Should standard library service types be distinct

[shafreenAnfar]

At the moment all the standard library service type definitions looks as follows,

public type SomeService service object {};

which results in the below usages,

With service declaration

listener Listener l = new(); 
service /foo on l {
   // some resources
}

Without service declaration

public service class MyService {
   // some resources
}

public function main() returns error? {
    Listener l = check new;
    MyService myService = new;
    check l.attach(myService, "/foo");  
}

To ensure the structure of the service (MyService) complier plugin is engaged during the compile time.

However, if we make the service type definition distinct, the usage would be as follows.

public type SomeService distinct service object {};

With service declaration

listener Listener l = new(); 
service /foo on l {
   // some resource
}

No change in the usage.

Without service declaration

public service class MyService {
    *SomeService;
   // some resources
}

public function main() returns error? {
    Listener l = check new;
    MyService myService = new;
    check l.attach(myService, "/foo");  
}

To ensure the structure of the service (MyService) complier plugin is engaged during the compile time.

However, in this case,

• Code becomes a bit more readable as we need to explicitly mention that MyService is a subtype of SomeService.
• It allows us to distinguish one service from another during runtime using type-ids.
• It becomes easier to write the complier plugin logic as we can easily distinguish MyService from the rest of the services in a given program.

Therefore, even though this is not a situation where we interop with a nominal type systems like Java or GraphQL, would it be a good idea to mark all the standard library services with distinct for SwanLake ?

[shafreenAnfar]

@jclark we would like to get your suggestion on this.

[jclark]

If your service object types are currently defined as empty (without any members), then I think adding distinct is a good idea.

[shafreenAnfar]

Actually, there is a slight mistake in the original description. When a service type is marked as distinct, it actually impacts the service declaration. You have to explicitly mention the service type as below. Therefore, we decided not to make services distinct.

service MyService / on ll {
}

Without distinct

service / on ll {
}

[jclark]

@shafreenAnfar I don't think that's a spec requirement (if it is, it shouldn't be).

[rdhananjaya]

This is a spec deviation in inferring the static type of the service declaration.
Moving the issue to the ballerina-lang repo.

[shafreenAnfar]

As per the discussion we have update the standard library services.