Re: Variable key replaces original warnings

[Olof Johansson <olof.johansson@axis.com>]

Excerpts from Richard Purdie's message of 2015-07-31 11:54:02 +0200:
> On Thu, 2015-07-30 at 17:03 +0200, Olof Johansson wrote:
> > I made a unit test that should demonstrate the problem (I think), and it fails
> > because of the warnings:
> > 
> > diff --git a/bitbake/lib/bb/tests/data.py b/bitbake/lib/bb/tests/data.py
> > index e9aab57..e7716cc 100644
> > --- a/bitbake/lib/bb/tests/data.py
> > +++ b/bitbake/lib/bb/tests/data.py
> > @@ -386,6 +386,15 @@ class TestKeyExpansion(unittest.TestCase):
> >              self.assertTrue(logContains("Variable key VAL_${FOO} (A) replaces original key VAL_foo (B)", logs))
> >          self.assertEqual(self.d.getVar("VAL_foo", True), "A")
> >  
> > +    def test_append(self):
> > +        self.d.setVar("TEST_${BAR}", "Bar")
> > +        self.d.setVar("TEST_${FOO}_append", "Foo")
> > +        with LogRecord() as logs:
> > +            bb.data.expandKeys(self.d)
> > +            self.assertFalse(logContains("Variable key TEST_${FOO} (Foo) replaces original key TEST_foo (Bar)", logs))
> > +        self.assertEqual(self.d.getVar("TEST_${FOO}", True), "BarFoo")
> > 
> > 
> > If you have any ideas on what this issue can be or how to fix it, please
> > let me know :)
> 
> The data store changes recently caused a number of these to appear. The
> issue has always been there, as has this warning, the new datastore code
> just exposes it a bit more consistently than previously.
> 
> The reason we do this is that users with conflicting (different values)
> of the same variable name usually have a metadata issue they're unaware
> of.

Thanks. But that's not the case for us. Why is this relevant for _append
operations? The exanded variable does get the expected value (which can
be verified by uncommenting the assertFalse for the log in my unit
test).

> The fix is to ensure you only set a variable in one canonical way.

Why? For our purpose that's not ideal. We want to be able to create a
user with a common definition from a set of packages. It's not
necessarily the recipes' ${PN} package that will create such a user.

-- 
olof johansson