Does b:undo_ftplugin actually work? - vim_dev

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Message from discussion Does b:undo_ftplugin actually work?
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Message-Id: <201211152132.qAFLW82O022116@masaka.moolenaar.net>
To: Christian Brabandt <cbli...@256bit.org>
Cc: vim_dev@googlegroups.com
Subject: Re: Does b:undo_ftplugin actually work?
In-Reply-To: <20120928122127.GA19...@256bit.org>
From: Bram Moolenaar <B...@Moolenaar.net>
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Date: Thu, 15 Nov 2012 22:32:08 +0100
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Christian Brabandt wrote:

> On Do, 27 Sep 2012, Gary Johnson wrote:
> 
> > On 2012-09-27, ZyX wrote:
> > > ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½, 28 ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 2012 ï¿½., 8:04:05 UTC+4 ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Gary Johnson ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½:
> > > > I was working on some code that set b:undo_ftplugin, but it didn't
> > > > have any effect when I set a new filetype.  I copied
> > > > $VIMRUNTIME/ftplugin.vim to ~/.vim and instrumented the section that
> > > > is supposed to execute b:undo_ftplugin.
> > > > 
> > > >       func! s:LoadFTPlugin()
> > > >         echo "In s:LoadFTPlugin()" | sleep 2
> > > >         echo "b:undo_ftplugin is" b:undo_ftplugin | sleep 2
> > > You should've put this line after the next one (or, better, remove
> > > it as absense of the next message will indicate absence of
> > > b:undo_ftplugin definition). And use ":echom", not ":echo |
> > > sleep", then all messages will be seen when you do ":messages"
> > > >         if exists("b:undo_ftplugin")
> > > >           echo "b:undo_ftplugin exists" | sleep 2
> > > >           exe b:undo_ftplugin
> > > >           unlet! b:undo_ftplugin b:did_ftplugin
> > > >         endif
> > > > 
> > > > Whenever I open a new file for which Vim can detect the filetype, or
> > > > :edit some file, I always get the following errors.
> > > b:undo_ftplugin is defined in filetype plugins. What else do you
> > > expect? When opening new file and doing :edit buffer scope is
> > > clean and filetype plugins are loaded by s:LoadFTPlugin function
> > > *after* you test for b:undo_ftplugin. You should have used "set
> > > filetype=new_filetype" on *existing* buffer to trigger desired
> > > behavior.
> > > 
> > > >     Error detected while processing function <SNR>5_LoadFTPlugin:
> > > >     line    2:
> > > >     E121: Undefined variable: b:undo_ftplugin
> > > >     E15: Invalid expression: b:undo_ftplugin | sleep 2
> > > > 
> > > > That is even after I execute
> > > > 
> > > >     :echo b:undo_ftplugin
> > > > 
> > > > and verify that it is set correctly according to the new filetype.
> > > Don't use :edit. It wipes the buffer.
> > > 
> > > > It seems that b:undo_ftplugin does not exist in the environment in
> > > > which s:LoadFTPlugin() is executed.  Does setting b:undo_ftplugin as
> > > > most current ftplugin scripts do actually do anything?
> > > They do. Use "set filetype=new_filetype".
> > 
> > Thanks for the reply, but I see that I didn't explain the problem
> > very well.  Also, some of my experiments created new buffers instead
> > of replacing the contents of existing buffers with new filetypes, so
> > I wasn't replicating the actual problem conditions.
> > 
> > Let me try again.
> > 
> > The actual problem is that I would like to set 'indentexpr' for
> > buffers with no 'filetype' so that I get indenting behavior that I
> > think might be useful when just opening Vim and typing notes.  To
> > that end I put the following in my ~/.vimrc.
> > 
> >     au BufWinEnter * if &ft == "" || &ft == "text"
> >          \ |     setlocal indentexpr=indent(prevnonblank(v:lnum-1))
> >          \ |     setlocal indentkeys-=o
> >          \ |     let b:undo_ftplugin = "setl inde< indk<"
> >          \ | endif
> > 
> > When I start vim and execute
> > 
> >     :echo b:undo_ftplugin
> > 
> > I see
> > 
> >     setl inde< indk<
> > 
> > as expected.  Further, ":ls" shows
> > 
> >   1 %a   "[No Name]"                    line 1
> > 
> > Now, if I open a C file, I expect to have 'indentexpr' empty, either
> > because the C file is opened in a new buffer or because the C file
> > was opened in the same buffer and the b:undo_ftplugin was executed.
> > However, after executing
> > 
> >     :e foo.c
> >     :set indentexpr?
> > 
> > I see
> > 
> >       indentexpr=indent(prevnonblank(v:lnum-1))
> > 
> > and ":ls" shows
> > 
> >       1 %a   "foo.c"                        line 1
> > 
> > I did take your advice about using echom and instrumented
> > ftplugin.vim differently and verified that when it was executed by
> > the 'filetype' change to "c", b:undo_ftplugin did not exist.
> > 
> > If ":edit wipes the buffer" as you say, so that b:undo_ftplugin is
> > deleted, then shouldn't that wiping reset the values of any local
> > options?
> > 
> > I'm just looking for a way to reset those local options when I edit
> > a new file, b:undo_ftplugin seemed to be the way to do it, but it
> > doesn't seem to do anything useful.
> >  
> > Not using :edit is not a solution.  For example, if I start vim
> > and use ":MRU" to open a recently-used C file, I wind up with
> > 'indentexpr' set as above, which wrongly indents C.
> 
> Hi Gary,
> 
> Looks like the initial buffer isn't correctly freed.
> Try this patch: which at least also gets rid of the buffer local 
> options, when loading another buffer:
> diff --git a/src/buffer.c b/src/buffer.c
> --- a/src/buffer.c
> +++ b/src/buffer.c
> @@ -1702,6 +1702,12 @@
>  #endif
>         /* buf->b_nwindows = 0; why was this here? */
>         free_buffer_stuff(buf, FALSE);  /* delete local variables et al. */
> +       /* can't set TRUE in free_buffer_stuff(), this would destroy the wininfo stuff,
> +        * so freeing the buffer options here afterwards manually */
> +       free_buf_options(buf, TRUE);
> +#ifdef FEAT_SPELL
> +       ga_clear(&buf->b_s.b_langp);
> +#endif
>  #ifdef FEAT_KEYMAP
>         /* need to reload lmaps and set b:keymap_name */
>         curbuf->b_kmap_state |= KEYMAP_INIT;
> 
> Although, this doesn't solve the problem, that the b:undo_ftplugin 
> option isn't executed on BufUnload event. Possibly we need a global 
> BufUnLoad event, that takes care of this, e.g. something like this:
> 
> " Make sure, the b:undo_ftplugin is also executed deleting the buffer
> BufUnload * if exists("b:undo_ftplugin") | exe b:undo_ftplugin | endif
> 
> But I am not sure, where to put this script. Perhaps also put this into 
> ftplugin.vim?

I finally had time to look into this patch.  It breaks the tests in a
nasty way.  Thus this is not the right solution. Instead of freeing the
options they should be initialized to the global values.
Perhaps setting buf->b_p_initialized to FALSE works?

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