prototxt.bzl

load("@rules_python//python:defs.bzl", "py_library")

_PROTOTXT_COMMAND = """
cat <<EOF >>{out}
# Autogenerated by bazel. DO NOT EDIT.

from google.protobuf import text_format
from {pkg} import {message}

text = \"\"\"
EOF
cat {src} >> {out}
cat <<EOF >>{out}
\"\"\"

{varname} = text_format.Parse(text, {message}())
EOF
"""

def _prototxt_py(ctx):
    # Source .prototxt file
    src = ctx.files.src[0]

    # Output python file
    out_file = ctx.outputs.out

    command = _PROTOTXT_COMMAND.format(
        src = src.path,
        out = out_file.path,
        pkg = ctx.attr.pkg,
        varname = ctx.attr.varname,
        message = ctx.attr.message,
    )

    ctx.actions.run_shell(
        outputs = [out_file],
        command = command,
        inputs = [src],
    )

genprototxt_py = rule(
    implementation = _prototxt_py,
    attrs = {
        "src": attr.label(
            doc = "The prototxt source file.",
            mandatory = True,
            allow_single_file = True,
        ),
        "out": attr.output(
            doc = "Where to write the python file.",
            mandatory = True,
        ),
        "pkg": attr.string(
            doc = "Python path to protobuf library.",
            mandatory = True,
        ),
        "varname": attr.string(
            doc = "Variable name.",
            mandatory = True,
        ),
        "message": attr.string(
            doc = "Protocol buffers message name.",
            mandatory = True,
        ),
    },
)

def prototxt_py(*, name, src, pkg, varname, message, **kwargs):
    gen_name = name + "_py"
    gen_out = name + ".py"

    genprototxt_py(
        name = gen_name,
        src = src,
        out = gen_out,
        pkg = pkg,
        varname = varname,
        message = message,
    )

    py_library(
        name = name,
        srcs = [gen_out],
        **kwargs
    )