Re: Confusing error message for inner non-public service provider

[Peter Levart]

Hi,

Just wanted to note that the confusing javac error message is not 
specific to services and service providers.

Take the following example:

src/moda/module-info.java:

module moda {
    exports pkga;
}

src/moda/pkga/Outer.java:

package pkga;
class Outer {
    public static class Untouchable {
        public static void touch() {
            throw new AssertionError("Can't touch this!");
        }
    }
}

src/modb/module-info.java:

module modb {
    requires moda;
}

src/modb/pkgb/Intruder.java:

package pkgb;
public class Intruder {
    public static void main(String[] args) {
        pkga.Outer.Untouchable.touch();
    }
}


$ javac -d out --module-path out --module-source-path src `find src 
-name '*.java'`
src/modb/pkgb/Intruder.java:6: error: package pkga is not visible
        pkga.Outer.Untouchable.touch();
        ^
  (package pkga is declared in module moda, which does not export it to 
module modb)
1 error



Regards, Peter


On 02/09/2017 11:49 PM, Vicente Romero wrote:
Hi Alex,

Just to double check, the right javac behavior in this case should be 
to issue similar errors in both cases like:

some position here: error: ServiceImpl is not public in 
com.example.internal; cannot be accessed from outside package
some other position here: error: Outer.ServiceImpl is not public in 
com.example.internal; cannot be accessed from outside package

without mentioning in any case anything about visibility right?

Thanks,
Vicente


On 02/07/2017 02:21 PM, Alex Buckley wrote:
On 2/7/2017 1:11 AM, Gunnar Morling wrote:
     ---
     package com.example;
     public interface SomeService {
         public void foo();
     }
     ---
     package com.example.internal;
     class Outer {

         public static class ServiceImpl implements 
com.example.SomeService {
             public ServiceImpl() {}
             public void foo() {}
         }
     }
     ---
     package com.example.internal;
     class ServiceImpl implements com.example.SomeService {
         public ServiceImpl() {}
         public void foo() {}
     }
     ---
     module com.example {
         exports com.example;
         provides com.example.SomeService with 
com.example.internal.ServiceImpl;
         provides com.example.SomeService with
com.example.internal.Outer.ServiceImpl;
     }
     ---

Essentially, I'm wondering:

* Why Outer.ServiceImpl triggers the error about package visibility
while ServiceImpl doesn't (I had a look at the EDR JLS, but I couldn't
find an explanation for that, happy about any specific pointers).
* Why Outer.ServiceImpl triggers "does not have a default constructor"
(ServiceImpl does not). Maybe a hint would be nice that is caused by
Outer not having public access.

Thanks for showing the code. Since everything in the same module, 
package visibility is not relevant and javac shouldn't mention it.

I suspect that javac is getting tripped up by the fact that 
Outer.ServiceImpl is declared 'public' (as the JLS and ServiceLoader 
both demand) but it isn't widely accessible, even within the 
com.example module, due to Outer's default (package) access. I 
believe the JLS and ServiceLoader rules are correct, so it's a javac 
bug.

Alex