types: correct this for validate.validator schematype option

[vkarpov15]

Fix #14696

Summary

Ensure this has the correct type in validate.validator below.

    isActive: {
      type: Boolean,
      default: false,
      validate: {
        validator(v: any) {
          expectAssignable<User>(this);
          return !v || this.name === 'super admin';
        }
      }
    }

I made 2 changes to support this:

1. passing EnforcedDocType down to ValidateFn via ValidateOpts and SchemaValidator
2. Removing LegacyAsyncValidateFn. For some reason, LegacyAsyncValidateFn breaks these tests, and I have no idea why. It has something to do with the done function. Either way, LegacyAsyncValidateFn is no longer necessary because we removed support for validators that receive a callback in Mongoose 6, so I think it is safe to remove.

Examples

[pharapeti]

For context: I'm upgrading from Mongoose v8.2.2 to v8.6.3

When performing a document create/update, this is the document (mongoose.Document).
When performing a MyModel.findOneAndUpdate query with options { runValidators: true }, this becomes is the query (mongoose.Query).

However, I believe due to these type changes make in this PR, Typescript seems to believe that this is always the document type - even in the case when it is a query.

Do you have any idea on how I can type the validator function so that Typescript knows that this is either a document OR a query type? @vkarpov15 @hasezoey

---

EDIT: After some experimentation, I managed to get the following somewhat working solution by specifying the type of this in the validator function.

type ValidatorThis = DocumentValidatorThis | QueryValidatorThis;
type DocumentValidatorThis = mongoose.Document & PassPersisted;
type QueryValidatorThis = mongoose.Query<PassRecord, PassPersisted>; // This is probably incorrect

endTime: {
  type: Date,
  required: true,
  validate: {
    validator: async function(this: ValidatorThis, endTime ): Promise<boolean> {
      if ('op' in this) {
        // Query validator
        const queryThis = this as QueryValidatorThis;
        let startTime: Date = this.get( 'pass.startTime' );

        ... can access query via `this`

        return endTime.getTime() > startTime.getTime();
      } else {
        // Document validator
        const documentThis = this as DocumentValidatorThis;
        return endTime.getTime() > documentThis.startTime.getTime();
      }
    },
    message: ( endTime ): string => `End time (${ endTime.value.toISOString() }) is before its start time`
  }
},

[vkarpov15]

@pharapeti you're right that the workaround is to explicitly set the type of this in the validator function. We don't currently have | Query in the fix in this PR, and adding it would be a breaking change. We're going to put in a PR to fix this issue and some related issues, but you'll likely have to use the workaround with explicit this typing for the near future.

[pharapeti]

@vkarpov15 Thanks for confirming that, will implement the workaround for now 👍

Cheers for the speedy reply 🙏