import-no-cycle (Protobuf linter rule)

import-no-cycle

Since 0.9.0

This rule checks whether Protobuf files import each other in a cycle.

Rule Details

protoc rejects files that import themselves through a chain of imports, so such files cannot be compiled at all.

For every import of the linted file, the import-no-cycle rule follows the imports of the imported file, and of the files it imports, looking for a path back to the linted file. If there is one, it reports:

Import '<import>' creates an import cycle: <file name> -> <import> -> ... -> <import>

A file that imports itself is reported with Import '<import>' creates an import cycle: the file imports itself.

The cycle starts with the name of the linted file, followed by the imports that lead back to it, as they are written in the import statements. Every file of the cycle that is linted reports its own import.

Imports that cannot be found are ignored (see import-resolved). Files linted without a path are not checked.

Configuration

This rule has no options.

Examples

Good. acme/pets/v1/pet.proto imports acme/pets/v1/owner.proto, which imports nothing from the package.

syntax = "proto3";

package acme.pets.v1;

import "acme/pets/v1/owner.proto";

message Pet {
  string name = 1;
  Owner owner = 2;
}

Bad. The same acme/pets/v1/pet.proto, while acme/pets/v1/owner.proto imports it back:

syntax = "proto3";

package acme.pets.v1;

import "acme/pets/v1/pet.proto";

message Owner {
  string name = 1;
  repeated Pet pets = 2;
}

The linter reports, in pet.proto:

Import 'acme/pets/v1/owner.proto' creates an import cycle: pet.proto -> acme/pets/v1/owner.proto -> acme/pets/v1/pet.proto

and in owner.proto:

Import 'acme/pets/v1/pet.proto' creates an import cycle: owner.proto -> acme/pets/v1/pet.proto -> acme/pets/v1/owner.proto

When Not to Use It

We recommend to always enable this rule.

Compatibility