Module compilation unit grammar

[Jonathan Gibbons]

More questions:

What are the restrictions on export, with respect to "clashes"?   i.e. 
what about duplicates or otherwise redundant entries?

     export p.**;
     export p.**;      // duplicate
     export p.*;       // redundant, given preceding p.**;
     export p.q;       // also redundant
     export p.p1.q;    // also redundant

-- Jon

On 04/01/2011 04:22 PM, Alex Buckley wrote:
> There are two ways to define export:
>
> 1) Export a package as a unit. No need for '.*' and it is impossible 
> to export individual types. (Allowing 'export p.q' to mean package p.q 
> but 'export p.q.r' to mean type r in package p.q is too confusing, I 
> think.)
>
> 2) Export individual types, and use '.*' to export all public types in 
> the package. Also '.**' to export all public types in subpackages.
>
> I prefer (2) because:
>
> - While it's appealing to think of a package as a unit, the reality is 
> that a package is nothing more than a qualifier on a type name. A 
> module system doesn't make a package visible per se; it makes certain 
> public types in a package visible.
>
> - 'import' already provides a type-centric view of the world. Even if 
> you write 'import foo.*', you are aware of individual types within 
> package foo. I think we should stick with it for 'export'. Good 
> practice may end up being to export individual type names, as it is 
> with import.
>
> - It allows the .** "all subpackages" export, which (1) would 
> enumerate individually.
>
> (2) adds the burden of classifying names as package names or type 
> names; see below. (2) also requires more of the module system, though 
> in no way does it cause split packages at runtime any more than (1).
>
> I propose:
> - 'export p' is invalid because p is not a qualified name.
> - 'export p.q' means export the single type p.q.
> - 'export p.*' means export all public types in package p.
> - 'export p.**' means export all public types in package p and its 
> subpackages, and their subpackages, etc.
> - 'export p.q.*' means export either all public types in package p.q 
> or all public member types in type q in package p - depending on p.q's 
> classification given the module's membership.
>
> Alex
>
> On 4/1/2011 3:33 PM, Mandy Chung wrote:
>>  Adding to Jon's question:
>>
>>     export p.*;
>>
>> Does '*' match '.' in the package name?  If not, it'd be useful to 
>> support '**' like syntax e.g. 'export java.**;'  exports all package 
>> names with 'java.' prefix.
>>
>> Mandy
>>
>> On 4/1/11 3:05 PM, Jonathan Gibbons wrote:
>>> Is the asterisk form of export constrained to packages and/or is it 
>>> required for packages?
>>>
>>> For example, which of the following are valid
>>>
>>>     export p;
>>>     export p.*;
>>>     export p.Clazz;
>>>     export p.Clazz.*;
>>>
>>> -- Jon
>>>
>>>
>>> On 03/11/2011 03:51 PM, Alex Buckley wrote:
>>>> Here is the current grammar used by javac to parse a module 
>>>> compilation unit ("module-info.java").
>>>>
>>>>
>>>> * Example
>>>>
>>>> module a.b @ 1.0 {
>>>>   require c.d @ [2.0,3.0);
>>>>   export  e.f.*;
>>>>   provide g.h @ 4.0;
>>>>   permit  i.j;
>>>>   class   k.l;
>>>> }
>>>>
>>>> - A compilation unit may contain a module declaration.
>>>>
>>>> - A module declaration may not be annotated.
>>>>
>>>> - A module name is a qualified identifier, in the spirit of a 
>>>> package-or-type name and a type name (JLS3 6.5).
>>>>
>>>> - A module version is like a qualified identifier, except that the 
>>>> characters of the identifier may be any Java letter or digit (to 
>>>> allow a first numeric character) and the qualifier may be .+-:~ (as 
>>>> per 
>>>> http://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-Version, 
>>>> referred to by org/openjdk/jigsaw/JigsawVersion.java).
>>>>
>>>> - require takes a qualified identifier indicating a module name, 
>>>> optionally followed by '@' and a version query. A version query is 
>>>> an exact version or an interval.
>>>>
>>>> - require supports 'local' and 'optional' flags. There is no 
>>>> 'public' flag because re-export is handled by the export statement.
>>>>
>>>> - export takes a qualified identifier indicating a package or type 
>>>> name, possibly ending in '. *'.
>>>>
>>>> - permit takes a qualified identifier indicating a module name.
>>>>
>>>> - class takes a qualified identifier indicating a type name.
>>>>
>>>> - require/local/optional/export/provide/permit are restricted 
>>>> keywords.
>>>>
>>>>
>>>> * Grammar
>>>>
>>>> [x] denotes zero or one occurrences of x.
>>>> {x} denotes zero or more occurrences of x.
>>>> (x|y) means one of either x or y.
>>>>
>>>>
>>>> CompilationUnit:
>>>>   [PackageDeclaration] [ImportDeclaration] [TypeDeclaration]
>>>>   [ModuleDeclaration]
>>>>
>>>> ModuleDeclaration:
>>>>   'module' ModuleName ['@' Version] '{' {ModuleStatement} '}'
>>>>
>>>> ModuleName:
>>>>   Identifier
>>>>   ModuleName '.' Identifier
>>>>
>>>> ModuleStatement:
>>>>   ModuleRequire
>>>>   ModuleProvide
>>>>   ModuleExport
>>>>   ModulePermit
>>>>   ModuleClass
>>>>
>>>> ModuleRequire:
>>>>   'require' [ModuleRequireModifier] ModuleName ['@' VersionQuery] ';'
>>>>
>>>> ModuleRequireModifier:
>>>>   'local'
>>>>   'optional'
>>>>
>>>> ModuleExport:
>>>>   'export' PackageOrTypeName ['.' '*'] ';'
>>>>
>>>> ModuleProvide:
>>>>   'provide' ModuleName ['@' Version] ';'
>>>>
>>>> ModulePermit:
>>>>   'permit' ModuleName ';'
>>>>
>>>> ModuleClass:
>>>>   'class' TypeName ';'
>>>>
>>>> VersionQuery:
>>>>   Version
>>>>   ('['|'(') Version ',' Version (')'|']')
>>>>
>>>> Version:
>>>>   ModuleIdentifier {VersionTokenizer ModuleIdentifier}
>>>>
>>>> ModuleIdentifier:
>>>>   JavaLetterOrDigit
>>>>   ModuleIdentifier JavaLetterOrDigit
>>>>
>>>> VersionTokenizer:
>>>>   . or + or - or : or ~
>>>>
>>>
>>