {
          "line": 1,
          "column": 38
        }
      ],
      "value": null,
      "problems": [
        {
          "path": [],
          "explanation": "Expected value to not be null"
        }
      ]
    },
    {
      "message": "Variable email of type String! was provided invalid value",
      "locations": [
        {
          "line": 1,
          "column": 58
        }
      ],
      "value": null,
      "problems": [
        {
          "path": [],
          "explanation": "Expected value to not be null"
        }
      ]
    }
  ]
}

Query:

mutation SignUp($firstName: String!, $lastName: String!, $email: String!) {
  signUp(firstName: $firstName, lastName: $lastName, email: $email) {
    firstName
  }
}
{
  "firstName": "name",
  "lastName": "lastName",
  "email": "[email protected]"
}

Action:

Schema.execute(params[:query],
               variables: params[:variables] || {},
               context: { user_id: session[:user_id] }).to_json

schema.rb

Schema = GraphQL::Schema.define do
  query Types::QueryType
  mutation Types::MutationType
end

Screenshot: https://imgur.com/VuLLA0s

What do I do not so?

[rmosolgo]

Oh, it looks OK! What do you get if you print out params[:variables], for example

p params[:variables]
# or 
Rails.logger.info(params[:variables])

Can you tell if the keys are present in params[:variables]

?

[AlexanderMint]

@rmosolgo params[:variables]:
{:firstName=>"name", :lastName=>"lastName", :email=>"[email protected]"}

[rmosolgo]

So, the keys are hashes, but you need string keys:

# Prepare a new hash to hold string-keyed variables 
graphql_variables = {} 
# copy each pair into the  new hash, but convert each key to a string with .to_s
params[:variables].each do |k, v|
 graphql_variables[k.to_s] = v 
end 
# Make sure they're strings: 
p graphql_variables 

# then use them: 
Schema.execute(query_str, variables: graphql_variables, ...)

[AlexanderMint]

@rmosolgo Thanks, so everything works. Maybe you will make it in gem?

[rmosolgo]

@blevine Are you still experiencing this issue?

I tried to add a test to find the bug but I couldn't find it, this test passes: https://github.com/rmosolgo/graphql-ruby/compare/fix-empty-list-input

Could you share the Ruby code where you prepare variables and pass them to execute ?

[blevine]

On further investigation I believe that this is not your bug. Looks like Rails is converting the empty array to a nil. See https://github.com/rails/rails/issues/13766 and https://github.com/rails/rails/pull/13188. I haven't been able to disable this behavior via the switch that was added in 4.1.8:

config.action_dispatch.perform_deep_munge = false

but that's my problem to track down. Closing this issue.

[rmosolgo]

Thanks for following up, hope you can track it down!