Adds '--clear-screen' option to clear screen between watch runs

[colinta]

This is very slapped together, but I wanted it for myself and figured I'd start the conversation. If you are even open to mergin it let me know of any changes.

Usage:

npm test ava --watch --clear-scren 

What does this PR change?

Between test runs, it sends this.lineWriter.write(ansiEscapes.clearTerminal), which clears the screen and scrollback buffer on all the terminal apps I have handy.

I promoted this same behaviour in TypeScript, I guess it's my hill to die on 🤣 (in that case, --watch was already clearing the screen, this just changed/improved the behaviour).

Jest also clears the screen when using --watch. I prefer it, FWIW, but I've read the argument for keeping all those logs... I'm not convinced, but hey that's just me. I'd be happy w/ --clear-screen though it isn't exactly very discoverable atm.

WDYT?

[colinta]

When I first wrote this, I used process.stderr.write('\x1b[2J\x1b[H\x1b[3J');, but that felt wrong given the use of this.lineWriter.write so I switched to that... but now it doesn't work, so I switched it back to process.stderr.write. 🤷‍♂️

Correction: it works fine using lineWriter.

[sindresorhus]

I have no opinion whether this should be added, but the flag should be --clear-screen.

[colinta]

I'm not personally a fan of the more verbose --clear-screen – I chose cls for what I thought was a good reason – but I won't quibble. 🙂 (edit: that article points out that in *nix, the equivalent command would be clear, but I like --clear even less than --clear-screen, so --clear-screen is a decent compromise at the end of the day, and in the absence of other arguments, verbose/clarity beats all)

I gave this a short alias of -C, btw. Like/dislike? I'm not stuck on it.

[novemberborn]

Yea I don't mind this. Our long-form flags are not abbreviated so 👍 on --clear-screen.

Do we want to keep this as a CLI flag only or also support it in the configuration?

Testing wise, this could be a permutation of

ava/test-tap/reporters/default.js

Line 45 in 024de32

t.test('default reporter - watch mode run', run('watch'));

which should include the ansi code in the generated reporter logs. Let me know if you need a pointer on how to regenerate those, it's far from ideal.

[novemberborn]

Maybe move this down into the if (this.watching && !plan.firstRun) line below? It better connects clearScreen with watch mode plus maybe there's no need to clean the terminal on the first run? Or does that get weird?

[colinta]

I had it somewhere down there to start, but then it occurred to me that --clear-screen without --watch had no effect at all, which simply felt "unhandled". Why not have it clear the screen? 🤔

Since then I've been actually using it without the watch flag just as often as with it.

[colinta]

Thanks for the pointers, I'll try to get those tests updated, and yes having it config makes sense 👍