Hermetic Evaluation, Modules Strawman

Kris Kowal kris.kowal at cixar.com
Wed Sep 30 04:33:55 PDT 2009

I've begun my work on a second draft [1] of the module proposal that
Ihab and I put forth at the January meeting.  Just to get started, I
wanted to emphasize that "all we need is hermetic evaluation", and
re-propose the interface for hermetic eval in light of experience with
the CommonJS [2] and Narwhal [3] implementations of the
SecurableModules [4] proposal Ihab and I made to that group a week
later.  We've made a lot of great progress in the last 9 months in
vetting the module system idea.

This new draft proposes that the primitive hermetic evaluator be more
like the Function constructor and permits early exceptions for
non-primordial, non-injected free variables.  The new proposal is
safer since it emphasizes that the module text must be a program
construct, makes explicit what names are being injected into the
program's scope, and explicates that, unlike "with" blocks, specific
names are injected into a function block scope instead of placing a
stock Object in the scope chain.

It's my intention to copy and edit sections of the original proposal
into the wiki, making minor revisions to match up with CommonJS
SecurableModules, the Module meta-object amendment [5], explicate
synchronous and asynchronous variations of importing modules, and to
specify the API's of module loaders and module sandboxes.  Ihab is
spearheading an effort on CommonJS to formalize "packages" of modules,
their layout, their metadata, how to verify their signatures, and how
to import modules from packages, which I hope to integrate in a future
draft.  We remain in discord about whether to conflate the name spaces
of injected capabilities and modules, but we had a good discussion
recently that might help us arrive at a compromise.

This all being said, between Object.freeze and hermetic evaluation, we
can do a lot in libraries without native language support so it's
worth kicking off a discussion around that feature early.

Kris Kowal

[1] http://wiki.ecmascript.org/doku.php?id=strawman:modules
[2] http://wiki.commonjs.org/wiki/CommonJS
[3] http://narwhaljs.org/
[4] http://wiki.commonjs.org/wiki/Modules/SecurableModules
[5] http://wiki.commonjs.org/wiki/Modules/Meta

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