# enum-no-allow-alias

Source: https://apigenie.pl/docs/linter/protobuf/rules/enum-no-allow-alias

This rule checks whether any enum sets the `allow_alias` option.

## Rule Details

With `option allow_alias = true;`, several values of an enum can share a number. Only one of the
names survives serialization, though: the JSON and text formats always write the first name of
the number, so a client that sends one name may read back another. Aliases also make renaming
values harder than it looks, since both names have to be kept in sync with every consumer.

The `enum-no-allow-alias` rule reports `Enum '<enum>' should not allow aliases` at the
`allow_alias` option of every enum that sets it to `true`.

## Configuration

This rule has no options.

## Examples

**Good**.

```proto
syntax = "proto3";

package acme.pets.v1;

enum PetKind {
  PET_KIND_UNSPECIFIED = 0;
  PET_KIND_DOG = 1;
  PET_KIND_CAT = 2;
}
```

**Bad**. The linter reports `Enum 'PetKind' should not allow aliases`.

```proto
syntax = "proto3";

package acme.pets.v1;

enum PetKind {
  option allow_alias = true;
  PET_KIND_UNSPECIFIED = 0;
  PET_KIND_DOG = 1;
  PET_KIND_HOUND = 1;
  PET_KIND_CAT = 2;
}
```

## When Not to Use It

You may disable this rule while renaming enum values: an alias lets the old and the new name
coexist until all clients have moved to the new one. To allow a single enum, add an
`// apigenie-lint-disable enum-no-allow-alias` comment to the enum.

## Compatibility

This rule is compatible with proto3 files. proto2 and editions files are rejected by the reader
and are not linted.