what to put in WORKSPACE and/or BUILD files to enable the cc_proto_library rule?

[JI Ioannidis]

What is the sequence of magic incantations to create a cc_proto_library rule? I have tried copying protobuf.bzl from the protobuf repo to the root of my workspace, as well as some (at least a year old) .bzl files referenced in this group, to no avail.

My end goal is to have a BUILD file such as 

$ cat protoa/BUILD  
cc_proto_library(
 name = "alice",
 srcs = ["alice.proto"],
)

then type 

$ bazel build //protoa:alice

and have it create the right .pb.h and .pb.cc files

FWIW, I have already installed bazel at sha 42d8290 (compiled, bazel binary copied to ~/bin/) and built and installed protobuf at sha b99577c. 

Thanks!

/ji

[Paul Johnston]

1. During the loading phase, bring the google/protobuf into your WORKSPACE so you can refer to it as @com_github_google_protobuf later.  The bazel convention is to have fully qualified names, flattening special characters to underscore.

git_repository(

  name = "com_github_google_protobuf",

  remote = "https://github.com/google/protobuf.git",

  tag = "v3.0.0",

)

2. During the analysis phase, load the function in your BUILD file by referring to the skylark bzl filename.  

    As the protobuf repo has a BUILD file in the root (which defines it as a "package"), you need to refer to the 

    bzl relative to the package name.  That's why you need the colon. 

# You can also alias the function to whatever you want with 'foo = "cc_proto_library"'

load("@com_github_google_protobuf//:protobuf.bzl", "cc_proto_library")

# These are called "target pattern operators" IIRC

@ = names an external dependency that is loaded in WORKSPACE.

// = relative to the workspace root

: relative to package

3. Call it

cc_proto_library( 
 name = "alice", 
 srcs = ["alice.proto"], 
)

But then, where did the files go?  If it worked, they should be in $(bazel info bazel-genfiles)/protoa/alice.pb.h

I've been working on a set of rules for protobuf +/- gRPC at https://github.com/pubref/rules_protobuf.  Perhaps it will be of use to you.