Here's one other post about this from Allen: https://github.com/tc39/ecma262/issues/749#issuecomment-265637923
On Wed, Oct 24, 2018 at 10:42 AM T.J. Crowder < [email protected]> wrote: > I'm curious if I've inferred the rationale for something correctly. > > The module namespace object properties for exports have `writable: true` > in their property descriptors, but of course, they aren't writable (the > module namespace object has its own [[Set]] implementation that returns > false). I wondered why they weren't `writable: false`, so I went looking. > > I found discussion in the March 24 2015 meeting notes about whether to > even have `getOwnPropertyDescriptor` work. The consensus was yes, it should > work (mixins!), and that it should report a basic data property that isn't > configurable -- but is writable. Yahuda Katz points out that: > > > it is writable, but it's not writable by you > > though that's not always true (it may be declared `const`; that > information isn't leaked from the module, though). > > In the May 25 2017 notes I found a comment from Mark S. Miller in relation > to `writable: true`: > > > Non-writeable provides guarantee. Writable provides no guarantee. > > And this exchange between Yahuda Katz, Allen Wirfs-Brock, and Adam Klein: > > > YK: There is a a new property that we define as writable that is not > writable. > > > > AWB: Not new. > > > > AK: Since... Proxys! > > There was some discussion of considering some flag basically saying what > YK said, e.g., it's writable, but not by you :-) -- but that was more a > brief digression that didn't go anywhere. > > So, then, what I infer is: They're marked writable because: > > 1. They may be writable by the exporting module, so code can't assume the > value won't change; `writable: false` would make that assumption valid > 2. Whether or not they're writable by the exporting module isn't > information that should leak out of it > 3. Non-writable `writable: true` data properties were already a thing > (Proxies) > > So the most sensible thing was `writable: true` rather than `writable: > false`. > > How'd I do? :-) > > -- T.J. Crowder > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
_______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
