Fwd: [Caja] An experiment and some questions

Much of the thinking that we (especially Kevin and Dean) have done
about module systems for E may bear on Ihab's question.


---------- Forwarded message ----------
From:  <[email protected]>
Date: Feb 6, 2008 4:55 PM
Subject: [Caja] An experiment and some questions
To: Google Caja Discuss <google-caja-discuss-/[email protected]>


Hi folks,

I have been experimenting with writing the rewriter rules in
JavaScript. I will put that on hold for the moment while I take care
of the other issues but this raises a question. Is there a standard
mechanism whereby a Caja module can import another Caja module in a
capability safe manner?

In what I did, I have tried to follow E's "maker" pattern. Here is a
JavaScript module --

http://code.google.com/p/google-caja/source/browse/changes/ihab/js-rules/trunk/src/java/com/google/caja/parser/quasiliteral/defaultCajaRewriter.js

and notice that it is passed an 'importer', which is a capability to
import modules. It uses that to import another module, the source of
which is here --

http://code.google.com/p/google-caja/source/browse/changes/ihab/js-rules/trunk/src/java/com/google/caja/parser/quasiliteral/cajaRuleSupport.js

and note that this creates an *instance* of the imported module, which
has only the capabilities supplied to it by the importing module. I
used the idiom of one top-level function expression as the "return
value" of a module to achieve this. The JsImporter class, which is in
Java --

http://code.google.com/p/google-caja/source/browse/changes/ihab/js-rules/trunk/src/java/com/google/caja/parser/quasiliteral/JsImporter.java

caches the ASTs of a given module file, so it doesn't have to
re-parse, and simply re-evaluates the function every time a module is
imported.

     *    *    *    *    *

* What, if any, is or should be the equivalent functionality in Caja?
Should an importing module import another into the same ___OUTERS___,
or should the ___OUTERS___ for the imported one be "cleanroom"
isolated?

* How does that relate to other JS module systems? Should we be
working more closely with http://modulesjs.com/?

Ihab

-- 
Ihab A.B. Awad, Palo Alto, CA
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