Loose idea on "try import"

Isiah Meadows isiahmeadows at gmail.com
Sat Mar 2 03:38:35 UTC 2019


Personally, I find this a *bad* idea. Top-level `await` in modules
would solve this problem far more quickly and efficiently.

-----

Isiah Meadows
contact at isiahmeadows.com
www.isiahmeadows.com

On Fri, Mar 1, 2019 at 3:35 PM Ben Wiley <therealbenwiley at gmail.com> wrote:
>
> Has anyone seen anything like this done in another language (with static imports)? If so we could learn something maybe. I know you can conditionally import in Python but that's basically the same thing as .catch()ing dynamic import()s in JavaScript (except done synchronously).
>
> Ben
>
> Le ven. 1 mars 2019 15 h 26, Herby Vojčík <herby at mailbox.sk> a écrit :
>>
>> On 1. 3. 2019 18:35, Michał Wadas wrote:
>> > I don't think so, because:
>> >
>> >   * Using promises to import module is not always desirable
>> >   * This mechanism doesn't impact ability to statically analyze modules
>> >     if ifs are excluded - it can only increase resolution time.
>>
>> Yeah, if 'if's are excluded. That version with those ifs was what was
>> concerning. That actually needs runtime to do the work. I suppose until
>> it doesn't need the runtime, it's all ok.
>>
>> >
>> > On Fri, Mar 1, 2019 at 1:56 PM Herby Vojčík <herby at mailbox.sk
>> > <mailto:herby at mailbox.sk>> wrote:
>> >
>> >     On 1. 3. 2019 12:04, Michał Wadas wrote:
>> >      > Syntax:
>> >      >
>> >      > try import fs from 'fs'
>> >      >     else import fs from 'fs-polyfill'
>> >      >     else import fs from 'another-fs-polyfill'
>> >      >     else do nothing; // Not sure about syntax
>> >      >
>> >      >
>> >      > try import {watchDirectory} from 'fs'
>> >      >     else import {watchDirectory} from 'fs-polyfill'
>> >      >     else if(process.os === 'ExoticSystem') import
>> >     {watchDirectory} from
>> >      > 'another-fs-polyfill'
>> >      >     else throw Error('Your OS doesn\'t support watching
>> >     directories');
>> >
>> >     I am not an expert, but afaict ES module system was created to be
>> >     statically analysable and this bring uncertainity.
>> >
>> >     For that probably dynamic import() is there; and your usage should
>> >     await
>> >     for a promise that tries to load one then the other etc.
>> >
>> >     Herby
>> >
>> >      > Usages:
>> >      >
>> >      >   * Optional dependencies
>> >      >   * Polyfills
>> >      >
>> >      > Problems:
>> >      >
>> >      >   * This can prevent loading modules before execution if presence of
>> >      >     modules can't be proved statically
>> >      >   * else-if requires execution before loading module - can be dropped
>> >      >
>> >      >
>> >      > I don't have enough time and knowledge about modules to write actual
>> >      > proposal.
>> >
>>
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