Backspace is not working properly in the output window

[glebovmaksim]

Sometimes it deletes the prompt itself. Here is the gif.

Was surprised that it actually worked on the first expression, but after trying to remove an empty brackets it started to fail every time.

[bpringe]

I'm unable to reproduce. What's your OS? And what version of Calva are you on? In version 2.0.110 backspacing through the prompt is not allowed. I also see a space being added after your evaluation result, which doesn't happen for me.

[bpringe]

I see now that you're saying the disabling of backspace is not being respected after deleting the empty list. But again, I cannot repro. =(

[glebovmaksim]

OS: Ubuntu 18.04.1.
Calva: 2.0.110. Reinstallation did not help =(

Some additional information:

• It happens after deleting any empty datastruct affected by Paredit.
• Since deleting the empty datastruct is the last step of deleting every form in Paredit, the problem becomes worse.
• In Cave Man Paredit mode backspacing always works, no restrictions at all.

Sometimes it does work, but mostly not. Could it be some concurrency problem?

[PEZ]

It's interesting that the whole buffer seems to break the syntax highlighting... What other extensions are you using? I've seen Clover conflicting.

[PEZ]

I can reproduce this. Very interesting!

[PEZ]

When deleting the empty list, all trailing spaces in the window are deleted. My mind is blown.

[bpringe]

I can reproduce now too. Weird.

[PEZ]

And now I can't reproduce it any longer. So strange!

[glebovmaksim]

Let me show you something crazy. It's even reproducible!

[glebovmaksim]

Another random weird thing. Disappeared after cleaning the file.

[gustavobertolino]

Same behavior here : (

It doesn't affect any part of my code, neither the IDE, but it something bad from the user experience point of view.

[glebovmaksim]

@PEZ, @bpringe, I've found the source of the problem. This behavior occurs because Calva formats the entire file, which happens in two cases:

• After removing any root pair paranthesis (because of this and this). I doubt it's intentional, maybe it should be fixed. Please correct me if I'm wrong.
• By pressing tab on an empty line. This is fine in a regular file, but in the output file it deletes all trailing spaces next to prompt and breaks it. I think we should not allow to format the entire output file at all, because on a longer session it may grow to a large size, resulting in (possible) slow formatting. And it doesn't seem like a useful feature here.

I can send a pull request if you point me in the right direction to fix this 😄

[PEZ]

Ah, yes, that makes sense! I was looking at the wrong place...

So, many paredit commands finish with formatting and probably we (implicitly or explicitly) tell the formatter to trim trailing whitespace.

Iirc there is a special case for when formatting is performed on the top level. Or, rather, for selecting what is to be formatted. A check there for if it is the output file could maybe stop this madness. Also trimming trailing whitespace is generally a bad idea in this window.

PR is super welcome. Please don't hesitate to ask us for help.

[bpringe]

@glebovmaksim Great find! Looks like you're looking in the right places already, though I haven't messed with the formatting much myself.

@PEZ Maybe when formatting, if it's the repl file, we should only format up to the previous prompt?