Applet and Servlet Compile Options

[Per Bothner]

On 03/02/2013 07:21 AM, Matthieu Vachon wrote:
> Hi Per,
>
> I started to work on the `applet:` and `servlet:` module compile
> options. It is a bit harder than what I was thinking.
>
> The problem comes from the moment at which `module-compile-options`
> are parsed. Indeed, just before parsing, `Compilation` will push the
> module being compiled with `pushNewModule`. In this code, we check if
> we are generating an applet or a servlet and then, we set the flag
> `SUPERTYPE_SPECIFIED` on the module.

Hm.  There are indeed a a couple of different solutions, none
strikingly appealing.

The most obvious is to replace the checks for SUPERTYPE_SPECIFIED
to also check for applet and servlet.  Probably by using a method
like isSupertypeSpecified.

Cleaner would be to defer the check in pushNewModule to when we
actually need it.  The simplest is just move it from pushNewModule
to Translator#finishModule.  There is a good chance that would
work, but it needs some testing.

More generally:

Kawa Scheme has an implicit (i.e. under-documented) concept of the
module header.  Certain forms, including module-extends and module-name,
should only be specified in the module header.  How far the
module header extends is vague, but it certainly does not extend
beyond the first require or import.  Consider module-name - this
needs to be set before require/import, in case of a group of
modules that recursively require each (which Kawa supports).

Perhaps we need to formalize this.  Maybe Translator needs a
new method named commitModule or finishModuleHeader.  This
would set SUPERTYPE_SPECIFIED if applet or servet is requested.
It would also set a flag that the module header is done, perhaps
ModuleExp#HEADER_FINISHED.  Then for example module-name would
report an error if HEADER_FINISHED is set.  Likewise some
of the module-compile-option would only be allowed in the header.

Right now, if you compile a module like:

(require whatever)
(module-name bar)

You get a rather uninformative error message:

/tmp/foo.scm:2:1: duplicate module-name: old name: foo

If we have a HEADER_FINISHED flag we could do better - e.g.:

/tmp/foo.scm:2:1: module-name must be set in module header
-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/