rescue_from handler return values during argument coercion are passed to resolve as the argument's value

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  • #5837 di @austinjb32 — integrata

Valutazione

Difficoltà
3/5
Tempo stimato
1-2 giorni
Idoneità per principianti
58/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
ruby
Ambito
backend-api-design

Direzione di ricerca

Start in Schema::Argument#coerce_into_values and trace the three handle_or_reraise call sites, then check how coerce_arguments and Runtime#evaluate_selection_with_args handle errors. Reproduce with the provided schema and argument validation example. Done means a returned GraphQL::ExecutionError reaches the response as the expected error and the resolver does not receive it as an argument; add a regression test for that behavior.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Describe the bug

When an error is raised during argument coercion — e.g. an argument validates: check failing inside Schema::Argument#prepare_value — the error is routed through handle_or_reraise, and the schema's rescue_from handler's return value is stored as the argument's value. If the handler returns a GraphQL::ExecutionError (a very common pattern), that error object is passed to the field's resolver as the argument value instead of short-circuiting resolution with the error.

Runtime#evaluate_selection_with_args only short-circuits when resolved_arguments itself is an ExecutionError/UnauthorizedError — errors nested inside the Arguments object sail through.

Versions

graphql 2.6.13 (also reproduced on 2.5.11)

Steps to reproduce

require "graphql"

class LeakySchema < GraphQL::Schema
  # Common pattern: rescue_from returns (rather than raises) an error object
  rescue_from(StandardError) do |err, _obj, _args, _ctx, _field|
    GraphQL::ExecutionError.new(err.message)
  end

  class Query < GraphQL::Schema::Object
    field :check, Integer, null: true do
      argument :limit, Integer, validates: { numericality: { within: 1..50 } }
    end

    def check(limit:)
      limit + 1
    end
  end

  query(Query)
end

pp LeakySchema.execute("{ check(limit: 0) }").to_h

Expected behavior

{"errors" => [{"message" => "limit must be within 1..50", ...}], "data" => {"check" => nil}}

Actual behavior

resolve receives the GraphQL::ExecutionError instance as limit, so limit + 1 raises NoMethodError, which the handler then converts into a misleading error:

{"errors" => [{"message" => "undefined method '+' for an instance of GraphQL::ExecutionError", ...}]}

Without any rescue_from handler, the error reraises and surfaces correctly — so this only reproduces on schemas that register a handler which returns an error object. (It also makes the behavior environment-dependent if the handler is registered conditionally, e.g. only outside development.)

Diagnosis

Schema::Argument#coerce_into_values rescues coercion errors via context.schema.handle_or_reraise(context, err) at all three call sites (type.coerce_input, prepare_value, load_and_authorize_value) and assigns the return value as the argument value:

prepared_value = begin
  prepare_value(parent_object, resolved_coerced_value, context: context)
rescue StandardError => err
  context.schema.handle_or_reraise(context, err) # <= a returned error object lands here
end

coerce_arguments correctly handles raised errors (finished_args = err → continue_value), but nothing handles handler-returned ones.

Possible fix

Re-raise the handled result when it's an error object, so coerce_arguments short-circuits with it — I've got a working branch with a failing test + fix here if useful: https://github.com/austinjb32/graphql-ruby/tree/fix-argument-validation-error-leak

Additional context

Same bug family as the historical prepare:-returns-error leak (#1024).

Lingua principale
Ruby
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