【Rails】ログイン認証用gemのdevise_token_auth動作確認時にNoMethodError: undefined method `downcase' for nil:NilClassエラー

1. 問題

ログイン機能の実装のため、ログイン認証用のgemであるdevise_token_authを導入した。
前提としてDocker上でフロントをVue.js、バックエンドはRails APIで実装している。

一通りdevise_token_authの設定が終わったので、Postmanから新規登録のAPIを叩いてみる

urlは、http://localhost:8000/v1/auth
paramsは、name, email, password, password_confirmationを設定した

下記のエラーが発生した

Postman

{
    "status": 500,
    "error": "Internal Server Error",
    "exception": "#<NoMethodError: undefined method `downcase' for nil:NilClass>",
    "traces": {
        "Application Trace": [],
        "Framework Trace": [
            {
                "exception_object_id": 20620,
                "id": 0,
                "trace": "rack (2.2.5) lib/rack/utils.rb:464:in `[]='"
            },
            ...
        ]
    }
}

console

backend_1   | NoMethodError (undefined method `downcase' for nil:NilClass):
backend_1   |   
backend_1   | rack (2.2.5) lib/rack/utils.rb:464:in `[]='
backend_1   | rack (2.2.5) lib/rack/utils.rb:432:in `block in initialize'
backend_1   | rack (2.2.5) lib/rack/utils.rb:432:in `each'
backend_1   | rack (2.2.5) lib/rack/utils.rb:432:in `initialize'
backend_1   | rack (2.2.5) lib/rack/utils.rb:425:in `new'
backend_1   | rack (2.2.5) lib/rack/utils.rb:425:in `[]'
backend_1   | rack (2.2.5) lib/rack/etag.rb:29:in `call'
backend_1   | rack (2.2.5) lib/rack/conditional_get.rb:40:in `call'
backend_1   | rack (2.2.5) lib/rack/head.rb:12:in `call'

2. 解決策

下記のGitHubに解決策が載っていた
https://github.com/lynndylanhurley/devise_token_auth/issues/1540

config/initializers/devise_token_auth.rbに:'authorization' => 'authorization'を追加する

config/initializers/devise_token_auth.rb

# Makes it possible to change the headers names
  config.headers_names = {:'access-token' => 'access-token',
                         :'client' => 'client',
                         :'expiry' => 'expiry',
                         :'uid' => 'uid',
                         :'token-type' => 'token-type',
                         # ↓ここを追加！！！
                         :'authorization' => 'authorization'}

修正後、再度docker-compose build、docker-compose up

conosole

docker-compose build --no-cache

docker-compose up

もう一度APIを叩いてみたら、新規登録できた！

Postman

{
    "status": "success",
    "data": {
        "id": 20,
        "provider": "email",
        "uid": "[e-mail]",
        "name": "ginger-yell",
        "email": "[e-mail]",
        "created_at": "2023-01-17T11:27:37.803Z",
        "updated_at": "2023-01-17T11:27:37.867Z"
    }
}

console

backend_1   |   User Create (2.1ms)  INSERT INTO `users` (`uid`, `encrypted_password`, `name`, `email`, `created_at`, `updated_at`) VALUES ('[e-mail]', '$1a$14$KhKsTVkilNgLofubgXGOdu32UsLF9W.BUCayj7w28oVeNNONDijy6', 'ginger-yell', '[e-mail]', '2023-01-17 11:27:37.803531', '2023-01-17 11:27:37.803531')

参考