vim-patch:8.2.2612: col('.') may get outdated column value

Problem:    col('.') may get outdated column value.
Solution:   Add a note to the help how to make this work and add a test for
            it. (closes vim/vim#7971)
https://github.com/vim/vim/commit/18b7d86d7fa997bbb02a069dafacb32a0f73ca1e

1 files changed, 14 insertions, 0 deletions

diff --git a/runtime/doc/map.txt b/runtime/doc/map.txt
index edec4a8de7..3ee26b0817 100644
--- a/runtime/doc/map.txt
+++ b/runtime/doc/map.txt
@@ -224,6 +224,20 @@ text before the cursor and start omni completion when some condition is met.
 For abbreviations |v:char| is set to the character that was typed to trigger
 the abbreviation.  You can use this to decide how to expand the {lhs}.  You
 should not either insert or change the v:char.
+ 
+Also, keep in mind that the expression may be evaluated when looking for
+typeahead, before the previous command has been executed.  For example: >
+	func StoreColumn()
+	  let g:column = col('.')
+	  return 'x'
+	endfunc
+	nnoremap <expr> x StoreColumn()
+	nmap ! f!x
+You will notice that g:column has the value from before executing "fx",
+because "z" is evaluated before "fx" is executed.
+This can be solved by inserting <Ignore> before the character that is
+expression-mapped: >
+	nmap ! f!<Ignore>x
 
 Be very careful about side effects!  The expression is evaluated while
 obtaining characters, you may very well make the command dysfunctional.