Paginated methods: Page token field

This rule enforces that all List and Search methods have a plural name repeatable field as a first field in the response message, as mandated in AIP-158.

Details

This rule looks at any message matching List*Response or Search*Response that has next_page_token field and complains if the first field’s name is not plural.

Examples

Incorrect code for this rule:

// Incorrect
message ListBooksResponse {
  // Field name should be `books`.
  repeated Book book = 1;
  string next_page_token = 2;
}

Correct code for this rule:

// Correct.
message ListBooksResponse {
  repeated Book books = 1;
  string next_page_token = 2;
}

NOTE: If the field is a resource, the plural form of the resource type is expected.

Incorrect code for this rule (field is a resource)

import "google/api/resource.proto";

message LibraryBook {
    option (google.api.resource) = {
        type: "example.com/LibraryBook"
        pattern: "libraryBooks/{libraryBook}"
        singular: "libraryBook"
        plural: "libraryBooks"
    };
    string name = 1;
}

// Incorrect.
message ListLibraryBooksResponse {
    repeated LibraryBook books = 1;
    string next_page_token = 2;
}

Correct code for this rule (resource type):

import "google/api/resource.proto";

message LibraryBook {
    option (google.api.resource) = {
        type: "example.com/LibraryBook"
        pattern: "libraryBooks/{libraryBook}"
        singular: "libraryBook"
        plural: "libraryBooks"
    };
    string name = 1;
}

// Correct.
message ListLibraryBooksResponse {
    repeated LibraryBook library_books = 1;
    string next_page_token = 2;
}

Disabling

If you need to violate this rule, use a leading comment above the message or above the field. Remember to also include an aip.dev/not-precedent comment explaining why.

// (-- api-linter: core::0158::response-plural-first-field=disabled
//     aip.dev/not-precedent: We need to do this because reasons. --)
message ListBooksResponse {
  repeated Book book = 1;
  string next_page_token = 2;
}

If you need to violate this rule for an entire file, place the comment at the top of the file.