goyang: Cannot replace node with deviate/augment combo

We have a YANG module that we implement (ietf-routing-policy), but there are some changes that we’ve made. In order to maintain a separation between the IETF module and our modifications, instead of directly modifying the IETF module, we have removed unsupported nodes using deviations, and added new nodes by augmenting from a separate module.

The problem occurs when we remove an unsupported node and then try to replace it with a different node of the same name. The new node comes from a different module and therefore has a different prefix, but Entry.Dir only cares about unprefixed names. So when the deviations are applied, it wipes out the new node.

I’m aware that prefix handling is incomplete (https://github.com/openconfig/goyang/issues/5) in goyang, and that we cannot change the way Entry.Dir works without serious consequences. I would like to propose a workaround, in which we maintain a secondary map Entry.PrefixedDir which acts exactly like Entry.Dir except that its map keys are qualified with a prefix.

I have a branch in which I’ve made these changes, but I wanted to get feedback before submitting a PR.