tree 6d1d577b462f4e72388ce9c14c04b812013bb6c5
parent bac4cd44d425e0020f391d734b3940aaea60f3c8
author Damien Neil <dneil@google.com> 1557327169 -0700
committer Damien Neil <dneil@google.com> 1557336294 +0000

internal/{fileinit,impl}: minimal weak field support

Weak fields are an obsolete proto1 feature. They have been superseded
by extensions. However, some vestigial support for weak fields does
remain, mostly as Google-internal patches. (They aren't exciting;
extensions really do everything weak fields do in a cleaner and
more portable fashion.)

At the moment, the only visible impact of marking a field [weak=true]
is to exclude it from "internal/fileinit".FileBuilder.DependencyIndexes.
We want to preserve that behavior just in case we ever do add full weak
field support here.

Extend fileinit to look up message descriptors for weak fields in the
global registry. If the descriptor cannot be found, use a placeholder
instead.

Remove special-case handling of weak fields in the impl package. The
code generator doesn't do anything special for them, so they can be
treated as any other field.

Change-Id: Ifa2ee3d30d63680a0eeb59c66ebc9521f38fd660
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/175997
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>