ability.can requires third parameters to be string and subject() doesn't work about casl

[stalniy]

It seems it's not a CASL issue. I've just finished example of CASL + Fastify + Prisma and all was good. Please check it here -> https://github.com/stalniy/casl-examples/tree/master/packages/fastify-prisma-blog

[hathinhks]

@stalniy But the error is from calling method on the casl ability object, so how is that not a CASL issue?
Please help me figure out the root cause of this problem. I don't understand why it requires the third parameter to be a string.
My application is a nestjs project by the way.

[stalniy]

const aNumber: string = 1; // ts error

Who's that error above? :)

You are asking me to look in your code, understand details and help to solve the issue but I do not provide support services for free. I'm pretty sure this is not casl issue because:

1. There are tests that validate all different cases
2. I've just finished example which works and has no unexpected behavior. You can check it and understand how your code is different from the example and fix it yourelf

[hathinhks]

@stalniy it'd be easier if the error comes from my code, but it's from the ability.can() method from casl package. As I understand the parameters that ability.can() accepts are defined in within these lines of code, am I correct?

type AppAbility = PureAbility<
  [
    string,
    (
      | Subjects<{
        User: User
      }>
      | 'all' 
    ),
  ],
  PrismaQuery
>

const { can, cannot, build } = new AbilityBuilder<AppAbility>(createPrismaAbility)

The first parameters to PureAbility is the type of the action (in this case string) and the accepted subject, and the second is the condition object, which in this case is PrismaQuery. There's not a place that defining a third 'string' type parameter.
My code looks almost identical to the documentation, so that's why I don't understand the reason behind the error.

[coolbho3k]

@hathinhks I just figured this out, the error message is rather opaque. The Prisma example is not TypeScript in the docs so it doesn't work as-is. The solution is very simple.

The object passed into subject needs to be of type User. You need the as User as follows:

ability.can(Action.Read, subject('User', { role: UserRole.admin } as User));

[coolbho3k]

Actually scratch what I just said You may be running into this: #778