Re: [bitbake-devel] [PATCH RFC] parse/ast: add support for additive built-in fragments

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

On Tue, 2026-09-01 at 09:52 +0200, Antonin Godard via lists.openembedded.org wrote:
> Add support for the following syntax specified in a fragment list
> definition:
> 
>   fragmentname:VARIABLE:add
> 
> Setting this fragment appends to VARIABLE instead of setting its value.
> This does not break pre-existing fragments which still set a variable's
> value entirely.
> 
> For example, in OE-Core consider the following definition:
> 
>   OE_FRAGMENTS_BUILTIN = "class:INHERIT:add"
> 
> Then one could specify the following:
> 
>   OE_FRAGMENTS = "class/buildstats class/rm_work"
> 
> Which would result in appending " buildstats rm_work" to the INHERIT
> variable.
> 
> This would also allow bitbake-setup configurations to come with a list
> of pre-enabled classes, for example.
> 
> Note: The "add" suffix was chosen in the definition to avoid confusion
> with the existing "append" usage in Bitbake.
> 
> Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
> ---
> Note: The bitbake-config-build OE-Core utility would require adaptations
> as it currently removes any pre-existing built-in fragment with the
> same suffix. I can also send the associated OE-Core patches.
> 
> Note 2: We could also have these fragments specified as:
> 
>   OE_FRAGMENTS = "class/add/buildstats class/add/retain"
> 
> To avoid confusing them with original built-in fragments. While I
> agree it disambiguates them from original built-ins, I also think from a
> user point of view, being able to set:
> 
>   OE_FRAGMENTS = "machine/qemuarm distro/poky class/buildstats class/retain"
> 
> feels a bit more natural. Discussion is open :)


It is definitely an interesting one and the syntax isn't too bad.. Are
there uses beyond class inherit though?

machine/distro were added as they are clear variables in common use
which avoided tons of boilerplate in layer definitions. Do we have
similar needs here or are these inherits better captured in config
fragments?

Cheers,

Richard