bitbake: data.py: Add a warning when expandKeys overwrites an existing key

When two variables are defined as:

${var} = "bar"
foo = "foobar"

The value of 'foo' when ${var} == foo becomes indeterminate.  We
want to warn a user when this situation has been encountered so they
can take corrective actions.

In the above example usually foo == bar, unless multilibs are enabled.
Then ml-foo = "ml-foobar".

(Bitbake rev: 7c568132c54a21161de28907159f902462f1e2bb)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data.py

@@ -158,6 +158,11 @@ def expandKeys(alterdata, readdata = None):
 
     for key in todolist:
         ekey = todolist[key]
+        if ekey in keys(alterdata):
+            val = alterdata.getVar(key, 0)
+            newval = alterdata.getVar(ekey, 0)
+            if val is not None and newval is not None:
+                bb.warn("Variable key %s (%s) replaces original key %s (%s)." % (key, val, ekey, newval))
         alterdata.renameVar(key, ekey)
 
 def inheritFromOS(d, savedenv, permitted):