Troubleshooting

# WRONG
fullName: firstName + " " + lastName

# CORRECT
fullName: $([firstName, lastName])->joinNotNull(' ')

# With more parts
address: $([street, city, state, zip])->joinNotNull(', ')

# WRONG - Will not compose
body: "{ userId: $args.id }"
greeting: "Hello"
count: 42

# CORRECT
body: "$({ userId: $args.id })"
greeting: $("Hello")
count: $(42)
isActive: $(true)

# WRONG
firstItem: items[0]
thirdItem: items[2]

# CORRECT
firstItem: items->first
lastItem: items->last
thirdItem: items->get(2)
firstThree: items->slice(0, 3)

Error: MISSING_ENTITY_CONNECTOR
Entity "User" is missing a connector.

# Add @connect to make it a resolvable entity
type User @connect(
  source: "api"
  http: { GET: "/users/{$this.id}" }
  selection: "id name email"
) {
  id: ID!
  name: String
  email: String
}

Error: INVALID_BODY
Body must use literal syntax.

# WRONG
body: "{ userId: $args.id }"

# CORRECT
body: "$({ userId: $args.id })"

# For nested objects
body: "$({ user: { id: $args.id, name: $args.name } })"

# WRONG
isActive: status == "active"
is200: $status == 200

# CORRECT
isActive: status->eq("active")
is200: $status->eq(200)

# For DELETE operations that should return true on success
selection: "$(true)"

# WRONG
result: condition ? valueA : valueB

# Use ?? for null/undefined fallback
result: value ?? "default"

# Use ?! for undefined-only fallback (preserves null)
result: value ?! "fallback"

# Use ->match for value mapping
result: status->match(
  ["active", "Active User"],
  ["inactive", "Inactive User"],
  [@, "Unknown"]
)

# WRONG - @ changes meaning in nested method
items: $.list->filter(@.active->and(@.price->gt(10)))

# CORRECT - Chain filters
items: $.list->filter(@.active)->filter(@.price->gt(10))

# For find
item: $.list->filter(@.active)->find(@.price->gt(10))

Error: Circular reference detected between Product and Review

type Product {
  id: ID!
  reviews: [Review] @connect(
    http: { GET: "/products/{$this.id}/reviews" }
    selection: "id rating text productId"  # Include FK
  )
}

type Review {
  id: ID!
  rating: Int
  text: String
  productId: ID! @inaccessible  # Hide from clients
  product: Product @connect(
    http: { GET: "/products/{$this.productId}" }
    selection: "id name"
  )
}

# WRONG - Headers are arrays
auth: $request.headers.authorization

# CORRECT
auth: $request.headers.authorization->first

# For headers with special characters
custom: $request.headers.'x-custom-header'->first

# WRONG - Unnecessary
selection: """
$ {
  id
  name
}
"""

# CORRECT
selection: """
id
name
"""

Error: Incompatible federation and connect versions

# CORRECT - Always use these versions together
extend schema
  @link(url: "https://specs.apollo.dev/federation/v2.12")
  @link(url: "https://specs.apollo.dev/connect/v0.3", import: ["@source", "@connect"])

# If there's no /address/{id} endpoint, don't make it an entity
type Address {  # No @connect, no @key
  street: String
  city: String
  country: String
}

# Include it inline in the parent's selection
type User @connect(
  http: { GET: "/users/{$this.id}" }
  selection: """
  id
  name
  address {
    street
    city
    country
  }
  """
) {
  id: ID!
  name: String
  address: Address
}

# apiResponseBody from REST API
apiResponseBody: |
  { "user_id": "123", "user_name": "Alice" }

# Selection mapping
selection: """
id: user_id
name: user_name
"""

# connectorResponse is the mapping result
connectorResponse: |
  { "id": "123", "name": "Alice" }

# Non-batch (N+1)
type Product @connect(
  http: { GET: "/products/{$this.id}" }
  selection: "id name"
) {
  id: ID!
  name: String
}

# Batch (requires API support)
type Product @connect(
  http: {
    POST: "/products/batch"
    body: "ids: $batch.id"
  }
  selection: "id name"
) {
  id: ID!
  name: String
}