Python API - nested pretty printers MI implications

[Andrew Oakley <andrew@ado.is-a-geek.net>]

I've got a patch to allow the Python pretty printer children iterators
to return more pretty printers so they can create "phony groups" a bit
like this:

class outer_pretty_printer:
	class inner_pretty_printer:
		def __init__(self, ...):
			...

		def to_string(self):
			...

		def children(self):
			...

	def __init__(self, val):
		...

	def to_string(self):
		...

	def children(self):
		yield ("normal variable", "some value")
		yield ("phony group 1", inner_pretty_printer(...))
		yield ("phony group 2", inner_pretty_printer(...))

This seems to work well but I'm not quite sure how to handle the for MI.

As far as I can tell I need to create "fake" varobj structures with no
underlying value or type (because I don't have one).  This appears to
already happen and is tested for with CPLUS_FAKE_CHILD, but I'm not
quite sure what that is for.  Does this seem like a reasonable thing to
do (after searching around for CPLUS_FAKE_CHILD)?

My other worry is varobj invalidation and update.  Am I correct in
thinking that updates can only happen from a "root" varobj?  If so it
should be possible to reconstruct the "fake" varobj structures in
varobj_update (I don't think it will be straightforward though).

Am I correct in assuming you would want MI to work before accepting
patches?

-- 
Andrew Oakley