class GraphQL::StaticValidation::VariablesAreUsedAndDefined
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`
Public Instance Methods
validate(context)
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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_hash()
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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
Private Instance Methods
create_errors(node_variables, context)
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Determine all the error messages, Then push messages into the validation context
# File lib/graphql/static_validation/rules/variables_are_used_and_defined.rb, line 131 def create_errors(node_variables, context) # Declared but not used: node_variables .select { |name, usage| usage.declared? && !usage.used? } .each { |var_name, usage| context.errors << message("Variable $#{var_name} is declared by #{usage.declared_by.name} but not used", usage.declared_by, path: usage.path) } # Used but not declared: node_variables .select { |name, usage| usage.used? && !usage.declared? } .each { |var_name, usage| context.errors << message("Variable $#{var_name} is used by #{usage.used_by.name} but not declared", usage.ast_node, path: usage.path) } end
follow_spreads(node, parent_variables, spreads_for_context, fragment_definitions, visited_fragments)
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Follow spreads in `node`, looking them up from `spreads_for_context` and finding their match in `fragment_definitions`. Use those fragments to update {VariableUsage}s in `parent_variables`. Avoid infinite loops by skipping anything in `visited_fragments`.
# File lib/graphql/static_validation/rules/variables_are_used_and_defined.rb, line 101 def follow_spreads(node, parent_variables, spreads_for_context, fragment_definitions, visited_fragments) spreads = spreads_for_context[node] - visited_fragments spreads.each do |spread_name| def_node = nil variables = nil # Implement `.find` by hand to avoid Ruby's internal allocations fragment_definitions.each do |frag_def_node, vars| if frag_def_node.name == spread_name def_node = frag_def_node variables = vars break end end next if !def_node visited_fragments << spread_name variables.each do |name, child_usage| parent_usage = parent_variables[name] if child_usage.used? parent_usage.ast_node = child_usage.ast_node parent_usage.used_by = child_usage.used_by parent_usage.path = child_usage.path end end follow_spreads(def_node, parent_variables, spreads_for_context, fragment_definitions, visited_fragments) end end