Breaks line without leaving insert mode

Question

With the textwidth option set the text written can be wrapped when we leave insert mode. If I type a line longer than my textwidth value then it will go on a new line.

e.g. with set textwidth=5 and set linebreak :

1 2 3 [4]

1 2 3
4[]


lorem ipsum dolor[Esc]

lorem 
ipsum 
dolor[]

[X] means: I press X where [] is.

So when entering a line of number spearated by space, at the moment I enter the 6th character (in this case the number 4) the line break.

But when I enter a sentence the line doesn't break until I quit insert mode.

Do you know what I can try/set ?

Answer 1

So as we troubleshooted in the comments the problem came from the formatoption value.

According to :h formatoptions :

This is a sequence of letters which describes how automatic formatting is to be done.

Your settings contained the letter l which according to :h fo-table does the following:

Long lines are not broken in insert mode: When a line was longer than 'textwidth' when the insert command started, Vim does not automatically format it.

So the solution is to use the following command set fo-=l. Still according to the doc it is better to use the += and -= features options of set to avoid conflicts with tags added later.

Another important point is how these tags are set: a lot of filetypes set those tags automatically. For example in [path_to_vim_installation]/vim74/ftplugin/c.vim you can read:

" Set 'formatoptions' to break comment lines but not other lines,
" and insert the comment leader when hitting <CR> or using "o".
setlocal fo-=t fo+=croql

A solution is to override those behavior in your .vimrc for the filetypes that you want.

Answer 2

Check that your formatoptions contain at least the letters 't' and 'c'.

Make sure paste mode is not set, otherwise all insert mode mappings and formatting is disabled. You can tell is paste mode is set if the -- INSERT (paste) -- prompt appears at the when in insert mode rather than just -- INSERT --. Paste mode can be disabled with :set nopaste.

Otherwise try running Vim with the command vim -u NONE and see if the problem still occurs, this fixes the problem it is an issue with your vimrc file or a plugin.