Issue with CredentialsProvider in NextAuth.js when Changing Credential Fields

[Prashant-S29]

Provider type

Credentials

Environment

 System:
    OS: Windows 11 10.0.22631
    CPU: (12) x64 AMD Ryzen 5 5625U with Radeon Graphics
    Memory: 2.27 GB / 15.34 GB
  Binaries:
    Node: 22.7.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.8.3 - C:\Program Files\nodejs\npm.CMD
    bun: 1.1.27 - ~\AppData\Roaming\npm\bun.CMD
  Browsers:
    Edge: Chromium (127.0.2651.74)
    Internet Explorer: 11.0.22621.3527
  npmPackages:
    @auth/prisma-adapter: ^2.7.2 => 2.7.4
    next: ^15.0.1 => 15.0.3
    next-auth: 5.0.0-beta.25 => 5.0.0-beta.25
    react: ^18.3.1 => 18.3.1

Reproduction URL

https://github.com/Prashant-S29/ici-fest-skit.git

Describe the issue

Issue with CredentialsProvider in NextAuth.js when Changing Credential Fields

Description

I am experiencing an issue with CredentialsProvider in NextAuth.js. The error occurs when I modify the default credentials object to include additional fields.

Here is the situation:

• When using the default credentials object, everything works fine.
• When I change the credentials object to include additional fields, I encounter an error.

I have strict: true set in my tsconfig.json file.

Working Code

This configuration works without any issues:

CredentialsProvider({
  type: "credentials",
  credentials: {
    email: { label: "Email", type: "email" },
    password: { label: "Password", type: "password" },
  },
});

Non-Working Code

When I change the credentials object as shown below, I get an error:

CredentialsProvider({
  type: "credentials",
  credentials: {
    adminId: { label: "Admin ID", type: "text" },
    password: { label: "Password", type: "password" },
    eventId: { label: "Event ID", type: "text" },
  },
});

TS Error message

When I change the credentials object as shown above, I get this TS error:

Type '(credentials: Credential | null) => Promise<{ id: string; role: string; eventId?: undefined; } | { id: string; eventId: string; role?: undefined; } | null>' is not assignable to type '(credentials: Partial<Record<"eventId" | "adminId" | "password", unknown>>, request: Request) => Awaitable<User | null>'.
  Types of parameters 'credentials' and 'credentials' are incompatible.
    Type 'Partial<Record<"eventId" | "adminId" | "password", unknown>>' is not assignable to type 'Credential'.
      Types of property 'adminId' are incompatible.
        Type 'unknown' is not assignable to type 'string | undefined'.ts(2322)
credentials.d.ts(53, 5): The expected type comes from property 'authorize' which is declared here on type 'Partial<CredentialsConfig<{ adminId: { label: string; type: string; }; password: { label: string; type: string; }; eventId: { label: string; type: string; }; }>>'

Additional Context

• I have strict type checking enabled (strict: true) in my tsconfig.json file.
• The error message does not provide a clear solution.
• It seems like there might be a type mismatch or an issue with how the new fields are being validated.

How to reproduce

Steps to Reproduce

Prerequisites

• Ensure you have Node.js and npm installed
• Have Git configured on your system

Steps

1. Clone the Repository and Set Up the Project
   Clone the repository and install the required dependencies by following the version specifications mentioned in the project documentation.

   git clone <repo-url>
   cd <repo-folder>
   # Install dependencies
   npm install

2. Navigate to the Configuration File
   Locate the config.ts file in the following project structure:

   root/
   └── src/
       └── server/
           └── auth/
               └── config.ts
   

3. Observe the Error
   Open the config.ts file and review the error message that appears. This might be related to incorrect configurations or other issues in the file.

Expected behavior

Expected Behavior

I expect to be able to modify the credentials object to include custom fields without encountering any errors.

Actual Behavior

An error occurs when I add custom fields to the credentials object.

Environment

• NextAuth.js Version: [Specify version]
• TypeScript Version: [Specify version]
• Node.js Version: [Specify version]
• Operating System: [Specify OS]

Question

• Is there a specific TypeScript type I need to define to allow custom fields in the credentials object?
• Are there any additional configurations required in NextAuth.js to support custom credential fields?

Any help or suggestions would be greatly appreciated!

[halvaradop]

This is not a real issue. Let me explain more clearly what is happening:

1. Defining Fields in the Credentials Provider

The Credentials provider allows you to define the properties of the data that will be received from the signIn("credentials", ...data) function when using a supported framework like Next.js, Qwik, and others. By specifying the expected fields, you get autocomplete suggestions for the fields available in the authorize function provided by the Credentials provider.

Credentials({
    credentials: {
        adminId: { label: "Admin ID", type: "text" },
        password: { label: "Password", type: "password" },
        eventId: { label: "Event ID", type: "text" },
    },
    async authorize(credentials, req) {
        // No error is generated because 'adminId' is defined in the credentials object
        credentials.adminId;
        // Property 'email' does not exist on type 'Partial<Record<"adminId" | "password" | "eventId", unknown>>'
        credentials.email;
    },
});

With this approach, you avoid having to manually cast types like this:

async authorize(credentials, req) {
    const { adminId, password, eventId } = credentials as { adminId: string; password: string; eventId: string };
}

2. Missing authorize Function

If you attempt to log in using signIn("credentials", ...data) without implementing the authorize function, you’ll receive a credentialssignin error. This happens because the session creation fails, as the authorize function is not defined, which is expected behavior.

3. Error in the authorize Function

If you implement the authorize function but continue encountering an error, this might be because the authorize function must return properties expected by the User interface. The adminId, password, and eventId fields are not part of the User interface.

If you'd like to learn more, you can read the official documentation: Auth.js TypeScript Guide.

Relevant User Interface Definition

export interface User {
  id?: string;
  name?: string | null;
  email?: string | null;
  image?: string | null;
}