Re: What is gained by the extra level of map indirection recommended in help?

On Saturday, December 10, 2016 at 11:32:33 AM UTC-6, Andy Wokula wrote:
> Am 29.11.2016 um 20:18 schrieb Brett Stahlman:
> > The 'write-plugin' section of the help recommends the following
> > 3-level map approach:
> >
> > map ,c <Plug>TypecorrAdd
> > noremap <unique> <script> <Plug>TypecorrAdd <SID>Add
> > noremap <SID>Add :call <SID>Add(expand("<cword>"), 1)<CR>
> >
> > I understand how it works, but it wasn't immediately clear to me what
> > was being gained by the middle level of indirection: specifically the
> > map to <SID>Add. What is the advantage of this strategy over the
> > following 2-level approach?
> >
> > map ,c <Plug>TypecorrAdd
> > noremap <unique> <script> <Plug>TypecorrAdd
> > \ :call <SID>Add(expand("<cword>"), 1)<CR>
>
> Your "2-level approach" contains a mistake: `<script>' should be
> removed.

I see that it's not needed (given that there are no <SID> maps in the rhs), but how is it an error? IIUC, it simply inhibits remapping, which is already inhibited by the "noremap".

>
> > The help says...
> > "If another script would also map <SID>Add, it would get another
> > script ID and thus define another mapping."
> >
> > While this is true, isn't this sort of script-uniqueness already
> > guaranteed by the use of <SID> in the rhs of the 3rd mapping? I.e.,
> > :call <SID>Add(...)<CR>
>
> It is.
>
> `<script>' controls "remapping", not "script-uniqueness".
>
> There is ":map" (remapping on) and ":noremap" (remapping off) and then
> there is ":noremap <script>" (remapping on for <SID> maps, remapping off
> otherwise). ":map <script>" can be used also, it's the same.

Understood. Thanks. The confusion stemmed from my mistaken assumption that the purpose of the <SID>Add map went beyond simple code reuse - that it was required for mapping "hygiene". (It would have been more obvious if I'd noticed that in the Vim example, <SID>Add appeared in 2 distinct right hand sides: both <Plug>TypecorrAdd and menu item 'Plugin.Add Correction'...)

Thanks,
Brett Stahlman

>
> --
> Andy

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