Automated rollback of commit fe7c4f94223ad2e6190102fbe3473ce3be19ec48.

PiperOrigin-RevId: 538128679

rust/BUILD

diff --git a/rust/BUILD b/rust/BUILD
index af69c57..e38f564 100644
--- a/rust/BUILD
+++ b/rust/BUILD
@@ -1,6 +1,6 @@
 # Protobuf Rust runtime packages.
 
-load("@rules_rust//rust:defs.bzl", "rust_library")
+load("@rules_rust//rust:defs.bzl", "rust_library", "rust_test")
 load("@bazel_skylib//rules:common_settings.bzl", "string_flag")
 
 load("@rules_proto//proto:defs.bzl", "proto_lang_toolchain")
@@ -30,22 +30,68 @@
         "//conditions:default": ["--cfg=cpp_kernel"],
     }),
     deps = select({
-        ":use_upb_kernel": ["//rust/upb_kernel:upb"],
-        "//conditions:default": ["//rust/cpp_kernel:cpp"],
+        ":use_upb_kernel": [":protobuf_upb"],
+        "//conditions:default": [":protobuf_cpp"],
     }),
 )
 
+# Represents Rust Protobuf runtime using the upb kernel.
+#
+# `rust_upb_proto_library` implicitly depends on this target. This target cannot depend on
+# `:rust_proto_library_kernel` build setting; it has to be fully functional under any value of that
+# setting.
+#
+# `shared.rs` contains kernel-agnostic logic and simple kernel-specific logic controlled by
+# `#[cfg(...)]` attributes. That forces us to compile this file twice, once for each kernel. As a
+# result this file is declared in both `:protobuf_upb` and `:protobuf_cpp`. This is in principle
+# identical to how we compile regular Rust source files twice (once for production, and once for
+# unittesting).
 rust_library(
-    name = "common",
-    srcs = ["common.rs"],
-    visibility = ["//rust:__subpackages__"],
+    name = "protobuf_upb",
+    srcs = ["shared.rs"],
+    rustc_flags = ["--cfg=upb_kernel"],
+    deps = ["//rust/upb_kernel:upb"],
+)
+
+rust_test(
+    name = "protobuf_upb_test",
+    crate = ":protobuf_upb",
+    rustc_flags = ["--cfg=upb_kernel"],
+    tags = [
+        # TODO(b/270274576): Enable testing on arm once we have a Rust Arm toolchain.
+        "not_build:arm",
+    ],
+)
+
+# Represents Rust Protobuf runtime using the cpp kernel.
+#
+# `rust_cpp_proto_library` implicitly depends on this target. This target cannot depend on
+# `:rust_proto_library_kernel` build setting; it has to be fully functional under any value of that
+# setting.
+#
+# See the comment for `:protobuf` for discussion of `shared.rs` file.
+rust_library(
+    name = "protobuf_cpp",
+    srcs = ["shared.rs"],
+    rustc_flags = ["--cfg=cpp_kernel"],
+    deps = ["//rust/cpp_kernel:cpp"],
+)
+
+rust_test(
+    name = "protobuf_cpp_test",
+    crate = ":protobuf_cpp",
+    rustc_flags = ["--cfg=cpp_kernel"],
+    tags = [
+        # TODO(b/270274576): Enable testing on arm once we have a Rust Arm toolchain.
+        "not_build:arm",
+    ],
 )
 
 proto_lang_toolchain(
     name = "proto_rust_upb_toolchain",
     command_line = "--rust_out=experimental-codegen=enabled,kernel=upb:$(OUT)",
     progress_message = "Generating Rust proto_library %{label}",
-    runtime = "//rust/upb_kernel:upb",
+    runtime = ":protobuf_upb",
     visibility = ["//visibility:public"],
 )
 
@@ -53,7 +99,7 @@
     name = "proto_rust_cpp_toolchain",
     command_line = "--rust_out=experimental-codegen=enabled,kernel=cpp:$(OUT)",
     progress_message = "Generating Rust proto_library %{label}",
-    runtime = "//rust/cpp_kernel:cpp",
+    runtime = ":protobuf_cpp",
     visibility = ["//visibility:public"],
 )