CodeMirror tag insert and selection problem (Wikipedia editor with MW syntax highlighting)

[Eccenux]

CodeMirror is used for syntax highlighting on Wikipedia (for wikicode).

Test code:

setTimeout(function(){
	console.log('2 sek')
},7000)
setTimeout(function(){
	console.log('1 sek')
},8000)
setTimeout(function(){
	sel_t3.insertText('<b>', '</b>', 'bold')
},9000)

Edit field before insertText ("d.e.f" is selected):

a
b
c
d
e
f
g
h

After:

a
b
c<b>d

e

f</b>
g
h

Problem is from invalid selection text (note double \n):

{ isEditable: true, isInput: false, selected: "d\n\ne\n\nf" }

[Eccenux]

On Windows this used to return multiple \r\n, which made things worse (added new line and space upon insert). But fixed that in 3.0.1.

[Eccenux]

Not a CodeMirror bug. It is fine on CM site (screen).

It's a bug in CM from MediWiki or some plugins loaded for it.

Reported upstream:
https://phabricator.wikimedia.org/T321144

[Eccenux]

Should be fixed by update to CM6:
T259059 Upgrade to CodeMirror 6