Class: GraphQL::StaticValidation::VariablesAreUsedAndDefined

Inherits:
Object
  • Object
show all
Includes:
Message::MessageHelper
Defined in:
lib/graphql/static_validation/rules/variables_are_used_and_defined.rb

Overview

The problem is

  • Variable usage must be determined at the OperationDefinition level
  • You can't tell how fragments use variables until you visit FragmentDefinitions (which may be at the end of the document)

So, this validator includes some crazy logic to follow fragment spreads recursively, while avoiding infinite loops.

graphql-js solves this problem by:

  • re-visiting the AST for each validator
  • allowing validators to say followSpreads: true

Defined Under Namespace

Classes: VariableUsage

Instance Method Summary collapse

Methods included from Message::MessageHelper

#message

Instance Method Details

#validate(context) ⇒ Object


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# File 'lib/graphql/static_validation/rules/variables_are_used_and_defined.rb', line 31

def validate(context)
  variable_usages_for_context = Hash.new {|hash, key| hash[key] = variable_hash }
  spreads_for_context = Hash.new {|hash, key| hash[key] = [] }
  variable_context_stack = []

  # OperationDefinitions and FragmentDefinitions
  # both push themselves onto the context stack (and pop themselves off)
  push_variable_context_stack = ->(node, parent) {
    # initialize the hash of vars for this context:
    variable_usages_for_context[node]
    variable_context_stack.push(node)
  }

  pop_variable_context_stack = ->(node, parent) {
    variable_context_stack.pop
  }


  context.visitor[GraphQL::Language::Nodes::OperationDefinition] << push_variable_context_stack
  context.visitor[GraphQL::Language::Nodes::OperationDefinition] << ->(node, parent) {
    # mark variables as defined:
    var_hash = variable_usages_for_context[node]
    node.variables.each { |var|
      var_usage = var_hash[var.name]
      var_usage.declared_by = node
      var_usage.path = context.path
    }
  }
  context.visitor[GraphQL::Language::Nodes::OperationDefinition].leave << pop_variable_context_stack

  context.visitor[GraphQL::Language::Nodes::FragmentDefinition] << push_variable_context_stack
  context.visitor[GraphQL::Language::Nodes::FragmentDefinition].leave << pop_variable_context_stack

  # For FragmentSpreads:
  #  - find the context on the stack
  #  - mark the context as containing this spread
  context.visitor[GraphQL::Language::Nodes::FragmentSpread] << ->(node, parent) {
    variable_context = variable_context_stack.last
    spreads_for_context[variable_context] << node.name
  }

  # For VariableIdentifiers:
  #  - mark the variable as used
  #  - assign its AST node
  context.visitor[GraphQL::Language::Nodes::VariableIdentifier] << ->(node, parent) {
    usage_context = variable_context_stack.last
    declared_variables = variable_usages_for_context[usage_context]
    usage = declared_variables[node.name]
    usage.used_by = usage_context
    usage.ast_node = node
    usage.path = context.path
  }


  context.visitor[GraphQL::Language::Nodes::Document].leave << ->(node, parent) {
    fragment_definitions = variable_usages_for_context.select { |key, value| key.is_a?(GraphQL::Language::Nodes::FragmentDefinition) }
    operation_definitions = variable_usages_for_context.select { |key, value| key.is_a?(GraphQL::Language::Nodes::OperationDefinition) }

    operation_definitions.each do |node, node_variables|
      follow_spreads(node, node_variables, spreads_for_context, fragment_definitions, [])
      create_errors(node_variables, context)
    end
  }
end

#variable_hashObject


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# File 'lib/graphql/static_validation/rules/variables_are_used_and_defined.rb', line 27

def variable_hash
  Hash.new {|h, k| h[k] = VariableUsage.new }
end