[U-Boot] [PATCH 0/2] cmd: auto-complete args starting with a $

[Wolfgang Denk <wd@denx.de>]

Dear Boris,

In message <20181204105448.63b9af8c@bbrezillon> you wrote:
>
> > > It's pretty common to pass arguments that start with a $ and are then
> > > expanded by the shell, and I'm this kind of lazy guy that hits tab all
> > > the time and expects the shell to suggest something appropriate. So
> > > here is a patchset adding support for ${} auto-completion and using the
> > > new helper from the mtd command.  
> > 
> > You mean, this feature depends on MTD support?  this is not goot.
>
> Not at all, MTD is just the first user of this dollar_complete()
> helper. That's what I meant.

But is this not based on the code of mtd_name_complete() which is
only availabole when MTD is present?

> > Also, you should make this feature configurable.  Not everybody may
> > want to use it or may have the memory available.
>
> It already depends on CONFIG_AUTO_COMPLETE, and each command has to
> explicitly call the helper to support ${} auto-completion. Not that $
> auto-completion only makes sense for some arguments, not all of them.
> It's the responsibility of the command itself to decide when it should
> be used.

Um... this is not hat I would expect - if we implement
auto-completion for variables, it should IMO work similar to what a
standard shell is doing.

In Bash, I can do:

-> foo=1234
-> echo $f<TAB>
$f     $flag  $foo
-> echo $f

i. e. this is a feature of the shell and not of any command.
Implementing this a zillion times for each of the commands in
inacceptable.  Also, implementing it for one command and not for
another makese no sense - that would violate the Principle of Least
Surprise, as you have something which looks convenient but does not
work everywhere.

> > Technically - should autocompletion not be prevented for escaped
> > '$' characters, i. e. hitting TAB after a '\$' sequence should NOT
> > expand?
>
> It's already the case. The argument has to start with $ or ${ to be
> auto-completed.

We should implement this such that behaviour is similar to what we
see on a standard shell.

Best regards,

Wolfgang Denk

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