On Tue, 2021-12-07 at 11:09 -0800, Andre McCurdy wrote:

On Tue, Dec 7, 2021 at 9:58 AM Richard Purdie <rpurdie@...> wrote:

On Tue, 2021-12-07 at 17:53 +0000, Ross Burton wrote:

On Tue, 7 Dec 2021 at 17:15, Konrad Weihmann <kweihmann@...> wrote:

TBF

the correct fix would be

magic.bbclass
---
DEPENDS:append = " magic-dependency"
---

but unfortunately sometimes this is out of our control (as we don't want
to have bbclassappends for totally valid reasons)

Thoughts?

Personally, I'd say that's the correct fix, and any class that
DEPENDS= is just broken. Recipes should be able to do DEPENDS= because
that's convenient, and classes should use DEPENDS:append.

This is complicated by the issue that such appends are near impossible to
override, so you end up with the conditional bits in autotools/base.bbclass
adding variables to set to stop the behaviour. Classes should be a starting
point for things, not a hard requirement the recipe can't override.

If the goal is to let the recipe undo changes made by a .bbclass then
one easy solution is indirection. The class can use:

MAGIC_DEPENDS ?= "foo"
DEPENDS:append = " ${MAGIC_DEPENDS}"

Recipes can then override MAGIC_DEPENDS as required.

That does still feel like we're admitting our syntax is broken though :(

I actually much prefer += in recipes for that reason but as you say, people like
to use = and then the problem continues. This kind of issue is one of the things
we really need to solve as a project and is probably the most pressing syntax
problem. See the PACKAGECONFIG discussion/dilemma too.

I've seen the discussion. No real explanation of what the dilemma is though...

By that you mean I didn't expand on the other thread? Sadly I haven't had the
time, no. I didn't prioritise it as you made it clear you don't intend to send
patches to OE again. You have given a lot of good feedback on changes and have a
lot of good knowledge so that is a shame btw.

Things have been discussed in the past, I doubt I can dig out a precise pointer
to those discussions unfortunately as I'm struggling to find anything (I did
spend a while trying). I can try to summarise how I've seen the different sides
to this presented.

It basically comes down to users expecting to be able to do several different
things and different syntax works better for different use cases.

In general a user may want to a) change a single item in a config or b) override
the config entirely. They may want to do it for the target case only, or for
both target and native. They may want to do it from their local.conf (with a pn-
override?), from a .bbappend, or also from a distro configuration. It is also
complicated where these things may stack and the user may or may not need to
change a change to the PACKAGECONFIG.

Again, going from memory, depending on which of those things a user wants to do,
a ??=, ?=, = on the original PACKAGECONFIG may be more or less helpful.

I can try and work through each of the scenarios and write down which of the
operators makes most sense in each case and it is probably such an analysis we
need. Usually most people believe their favourite use case is the only one
anyone could ever want and is therefore the right one though :/. I struggle to
do work like this when patches aren't merging, we need milestone builds and the
autobuilder is showing breakage.

Cheers,

Richard