is ClassLoader.loadClass() supposed to work on module-info classes?

[David M. Lloyd]

On 12/02/2015 08:46 AM, Remi Forax wrote:
> ----- Mail original -----
>> De: "Alan Bateman" <Alan.Bateman at oracle.com>
>> À: "Stephane Epardaud" <stef at epardaud.fr>, jigsaw-dev at openjdk.java.net
>> Envoyé: Mercredi 2 Décembre 2015 14:56:00
>> Objet: Re: is ClassLoader.loadClass() supposed to work on module-info	classes?
>>
>> On 02/12/2015 11:01, Stephane Epardaud wrote:
>>> Just tried it and got:
>>>
>>> Exception in thread "main" java.lang.ClassFormatError: Illegal class
>>> name "com.ceylon.java9.Test" in class file module-info
>>>       at java.lang.ClassLoader.defineClass1(java.base at 9.0/Native Method)
>>>       at
>>>       java.lang.ClassLoader.defineClass(java.base at 9.0/ClassLoader.java:854)
>>>       at
>>> java.security.SecureClassLoader.defineClass(java.base at 9.0/SecureClassLoader.java:152)
>>>       at
>>> java.net.URLClassLoader.defineClass(java.base at 9.0/URLClassLoader.java:462)
>>>       at
>>> java.net.URLClassLoader.access$100(java.base at 9.0/URLClassLoader.java:75)
>>>       at
>>>       java.net.URLClassLoader$1.run(java.base at 9.0/URLClassLoader.java:370)
>>>       at
>>>       java.net.URLClassLoader$1.run(java.base at 9.0/URLClassLoader.java:364)
>>>       at java.security.AccessController.doPrivileged(java.base at 9.0/Native
>>> Method)
>>>       at
>>> java.net.URLClassLoader.findClass(java.base at 9.0/URLClassLoader.java:363)
>>>       at java.lang.ClassLoader.loadClass(java.base at 9.0/ClassLoader.java:440)
>>>       at java.lang.ClassLoader.loadClass(java.base at 9.0/ClassLoader.java:373)
>>>
>>> I know it works for package-info.class files, but is it supposed to work
>>> with module-info.class files too? Or is it just not implemented yet?
>>>
>> The this_class should be <internal-name>/module-info but in any case,
>> this isn't the way to "define" a module to the run-time. Instead modules
>> are defined in layers, with Layer.create the method to create a Layer.
>
> Alan,
> there are two issues, the first one is should a module-info be accessible at runtime as a Class and the second is that the current binary format for a module-info.class break the invariant that the name of the .class is the same as the name inside of the .class because the name used for a module-info.class is the name of the module.
>
> 1) I think module-info should not be reified to a class, defineClass should reject any .class that has a module bit set in the class file format.
>     If we allow to create a Class from a module-info, a class loader may be able to load several module-info.class and it will be a real mess because module-info.class is not qualified in the jar file so the classloader will return the first seen.
> 2) In term of backward compatibility, I think i prefer that the module-info.class uses "module-info" as class name and store the name of the module inside an attribute.
>     An already existing tool that parses the bytecode format may forget to check the class version and use the module name to do something, if the name inside the module-info is "module-info", it will be easier to diagnose because the error will report a failure on "module-info" and not on a name that can also be a package name.

If it's not a class, it's pretty bizarre to call it "module-info.class". 
  At this point can we admit we're bending over backwards for principles 
that don't really add up?

-- 
- DML