Re: [docs] [bitbake-devel] [PATCH] doc: Mention `if [[ somecondition ]]` is not supported

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Tue, 2025-03-25 at 18:30 +0100, Quentin Schulz wrote:
> Hi Richard,
> 
> On 3/25/25 11:14 AM, Richard Purdie wrote:
> > On Tue, 2025-03-25 at 11:04 +0100, Quentin Schulz via lists.yoctoproject.org wrote:
> > > 
> > > 
> > > On 3/20/25 1:33 AM, Javier Tia via lists.openembedded.org wrote:
> > > > I keep forgetting using `if [[ somecondition ]]` is not supported.
> > > > 
> > > > Signed-off-by: Javier Tia <javier.tia@linaro.org>
> > > > ---
> > > >    doc/bitbake-user-manual/bitbake-user-manual-metadata.rst | 4 ++++
> > > >    1 file changed, 4 insertions(+)
> > > > 
> > > > diff --git a/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst b/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
> > > > index 415fbf6d6..5474e154f 100644
> > > > --- a/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
> > > > +++ b/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
> > > > @@ -1381,6 +1381,10 @@ To make use of this technique, you need the following things in place:
> > > >       To call your modified version of the function as defined in your recipe,
> > > >       call it as ``do_foo``.
> > > >    
> > > > +   .. note::
> > > > +
> > > > +      Conditional expression using ``[[ somecondition ]]`` is not supported.
> > > > +
> > > 
> > > Do you know what the reason is for that limitation?
> > > 
> > > The example above this git context is not really implying `[[
> > > somecondition ]]` would be valid though.
> > > 
> > > If I remember correctly, the shell functions are run by /bin/sh
> > > interpreter, so it depends on which shell you have configured by default
> > > in your system. Is it possible this is due to you being used to develop
> > > with bash where this is possible and having your Yocto build run with a
> > > different shell (e.g. dash, which doesn't seem to support that? c.f.
> > > https://manned.org/dash.1)?
> > > 
> > > I think we should recommend people write POSIX-compliant shell functions
> > > and tasks rather no?
> > 
> > Bitbake parses the shell functions and our shell parser can't cope with
> > certain syntax unfortunately.
> > 
> 
> Ah, I see. This happens before the shell even runs the code. Do we 
> happen to have a list of things/syntax we cannot parse?

There are open bugs. I did recently run into backgrounding not working
in the pseudo reproducer so I just used a separate script. Not sure we
want to support background processes though.

> I think it therefore deserves a bigger place than a small note, maybe
> e.g. a sub(sub...)section of limitations?

Patches welcome!

Cheers,

Richard