[PATCH] Update doc: No :normal cursor movement in indentexpr

[Sung Pae]

The documentation explicitly states that moving the cursor is okay in
an indentexpr, but this is only true when moved directly with cursor(),
setpos(), search(), etc. Moving the cursor via `normal! w` has side
effects that frustrate the attempts of get_expr_indent() to restore the
original cursor position. However, this is not apparent without reading
the source.

For example:

function! BadIndentExpr()
normal! $
return 8
endfunction
setlocal indentexpr=BadIndentExpr()

The cursor position is not restored when indenting the current line.
---
runtime/doc/options.txt | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 3beb2b0..b0ea21c 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4162,7 +4162,8 @@ A jump table for the options with a short description can be found at |Q_op|.
and |lispindent()|.
The evaluation of the expression must not have side effects! It must
not change the text, jump to another window, etc. Afterwards the
- cursor position is always restored, thus the cursor may be moved.
+ cursor position is always restored, thus the cursor may be moved (but
+ not via |:normal| commands).
Normally this option would be set to call a function: >
:set indentexpr=GetMyIndent()
< Error messages will be suppressed, unless the 'debug' option contains
--
1.8.1.2

[Bram Moolenaar]

Sung Pae wrote:

> The documentation explicitly states that moving the cursor is okay in
> an indentexpr, but this is only true when moved directly with cursor(),
> setpos(), search(), etc. Moving the cursor via `normal! w` has side
> effects that frustrate the attempts of get_expr_indent() to restore the
> original cursor position. However, this is not apparent without reading
> the source.
>
> For example:
>
> function! BadIndentExpr()
> normal! $
> return 8
> endfunction
> setlocal indentexpr=BadIndentExpr()
>
> The cursor position is not restored when indenting the current line.

I rather fix the problem than updating the documentation.
You say you read the source code, can you pinpoint why the cursor is not
restored when using :normal?


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[Sung Pae]

On Sat, Feb 09, 2013 at 02:10:36PM +0100, Bram Moolenaar wrote:

> I rather fix the problem than updating the documentation.

Sounds great; I mispredicted your response.

> You say you read the source code, can you pinpoint why the cursor is
> not restored when using :normal?

:normal commands update curwin->w_curswant and curwin->w_set_curswant,
which beginline() uses to set the cursor position. op_reindent calls
beginline() with the BL_SOL flag set, so this bug only appears when
'nostartofline' is set (which I didn't notice before).

Attached patch simply saves and restores both settings after the
'indentexpr' evaluation.

Thank you,
Sung Pae

[Bram Moolenaar]

Sounds right. Thanks for the patch!


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