Keep in mind `let A = A;` is a TDZ error in any real ES6 environment. The example I posted works properly with Babel's live-binding implementation and should require less repetition. What were your thoughts on it?
On Thu, Aug 11, 2016 at 12:23 AM, /#!/JoePea <[email protected]> wrote: > Alright, so I believe I have found the solution. It is not possible to > guarantee a certain module evaluation order, but using some clever (but > tedious) conditional checking I believe the problem is solved (with two > caveats listed after): > > ```js > // --- Entrypoint > import A from './A' > console.log('Entrypoint', new A) > ``` > > ```js > // --- Module A > > import C from './C' > import {setUpB} from './B' > > let A > > export > function setUpA(C) { > > if (!A) { > A = class A extends C { > // ... > } > } > > } > > if (setUpA && C) setUpA(C) > if (setUpB && C) setUpB(C) > > export {A as default} > ``` > > ```js > // --- Module B > > import C from './C' > import {setUpA} from './A' > > let B > > export > function setUpB(C) { > > if (!B) { > B = class B extends C { > // ... > } > } > > } > > if (setUpA && C) setUpA(C) > if (setUpB && C) setUpB(C) > > export {B as default} > ``` > > ```js > // --- Module C > > import A, {setUpA} from './A' > import B, {setUpB} from './B' > > class C { > constructor() { > // this may run later, after all three modules are evaluated, or > // possibly never. > console.log(A) > console.log(B) > } > } > > if (setUpA && C) setUpA(C) > if (setUpB && C) setUpB(C) > > export {C as default} > ``` > > The caveat is that this fails in both Babel environments and in Rollup. > For it to work in Babel environments, `let A` and `let B` have to be > changed to `let A = A` and `let B = B`, as per the [fault in Babel's > ES2015-to-CommonJS implementation](https://github.com/meteor/meteor/ > issues/7621#issuecomment-238992688) pointed out by Ben Newman. And it > fails in Rollup because Rollup [isn't really creating live bindings]( > https://github.com/rollup/rollup/issues/845), which is fine in most > cases, but doesn't work with these circular dependencies. The Rollup output > does not create the C reference before it is ever used in the first pair of > conditional checks, unlike what (I think) would happen with real live > bindings (please correct me if wrong). To understand what I mean in the > case of Rollup, just run `if (FOO) console.log(FOO)` in your console, and > you'll get an error because FOO is not defined. Had the bindings been live, > then FOO *would* be defined. > > > > */#!/*JoePea > > On Wed, Aug 10, 2016 at 5:04 PM, /#!/JoePea <[email protected]> wrote: > >> I found a solution that works in environments compiled by Babel, using >> the [workaround suggested by Ben Newman](https://github.com/met >> eor/meteor/issues/7621#issuecomment-238992688): >> >> ```js >> // --- Module A >> >> import C from './C' >> >> let A = A // @benjamn's workaround applied >> >> export >> function setUpA(C) { >> >> A = class A extends C { >> // ... >> } >> >> } >> >> export {A as default} >> ``` >> >> ```js >> // --- Module B >> >> import C from './C' >> >> let B = B // @benjamn's workaround applied >> >> export >> function setUpB(C) { >> >> B = class B extends C { >> // ... >> } >> >> } >> >> export {B as default} >> ``` >> >> ```js >> // --- Module C >> >> import A, {setUpA} from './A' >> import B, {setUpB} from './B' >> >> let C = class C { >> constructor() { >> // this may run later, after all three modules are evaluated, or >> // possibly never. >> console.log(A) >> console.log(B) >> } >> } >> >> setUpA(C) >> setUpB(C) >> >> export {C as default} >> ``` >> >> ```js >> // --- Entrypoint >> >> import A from './A' >> console.log('Entrypoint', new A) // runs the console.logs in the C >> constructor. >> ``` >> >> >> Although that works in my environment which is compiled from ES6 modules >> to CommonJS by Babel, it [doesn't work in Rollup.js](http://goo.gl/PXXBKI), >> and may not work in other ES6 module implementations. >> >> Is there some solution that will theoretically work in any ES6 module >> environment? >> >> */#!/*JoePea >> > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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