Resolution of imported names

[j6carey]

Name resolution in compile-proto-file deviates from that of protoc and from this portion of the specification:

https://developers.google.com/protocol-buffers/docs/proto3#packages_and_name_resolution

Specifically, compile-proto-file allows unqualified lookup of imported names, which seems to be nonstandard, but fails to find qualified names unless they start at the top package component. It should look up both qualified and unqualified names relative to the current package, its parent package, and so forth, on up to the root--except for names that start with a period, which are always relative to the root (that is, absolute).

Consider the following two test inputs:

$ cat test1.proto 
syntax = "proto3";
package test.sub1;
message Message1 {}

$ cat test2.proto 
syntax = "proto3";
package test.sub2;
import "test1.proto";
message Message2 { sub1.Message1 sub = 1; }

protoc accepts test2.proto, but rejects it if we remove the sub1. qualification from the reference to Message1.

By contrast, compile-proto-file rejects test2.proto:

compile-proto-file --proto test2.proto --out t
Error: failed to compile "test2.proto":

NoSuchType (Dots (Path {components = "sub1" :| ["Message1"]}))

But if we remove the sub1 qualification then then compile-proto-file succeeds--even though protoc would fail in that case.

If we expand qualification to test.sub1.Message1 or the absolute path .test.sub1.Message1 then both compile-proto-file and protoc accept the input.