Better Auth Plugin Typescript Errors in VueJS

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Summary

The issue at hand is a TypeScript error that occurs when trying to access the multiSession property of the authClient instance in a VueJS application. The error is caused by the fact that the createAuthClient function from the Better Auth library does not include the type definitions for the plugins used.

Root Cause

The root cause of this issue is that the TypeScript compiler is unable to infer the types of the plugins used in the createAuthClient function. This is because the plugins are not properly typed, leading to a type error when trying to access the multiSession property.

Why This Happens in Real Systems

This issue can occur in real systems when using third-party libraries that do not provide proper type definitions or when using plugins that are not properly typed. Some common reasons for this include:

  • Insufficient type definitions: The library or plugin does not provide sufficient type definitions, leading to type errors.
  • Incorrect plugin usage: The plugin is not used correctly, leading to type errors.
  • TypeScript configuration: The TypeScript configuration is not set up correctly, leading to type errors.

Real-World Impact

The real-world impact of this issue is that it can prevent the application from being built, leading to delays and frustration. Some potential impacts include:

  • Build errors: The application cannot be built due to type errors.
  • Runtime errors: The application may throw errors at runtime due to incorrect typing.
  • Maintenance difficulties: The application may be difficult to maintain due to type errors and inconsistencies.

Example or Code

import { createAuthClient } from 'better-auth/vue';
import { multiSessionClient } from 'better-auth/client/plugins';
import { organizationClient } from 'better-auth/client/plugins';

export const authClient = createAuthClient({
  baseURL: 'http://localhost:8080',
  plugins: [multiSessionClient(), organizationClient()],
});

async function loadDeviceSessions() {
  try {
    const { data, error: sessionError } = await (authClient as any).multiSession.listDeviceSessions();
    if (sessionError) {
      throw sessionError;
    }
    sessions.value = data || [];
  } catch (err) {
    error.value = err;
  } finally {
    loading.value = false;
  }
}

How Senior Engineers Fix It

Senior engineers can fix this issue by:

  • Checking the library documentation: Verify that the library provides proper type definitions and that the plugins are used correctly.
  • Using type assertions: Use type assertions to tell TypeScript that the authClient instance has the multiSession property.
  • Creating custom type definitions: Create custom type definitions for the plugins used in the application.
  • Updating the library: Update the library to include proper type definitions for the plugins.

Why Juniors Miss It

Junior engineers may miss this issue because:

  • Lack of experience: Junior engineers may not have experience with TypeScript or the specific library being used.
  • Insufficient knowledge of type systems: Junior engineers may not have a deep understanding of type systems and how to use them effectively.
  • Rushing to implement features: Junior engineers may be focused on implementing features quickly and may not take the time to properly investigate type errors.