[External] : Re: JEP 476: Clarification on Package Export Behavior in Java Modules

[Alex Buckley]

You're not importing the my.nice.project.pkg.{a,b} packages at all, so 
the names SomeRecord and SomeInterface are unknown.

`import module ...` will only import the packages exported from the module.

If the my.nice.project module doesn't export anything, then `import 
module my.nice.project` is not a substitute for on-demand/single-type 
imports.

If the my.nice.project module exports the two packages to itself, then 
`import module my.nice.project` from within the module should work as a 
substitute for on-demand/single-type imports.

Alex

On 9/13/2024 12:28 PM, Thiago Henrique Hupner wrote:
> Source structure:
> 
> src
>      |   module-info.java
>      \---my
>          \---nice
>              \---project
>                  |   Main.java
>                  \---pkg
>                      +---a
>                      |       SomeInterface.java
>                      \---b
>                              SomeRecord.java
> 
> I've tried both commands with and without the module import and they 
> both fail:
> 
> java --enable-preview src/my/nice/project/Main.java
> 
> 
> javac --release 23 --enable-preview -d ./mod ./src/module-info.java ./ 
> src/my/nice/project/Main.java ./src/my/nice/project/pkg/a/ 
> SomeInterface.java ./src/my/nice/project/pkg/b/SomeRecord.java
> 
> However, exporting a package to the my.nice.project module and including 
> the module import both commands work.
> 
> 
> .\src\my\nice\project\pkg\a\SomeInterface.java:7: error: cannot find symbol
>      public SomeRecord someMethod();
>             ^
>    symbol:   class SomeRecord
>    location: interface SomeInterface
> .\src\my\nice\project\Main.java:7: error: cannot find symbol
>          SomeInterface someInterface = new SomeInterface() {
>          ^
>    symbol:   class SomeInterface
>    location: class Main
> .\src\my\nice\project\Main.java:7: error: cannot find symbol
>          SomeInterface someInterface = new SomeInterface() {
>                                            ^
>    symbol:   class SomeInterface
>    location: class Main
> .\src\my\nice\project\Main.java:9: error: cannot find symbol
>              public SomeRecord someMethod() {
>                     ^
>    symbol: class SomeRecord
> .\src\my\nice\project\Main.java:8: error: method does not override or 
> implement a method from a supertype
>              @Override
>              ^
> .\src\my\nice\project\Main.java:10: error: cannot find symbol
>                  return new SomeRecord();
>                             ^
>    symbol: class SomeRecord
> 6 errors
> 
> 
> Best regards,
> 
> Thiago
> 
> Em sex., 13 de set. de 2024 às 15:53, Alex Buckley 
> <alex.buckley at oracle.com <mailto:alex.buckley at oracle.com>> escreveu:
> 
>     If removing the imports doesn't fix the errors, then I'm suspicious of
>     your compiler setup.
> 
>     Please describe on this mailing list the commands you're using and the
>     actual javac errors that you see.
> 
>     Alex
> 
>     On 9/13/2024 9:41 AM, Thiago Henrique Hupner wrote:
>      > Removing the imports still doesn't fix the errors.
>      >
>      > I've create a Github repo with the reproducer: https://
>     github.com/ <https://urldefense.com/v3/__https://github.com/__;!!
>     ACWV5N9M2RV99hQ!I4FDC_5bZkrDbMH-KZS-5Acu-
>     JIodeUAiW82iZl2Ozjm04tx6e3VXy1ug49pGDiAOGAKVnPCOoj1tF9KrA$>
>      > Thihup/module-import-bug
>      >
>      > Best regards,
>      >
>      > Thiago
>      >
>      >
>      > Em sex., 13 de set. de 2024 às 12:41, Alex Buckley
>      > <alex.buckley at oracle.com <mailto:alex.buckley at oracle.com>
>     <mailto:alex.buckley at oracle.com <mailto:alex.buckley at oracle.com>>>
>     escreveu:
>      >
>      >     I assume that the package my.nice.project is colocated with
>     the other
>      >     two packages -- my.nice.project.pkg.{a,b} -- in the module
>      >     my.nice.project.
>      >
>      >     If so, then all three packages should be able to access each
>     others'
>      >     public types (SomeInterface, SomeRecord) without error.
>      >
>      >     The fact that you're getting an error looks like a javac bug.
>      >
>      >     You don't need to `import module my.nice.project` in the source
>      >     files of
>      >     that module. Try removing those imports and see if
>     my.nice.project.Main
>      >     compiles (it should).
>      >
>      >     Alex
>      >
>      >     On 9/13/2024 5:00 AM, Thiago Henrique Hupner wrote:
>      >      > Dear Amber Team,
>      >      >
>      >      > I hope you're doing well. I’ve encountered a behavior
>     related to JEP
>      >      > 476: Module Import Declarations and wanted to ask for
>     clarification.
>      >      >
>      >      > I’m working with a module setup where two packages are defined
>      >     but not
>      >      > initially exported:
>      >      >
>      >      > |module my.nice.project { //exports my.nice.project.pkg.a to
>      >      > my.nice.project; //exports my.nice.project.pkg.b to
>      >     my.nice.project; } |
>      >      >
>      >      > Here’s a simplified version of the code structure:
>      >      >
>      >      >
>      >      > |package my.nice.project;
>      >      > |
>      >      > |
>      >      > |import module my.nice.project;|
>      >      >
>      >      > |
>      >      > |public class Main { public static void main(String[] args)
>      >      > { SomeInterface someInterface = new SomeInterface()
>     { @Override
>      >     public
>      >      > SomeRecord someMethod() { return new SomeRecord(); } }; } }|
>      >      >
>      >      > |
>      >      > |
>      >      > |package my.nice.project.pkg.a; import module
>     my.nice.project;|
>      >      > |
>      >      > |
>      >      > |public interface SomeInterface { public SomeRecord
>     someMethod(); }|
>      >      >
>      >      > |package my.nice.project.pkg.b; public record SomeRecord()
>     {} |
>      >      >
>      >      > When attempting to compile this code with the exports
>     commented
>      >     out, I
>      >      > received several "cannot find symbol" errors. However, after
>      >      > uncommenting the exports:
>      >      >
>      >      >
>      >      > |exports my.nice.project.pkg.a to my.nice.project; exports
>      >      > my.nice.project.pkg.b to my.nice.project; |
>      >      >
>      >      > The code compiled and ran as expected.
>      >      >
>      >      > Given this behavior, I wanted to confirm if this
>     restriction on
>      >     package
>      >      > visibility within a module is the intended design under
>     the Amber
>      >      > project and the module system, or if there’s another
>     approach or
>      >     best
>      >      > practice I might be overlooking in terms of package exports.
>      >      >
>      >      > Thank you for your time and insight.
>      >      >
>      >      > Best regards,
>      >      >
>      >      > Thiago
>      >      >
>      >
>