service reflection: include transitive closure for a file

[jhump]

The Java implementation of the reflection service includes the entire transitive closure for a request file, in toplogical order such that a file's dependencies always appear after the file (so the requested file is first, with all of its dependencies after it).

However, the Go implementation only ever includes a single file and never includes its dependencies. It would be nice to also include the transitive closure (at least if a given file has never been sent) so that clients have a better chance of trying to link files even if the import name differs from the descriptor name. This is basically the same problem as golang/protobuf#567, except for downloading descriptors (vs. just querying the set of linked-in/registered descriptors).

Admittedly, having the set of transitive dependencies will still be error-prone if the names mismatch. The client could attempt to reconcile unlinkable descriptors by trying to match dependencies based only on the base name of the file and not its relative path. Or the set of descriptors could be provided in a well-specified order, that allows clients to compute the index for a given import and link it without relying on the name (which may not match).

For more context, see this: grpc/grpc#19832

[ejona86]

https://github.com/grpc/grpc/blob/master/doc/server-reflection.md specifies:

Any given request must either result in an error code or an answer, usually in the form of a series of FileDescriptorProtos with the requested file itself and all previously unsent transitive imports of that file.

So it appears this may be a bug instead of a feature request.

[stale]

This issue is labeled as requiring an update from the reporter, and no update has been received after 7 days. If no update is provided in the next 7 days, this issue will be automatically closed.

[jhump]

@dfawley, do you know what label that the stale bot is talking about? AFAICT, this is not waiting on any updates from me.

[dfawley]

stale bot is broken (I think just for labels with spaces): probot/stale#207