bug#48500: 28.0.50; url-retrieve-synchronously exits abnormally due to pending keyboard input from terminal

[Shane Mulligan <mullikine@gmail.com>]

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Hi Eli,

I tagged you back in this conversation because I may have fixed the issue
:).

Shane Mulligan

How to contact me:
🇦🇺 00 61 421 641 250
🇳🇿 00 64 21 1462 759 <+64-21-1462-759>
mullikine@gmail.com


On Wed, May 19, 2021 at 6:48 PM Shane Mulligan <mullikine@gmail.com> wrote:

> I may have resolved this issue with the following patch to
> `url-retrieve-synchronously`.
> What this achieves is to trigger a `quit` in a controlled environment
> rather than allowing it to occur when `accept-process-output` is run.
> It's not always wanted to trigger a quit when `(input-pending-p)` is `t`.
> But I noticed from placing `while-no-input` around `accept-process-output`
> to avoid the `quit` that `url-retrieve-synchronously` would then hang but
> with the controlled `quit` happening beforehand, `accept-process-output` no
> longer needs `while-no-input` around it. The end result is buttery smooth
> helm with no accidental `quit` from typing too fast. I think this may have
> resulted in GUI helm faster too.
>
> ```
> 29c29,30
> <       (let ((proc (get-buffer-process asynch-buffer)))
> ---
> >       (let ((proc (get-buffer-process asynch-buffer))
> >             (counter 0))
> 71a73,78
> >             (with-local-quit
> >               (if (input-pending-p)
> >                   (progn
> >                     (setq counter (1+ counter))
> >                     (if (> counter 20)
> >                         (keyboard-quit)))))
> ```
> Shane Mulligan
>
> How to contact me:
> 🇦🇺 00 61 421 641 250
> 🇳🇿 00 64 21 1462 759 <+64-21-1462-759>
> mullikine@gmail.com
>
>
> On Wed, May 19, 2021 at 11:32 AM Shane Mulligan <mullikine@gmail.com>
> wrote:
>
>> My apologies. It was literally 5am when I wrote that. I think I have
>> misunderstood `C-g` being generated with `quit-flag`. The bad behaviour is
>> very clearly still happening. I will try to clarify this problem further by
>> experimenting with it. I need to figure out why `while-no-input` suppresses
>> the `quit` but merely setting `quit-flag` does not. Something indirect may
>> be happening.
>>
>> Thank you all,
>> Shane Mulligan
>>
>> How to contact me:
>> 🇦🇺 00 61 421 641 250
>> 🇳🇿 00 64 21 1462 759 <+64-21-1462-759>
>> mullikine@gmail.com
>>
>>
>> On Wed, May 19, 2021 at 4:54 AM Eli Zaretskii <eliz@gnu.org> wrote:
>>
>>> > From: Shane Mulligan <mullikine@gmail.com>
>>> > Date: Wed, 19 May 2021 04:32:16 +1200
>>> >
>>> > Thanks for looking into this so quickly. First some background on the
>>> problem. I managed to work through
>>> > this issue (https://github.com/emacs-helm/helm/issues/2417) with the
>>> `emacs-helm` maintainer and we
>>> > found what appears to be that the call to `accept-process-output`
>>> inside of `url-retrieve-synchronously` will
>>> > generate a `C-g` when there is pending input of any char. As far as I
>>> can tell this is an issue only with
>>> > terminal emacs. As I understand it, `inhibit-quit`, as used in
>>> `accept-process-output` allows a `C-g` to be
>>> > propagated outwards and handled and from what I can see by the
>>> comments surrounding,
>>> >
>>> > ```
>>> >               ;; accept-process-output returned nil, maybe because the
>>> process
>>> >               ;; exited (and may have been replaced with another).  If
>>> we got
>>> >               ;; a quit, just stop.
>>> > ```
>>> >
>>> > the `C-g` in this case is expected.
>>> >
>>> > But I wonder if `C-g` was meant to be generated if the user was simply
>>> mashing keys on the keyboard.  In
>>> > this case, the `C-g` emanating from `accept-process-output` was
>>> bubbling up into `helm` and `helm` was
>>> > treating it like an error.
>>> >
>>> > Here, you can see a quit being generated from the visual cue in the
>>> minibuffer.
>>> > https://asciinema.org/a/nAIB8Z1lGgZJqJg9Mt8YiNEM9
>>> >
>>> > Here, I have added `while-no-input` and I no longer get the `quit`.
>>> > https://asciinema.org/a/x9ELZhwDP1IUtmOz0M1cly42H
>>> >
>>> > However, as I test the addition of `while-no-input` with
>>> `helm-google-suggest` (as above), though Quit is no
>>> > longer being generated from mashing keys, the key input which would
>>> have generated the `quit` is not
>>> > immediately shown in `helm`. Instead, it only appears on the next key
>>> press. So my implementation may not
>>> > be perfect or complete.
>>> >
>>> > Finding the solution would make the minibuffer far less interrupted
>>> while typing when
>>> > `url-retrieve-synchronously` is used in the background.
>>> >
>>> > Thank you.
>>> >
>>> > Shane Mulligan
>>>
>>> Please in the future send your responses with the bug address,
>>> 48500@debbugs.gnu.org, on the CC list, so that others will see your
>>> detailed descriptions.  I won't have time to take a good look into
>>> that in the next few days, so it's good to make others aware of your
>>> findings, because they might look into it meanwhile.
>>>
>>> Personally, I find it very strange that typing on the keyboard
>>> produces C-g, it shouldn't happen, neither on a TTY nor on a GUI
>>> display.
>>>
>>

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