fix(util): suppress 'press ENTER' in echo_messages()

[sam-mccall]

This is used for workspace/showMessage, when it contains multiple lines.
Using echomsg in a loop means that each line after the second prompts
before displaying.

The downside of this change is if there are multiple consecutive calls
to echo_messages(), only the last one is shown. (All will appear in :messages)

Motivating use: clangd has "dump AST" code action behind the
-hidden-features flag. This action calls showMessage with a payload like:

FunctionDecl 0x14387ee101e8 </home/sammccall/test.cc:1:1, line:3:1> line:1:6 foo 'void ()'
`-CompoundStmt 0x14387ee10380 <col:11, line:3:1>
  `-DeclStmt 0x14387ee10368 <line:2:3, col:10>
      `-VarDecl 0x14387ee10300 <col:3, col:7> col:7 bar 'int'

[chemzqm]

I can't reproduce 'press ENTER' behavior, we use :echom to make sure user can get it from :messages.

[sam-mccall]

I can't reproduce 'press ENTER' behavior

@chemzqm What did you try? Running :call coc#util#echo_messages(...) directly won't reproduce it, as vim defers "press ENTER" if the command-line is open.

This should do it though:
:call timer_start(1000, { tid -> coc#util#echo_messages('', ['foo','bar','baz'])})

we use :echom to make sure user can get it from :messages.

This patch still does that, it uses echom to send the message to :messages (with no prompt), and additionally echo to print all the lines at once (with a single prompt)

[fannheyward]

:call timer_start(1000, { tid -> coc#util#echo_messages('', ['foo','bar','baz'])})

doesn't reproduce press ENTER.

[sam-mccall]

You're right, sorry was AFK. let me get a proper reproducer.

[sam-mccall]

OK, so far the only way I've been able to reproduce this is with an actual language server sending a multiline workspace/showMessage.

e.g. with coc-clangd:

• add "clangd.arguments": ["-hidden-features"] to coc-settiongs.json
• create a file with void foo() { int bar; }
• at start-of-file, :call CocActionAsync('codeAction','')
• select "Dump FunctionDecl AST"

The patch definitely fixes this for vim 8.1.2269.

It seems I should be able to create the same effect by calling echo_messages from either an autocmd or a timer, but I can't and I'm not sure why.

[fannheyward]

@sam-mccall no press ENTER in nvim with your test case.

[sam-mccall]

@fannheyward Indeed, I got nvim set up and verified it's broken in a different way than vim :-)

	master	with this patch
vim 8.1.2269	'press ENTER' after each line	shows all lines at once
nvim v0.5.0-418-g87d892afa	displays only the last line	shows all lines at once

(Both with an empty config other than coc.nvim, coc-clangd, coc-settings.json as described above, and set nocompatible | syntax on for vim)

[fannheyward]

Reproduced, I prefer to add this patch.

@chemzqm in this case, workspace.showMessage('aa\nbb\ncc\ndd') will only show dd on master, with this patch, will show the full message.

[sam-mccall]

Thanks!