packs do not check for missing compression parents

I'll give this a shot.

for efficiency I suggest that this be done as:
fetch all the texts - _copy_nodes_graph
after that, use nodes to generate a set of referenced texts
text_refs = set()
text_keys = set()
        for index, key, value, references in nodes:
            if references[1]:
                text_refs.update(references[1])
            text_keys.add(key)

Then filter that by the keys copied
external_refs = text_refs - text_keys

Now look up external_refs in self._pack_collection.text_index.combined_index
found_items = list(self._pack_collection.text_index.combined_index.iter_entries(external_refs))
if len(found_items) != len(external_refs):
    identify the missing ones here.

-Rob

I don't see mail from John saying he finished this, so I'll try to pick it up.

https://code.edge.launchpad.net/~jameinel/bzr/fetch-check-parents-165290

ok, john seems to have added a plausible test for this (test_fetch_missing_basis_text), and to have code in pack_repo along the lines Robert suggests. However, the test does not actually observe the expected error when pulling into a repository that is missing texts it ought to have.

In the relevant test we're called on an InterPackRepo, and into its .fetch method. This does seem to call Packer.pack(), which should run the checks...

Strangely enough inside the fetch we have self.source._pack_collection.all_packs() returning None. However, there are two packs in the source directory, and they are named correctly by the pack-names file, and returned from the _pack_collection.names() method. But:

(Pdb) spc.get_pack_by_name('b93e1621bbfcd744e128a46c27058d79')
*** AttributeError: 'ExistingPack' object has no attribute 'transport'

ah, the problem seems to be that the ExistingPack is unprintable because its str method tries to use a missing attribute; so this is annoying but not a big problem.

to be continued...

ok, i think this is not far off, but I won't have time to finish it and have it reviewed for our deadline.

It has been finished in the attached branch.