> I think we probably have an interesting question for Dave and Sam about how
> to support version evolution of modules. Is there a module equivalent of
> monkey patching. What if we have an implementation that exposes a "V1" module
> (particularly a built-in module) and code that depends upon upon a V2 of that
> same module that has an expanded export list. Is there anyway for that code
> to patch the module to add the extra exported APIs it would like to use?
ES6 modules are not extensible, for a number of reasons including compile-time
variable checking. But of course API evolution is critical, and it works; it
just works differently. Monkey-patching says "let the polyfill add the module
exports by mutation," e.g.:
// mypolyfill.js
...
if (!SomeBuiltinModule.newFeature) {
load("someotherlib.js", function(x) {
SomeBuiltinModule.newFeature = x;
});
}
you instead say "let the polyfill provide the exports," e.g.:
// mypolyfill.js
...
export let newFeature = SomeBuiltinModule.newFeature;
if (!newFeature) {
load("someotherlib.js", function(x) {
newFeature = x;
});
}
The difference is that clients import from the polyfill instead of importing
from the builtin module. I'm not 100% satisfied with this, but it's not any
more code than monkey-patching.
Dave
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