Add support for Bzlmod (fixes #515).

Specifically, this allows P4Runtime users to use Bzlmod.
I am not yet enabling Blzmod for P4Runtime itself. I plan to do so in a follow up PR.

Signed-off-by: Steffen Smolka <[email protected]>

bazel/example/using-bzlmod/.bazelrc

@@ -0,0 +1,6 @@
+# Use Bzlmod instead of WORKSPACE.
+common --enable_bzlmod
+common --noenable_workspace
+
+# C++14 required for recent gRPC versions
+build --cxxopt='-std=c++14'

bazel/example/using-bzlmod/MODULE.bazel

@@ -0,0 +1,24 @@
+bazel_dep(
+    name = "p4runtime",
+    repo_name = "com_github_p4lang_p4runtime",
+)
+
+# In your own project, you will likely want to use `http_archive` instead
+# of `local_repository` to load p4runtime.
+local_path_override(
+    module_name = "p4runtime",
+    path = "../../../proto",
+)
+
+# git_override(
+#     module_name = "p4runtime",
+#     strip_prefix = "p4runtime-1.4.1/proto",
+#     urls = ["https://github.com/p4lang/p4runtime/archive/v1.4.1.tar.gz"],
+#     # sha256 = "<insert hash value here>",
+# )
+
+bazel_dep(
+    name = "protobuf",
+    version = "29.1",
+    repo_name = "com_google_protobuf",
+)

bazel/example/using-workspace/BUILD.bazel

@@ -0,0 +1,8 @@
+cc_binary(
+  name = "hello_p4runtime",
+  srcs = ["hello_p4runtime.cc"],
+  deps = [
+    "@com_github_p4lang_p4runtime//:p4info_cc_proto",
+    "@com_google_protobuf//:protobuf",
+  ]
+)

bazel/example/WORKSPACE.bazel → bazel/example/using-workspace/WORKSPACE.bazel

@@ -5,7 +5,7 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 # of `local_repository` to load p4runtime.
 local_repository(
     name = "com_github_p4lang_p4runtime",
-    path = "../../proto",
+    path = "../../../proto",
 )
 # http_archive(
 #     name = "com_github_p4lang_p4runtime",

bazel/example/using-workspace/hello_p4runtime.cc

@@ -0,0 +1,21 @@
+#include <iostream>
+
+#include "google/protobuf/text_format.h"
+#include "p4/config/v1/p4info.pb.h"
+
+using ::google::protobuf::TextFormat;
+using ::p4::config::v1::P4Info;
+
+int main() {
+  P4Info p4info;
+  TextFormat::ParseFromString(R"PROTO(
+                                  tables {
+                                    preamble {
+                                      id: 10
+                                      name: "Hello, P4Runtime!"
+                                    }
+                                  }
+                                )PROTO", &p4info);
+  p4info.mutable_tables()->at(0).mutable_preamble()->set_id(42);
+  std::cout << p4info.DebugString();
+}

proto/MODULE.bazel

@@ -0,0 +1,34 @@
+module(
+    name = "p4runtime",
+    repo_name = "com_github_p4lang_p4runtime",
+)
+
+bazel_dep(name = "bazel_skylib", version = "1.7.1")
+bazel_dep(
+    name = "googleapis",
+    version = "0.0.0-20240819-fe8ba054a",
+    repo_name = "com_google_googleapis",
+)
+
+switched_rules = use_extension("@com_google_googleapis//:extensions.bzl", "switched_rules")
+switched_rules.use_languages(
+    cc = True,
+    go = True,
+    grpc = True,
+    python = True,
+)
+use_repo(switched_rules, "com_google_googleapis_imports")
+
+bazel_dep(name = "grpc", version = "1.68.0", repo_name = "com_github_grpc_grpc")
+bazel_dep(
+    name = "protobuf",
+    version = "29.1",
+    repo_name = "com_google_protobuf",
+)
+bazel_dep(name = "rules_license", version = "1.0.0")
+bazel_dep(name = "rules_proto", version = "7.0.2")
+bazel_dep(
+    name = "rules_go",
+    version = "0.50.1",
+    repo_name = "io_bazel_rules_go",
+)

proto/WORKSPACE.bzlmod

@@ -0,0 +1,5 @@
+# https://bazel.build/external/migration#workspace.bzlmod
+#
+# This file is intentionally empty. When bzlmod is enabled and this
+# file exists, the contents of WORKSPACE.bazel is ignored. This prevents
+# bzlmod builds from unintentionally depending on the WORKSPACE.bazel file.