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 may get outdated column value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 may get outdated column value.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 #7971)
diff --git a/runtime/doc/map.txt b/runtime/doc/map.txt
index bf39130..873d5d6 100644
--- a/runtime/doc/map.txt
+++ b/runtime/doc/map.txt
@@ -263,6 +263,20 @@
endfunc
nnoremap <expr> <F3> <Sid>OpenPopup()
+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.
For this reason the following is blocked: