implement-graphql

Implement GraphQL

Use this skill when designing, implementing, or reviewing GraphQL APIs in a Rails application with the graphql-ruby gem.

Core Process

DO NOT proceed to step 3 before step 1 is written and failing.

SPEC: Write failing spec (happy path + auth + validation error case) — see TESTING.md. Use AppSchema.execute in spec/graphql/. Never use HTTP controller dispatch for GraphQL specs.
TYPE: Define arguments and return types. Use connection_type for pagination shapes. Do not leak internal model names.
IMPLEMENT: Create resolver/mutation class delegating to a service object. Use dedicated classes instead of inline field blocks.

N+1 CHECK: Use dataloader on every association load. For list resolvers, prime the dataloader with the records returned by the relation before fields resolve associated objects. Use bullet and db-query-matchers in specs.
```
# ✅ batches loads across all records
def buyer
  dataloader.with(Sources::RecordById, Buyer).load(object.buyer_id)
end
```

AUTH CHECK: Apply field-level guards where data is sensitive using Pundit or custom context guards.

field :internal_notes, String, null: true do
  guard -> (_obj, _args, ctx) { ctx[:current_user]&.admin? }
end

FINAL CHECK: Verify every item in the HARD-GATE checklist below. Ensure mutations return { result, errors } shapes on failure.
```
rescue ActiveRecord::RecordInvalid => e
  { order: nil, errors: e.record.errors.full_messages }
```
RUN: Ensure the full test suite is green before PR.

Before shipping a resolver/mutation slice, ALL of the following must be confirmed:

Specs — covers happy path, unauthenticated, unauthorized, validation errors, N+1 counts, and schema limits.
N+1 Prevention — dataloader.with(Source, Model).load(id) on every association; never object.association.
Dataloader Priming — collection resolvers prime records before association fields resolve.
Authorization — sensitive fields have field-level guards (not type-level alone).
Type Conventions — paginated collections use Types::*Type.connection_type, not plain arrays.
Schema Safeguards — introspection disabled in production; max_depth and max_complexity set.
Error Handling — mutations return { result, errors } with rescue blocks; no unhandled exceptions.
Documentation — description: on every field in every type.
Resolver Structure — dedicated resolver classes, not inline field blocks.

Load these files only when their specific content is needed:

TESTING.md — For the spec template, paths, and checklist.
EXAMPLES.md — For detailed code examples of dataloaders, mutations, and types.

Skill	When to chain
define-domain-language	Type and field naming must match business language
plan-tests	Choose first failing spec (mutation vs query vs resolver unit)
write-tests	Full TDD cycle for resolvers and mutations
security-check	Auth, introspection disable, query depth/complexity limits