Using the presence of the `*_pb2_grpc` module, as opposed to the absence
of the build script (`*_commands` module) is a problematic choice,
because even if a generated file is present, the test infrastructure may
want to regenerate it under a different environment (e.g. different
Python/proto package version). This will ensure the protos always get
recompiled if we have a `*_commands` module present, signaling we are in
a build environment, thereby making the process hermetic.
The previous packaging structure exhibited strange behavior of
slowness when trying to use pip to install grpcio-reflection
or grpcio-health-checking in a single line with grpcio-tools.
The root cause seems to be the complicated interaction between
pip and setuptools and the fact that we ship a single .tar.gz
"source" archive for `grpcio_reflection` and
`grpcio_health_checking` packages. `pip` tries to build this
"source" package, and our build process wants to generate
code for the `.proto` files in the package. However, we have
already processed the `.proto` files into `_pb2.py` files in
our artifact build process, and installing `grpcio_tools`
to get `grpcio_{reflection,health_checking}` seems excessive.
The behavior gets worse since `setuptools`, while building
the package from source, tries to fetch `grpcio_tools` from
source and build that too. This takes a while, since it
involves compiling a bunch of native code from `protobuf` and
`grpc` and requires a C compiler to boot.
This commit modifies the Python artifact for the two packages
so that they will not include the raw `.proto` files in the
distribution uploaded to PyPI, nor would they contain the
Python module that does the preprocessing code generation
from the respective .proto files. Instead, a specific code
path is taken when the generated `_pb2_grpc` Python module is
not present in the package to provide such functionality
when built from the gRPC git repository (and hence when built
from our CI infrastructure.)
To support magical internal build processes, the pb2 files need to be
split into pure-proto and gRPC parts. This performs that split and
further fixes bad module names in the test harness that interfered with
the intended test implementation.
An unfortunate side effect, due to limitations of protoc and holdover
behavior we must support in major version 1.x, is that trash files are
generated in split generation. This shouldn't be a problem in normal
protoc plugin use.
Mehrdad Afshari