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Type MappingFields

Fields

Field behavior comments and nullability control.

Field Behavior Comments

Proto field comments control nullability and type inclusion:

CommentEffect
// Required.Field is non-nullable (!)
// Output only.Field only in ObjectType, excluded from InputType
// Input only.Field only in InputType, excluded from ObjectType

Comments can be combined:

message User {
  // Required. Output only.
  uint64 id = 1;
 
  // Required.
  string name = 2;
 
  // Input only.
  string password = 3;
 
  // Optional field (no comment)
  string bio = 4;
}
type User {
  id: String!      # Required, included (Output only)
  name: String!    # Required, included
  # password excluded (Input only)
  bio: String      # Nullable
}
 
input UserInput {
  # id excluded (Output only)
  name: String!    # Required, included
  password: String # Included (Input only), nullable without Required
  bio: String      # Nullable
}

Explicit Nullability Control

Override nullability with proto annotations:

Output Nullability

message Example {
  string nullable_field = 1 [(graphql.field).output_nullability = NULLABLE];
  string non_null_field = 2 [(graphql.field).output_nullability = NON_NULL];
}
type Example {
  nullableField: String   # Forced nullable
  nonNullField: String!   # Forced non-null
}

Input Nullability

message Example {
  string field = 1 [(graphql.field).input_nullability = NON_NULL];
}
input ExampleInput {
  field: String!
}

Partial Input Nullability

When using partial_inputs=true:

message Example {
  // Required.
  string always_required = 1 [(graphql.field).partial_input_nullability = NON_NULL];
}
input ExamplePartialInput {
  alwaysRequired: String!  # Stays non-null even in partial input
}

Nullability Values

ValueEffect
NULLABILITY_UNSPECIFIEDUse default behavior
NULLABLEField is nullable
NON_NULLField is non-nullable (!)

Repeated Fields

Repeated fields always generate non-null lists with non-null items:

message Example {
  repeated string tags = 1;
}
type Example {
  tags: [String!]!
}

ID Fields

Use (graphql.field).id = true to use GraphQL ID type:

message User {
  // Required. Output only.
  uint64 id = 1 [(graphql.field).id = true];
}
type User {
  id: ID!
}

Renaming Fields

Override the field name with (graphql.field).name:

message User {
  string user_name = 1 [(graphql.field).name = "name"];
}
type User {
  name: String  # Not userName
}

By default, field names are converted from snake_case to camelCase:

message Example {
  string first_name = 1;  # → firstName
  string lastName = 2;    # → lastName (preserved)
}

Ignoring Fields

Exclude fields from generation:

message User {
  string name = 1;
  string internal_data = 2 [(graphql.field).ignore = true];
}
type User {
  name: String
  # internalData not included
}

Skip Resolver

Omit resolver implementation:

message User {
  string computed_field = 1 [(graphql.field).skip_resolver = true];
}

This generates the field type but skips the resolver, allowing you to implement it manually.

MessagesScalars