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Run prompts asynchronously #482

xiaq opened this Issue Sep 17, 2017 · 4 comments


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xiaq commented Sep 17, 2017

Sometimes prompts can take a long time and will block the UI. In that case, Elvish can render the prompt as a placeholder (say "?") and update it when the function completes.

@xiaq xiaq added this to the 0.11 milestone Sep 17, 2017


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zzamboni commented Sep 18, 2017

This would be very nice, with a couple of considerations:

  • Don't use "?" - better cache the previous value and use that
  • Run asynchronously but not overlapping - otherwise we have a potential explosion of simultaneous number of prompt commands running at the same time.

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therealpxc commented Sep 18, 2017

Are there any shells that currently do this right? This would be a pretty nice feature and hugely increase the perceived 'performance' of Elvish for people who use VCS prompts.

@xiaq xiaq closed this in dd2d36a Nov 12, 2017


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xiaq commented Nov 12, 2017

Good news, this has landed in master. To see it in action, try this:

edit:prompt = { echo 'slow prompt'; sleep 1 }
edit:-prompts-max-wait = 0.05

Read dd2d36a for a detailed explanation and caveat.

zzamboni added a commit to zzamboni/dot-elvish that referenced this issue Nov 14, 2017

Removed caching and documented using org-mode
With Elvish now supporting prompt caching
(elves/elvish#482), I have removed the whole
caching implementation from the prompt, which was messy and unreliable.

I have also used the opportunity to write the code in literate
programming style, using org-mode. See for the fully
documented source code, from which chain.elv is generated.

For an excellent introduction to literate programming using org-mode, see

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zzamboni commented Nov 14, 2017

@xiaq this is great! I have vastly simplified my chain theme implementation thanks to this new feature.

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