Confusing error message for inner non-public service provider

[Peter Levart]

Hi Jon,

I understand that service providers have a different set of rules (they 
are usually not universally accessible classes) and therefore the 
requirement for them to have public access modifier is merely a choice 
JLS made to enforce a certain degree of strictness. Classes with default 
(package-private) modifier could easily be allowed too, but I guess some 
strictness is welcome. I just wanted to share what I observed: that the 
javac error message is similar also when trying to access a public 
nested class in a package-private enclosing class in an exported 
package, from a different module, which has nothing to do with service 
providers.

Regards, Peter

On 02/13/2017 08:10 PM, Jonathan Gibbons wrote:
> Peter,
>
> The circumstances of the analysis of service providers are very 
> different to the normal JLS rules regarding visibility and 
> accessibility of named items.
>
> I know that we have some cleanup to do, for javac to "catch up" with 
> the latest updates to JLS, especially with regards to the difference 
> between "visibility" and "accessibility".   Is that the issue you 
> concerned about, or is there something else about this message you 
> find confusing.
>
> -- Jon
>
> On 02/13/2017 09:08 AM, Peter Levart wrote:
>> 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
>>>
>>
>