google.protobuf for python 3

[smessmer]

This allows usage of the google.protobuf type stubs from python 3 code.

[JelleZijlstra]

Thanks for the PR! What have you done to test that these stubs work right in Python 3?

[smessmer]

We're using these in one of our projects, where they work fine. However, coverage is very likely incomplete.

[JelleZijlstra]

Thanks. I noticed there are a ton of functions like protobuf/wrappers_pb2.pyi: def FromString(cls, s: str) -> FloatValue: .... Do those really take str, not bytes in Python 3? I don't have an easy way to check.

[smessmer]

They probably take bytes, but I don't have an easy way to check either. I did change a few call sites from str to bytes where we used them and I know they're actually meant to be bytes.

[JelleZijlstra]

Is it reasonable to assume that all FromString methods take the same type?

[smessmer]

I'm unsure. Somebody implemented MergeFromString and ParseFromString in Message to take type Any.

[gvanrossum]

PS. See also #2157.

[JelleZijlstra]

This has some conflicts now.

[nipunn1313]

All FromString methods do in fact take bytes. They take in a serialized input.
FromString is a bit of a misnomer in python3, but the naming was designed for python2.

I believe that google.protobuf uses the same code for both python2 and python3, so as long as we use bytes and Text, we shouldn't have (in theory) any typing issues.

That being said, unexpected things do occur. I'm not sure there's a worthwhile way for us to derisk all of these up front.

In #2174 - I made a similar diff which replaced all instances of str -> bytes.

[JelleZijlstra]

I merged #2174 instead.