bitbake: event: Add event for deferred inherits

Now that deferred inherits are extension specific, we can pass this
list to an event, which our metadata can use to set class overrides
earlier (as an example).

There are limitations to this, the list of classes is unexpanded and
recursive classes are not visible. There isn't much that can be done
about this, the ones we are interested in would usually be visible
at the top level (such as class extensions).

(Bitbake rev: 205d461c05fc7b4a7c81039af3bc3fd71cbb982c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/event.py

@@ -431,6 +431,16 @@ class RecipeEvent(Event):
         self.fn = fn
         Event.__init__(self)
 
+class RecipePreDeferredInherits(RecipeEvent):
+    """
+    Called before deferred inherits are processed so code can snoop on class extensions for example
+    Limitations: It won't see inherits of inherited classes and the data is unexpanded
+    """
+    def __init__(self, fn, inherits):
+        self.fn = fn
+        self.inherits = inherits
+        Event.__init__(self)
+
 class RecipePreFinalise(RecipeEvent):
     """ Recipe Parsing Complete but not yet finalised"""
 

bitbake/lib/bb/parse/ast.py

@@ -471,6 +471,9 @@ def finalize(fn, d, variant = None):
         if d.getVar("_FAILPARSINGERRORHANDLED", False) == True:
             raise bb.BBHandledException()
 
+        inherits = [x[0] for x in (d.getVar('__BBDEFINHERITS', False) or [('',)])]
+        bb.event.fire(bb.event.RecipePreDeferredInherits(fn, inherits), d)
+
         while True:
             inherits = d.getVar('__BBDEFINHERITS', False) or []
             if not inherits: