Remove protoc from proto_lang_toolchain rule

The protoc should be provided with a new proto_toolchain rule.

Issue: bazelbuild/rules_proto#179

RELNOTES[INC]: proto_compiler attribute removed from proto_lang_toolchain
(it was recently introduced, and there is no evidence of use)

PiperOrigin-RevId: 566937038
Change-Id: I7133be4d5cbcc816764c0ba35607329ea50d2406

src/main/starlark/builtins_bzl/common/exports.bzl

@@ -24,7 +24,7 @@ load("@_builtins//:common/objc/compilation_support.bzl", "compilation_support")
 load("@_builtins//:common/objc/linking_support.bzl", "linking_support")
 load("@_builtins//:common/proto/proto_common.bzl", "proto_common_do_not_use")
 load("@_builtins//:common/proto/proto_library.bzl", "proto_library")
-load("@_builtins//:common/proto/proto_lang_toolchain_wrapper.bzl", "proto_lang_toolchain")
+load("@_builtins//:common/proto/proto_lang_toolchain.bzl", "proto_lang_toolchain")
 load("@_builtins//:common/python/py_runtime_macro.bzl", "py_runtime")
 load("@_builtins//:common/python/providers.bzl", "PyInfo", "PyRuntimeInfo")
 load("@_builtins//:common/java/proto/java_lite_proto_library.bzl", "java_lite_proto_library")

src/main/starlark/builtins_bzl/common/proto/proto_lang_toolchain.bzl

@@ -31,9 +31,6 @@ def _rule_impl(ctx):
     if ctx.attr.plugin != None:
         plugin = ctx.attr.plugin[DefaultInfo].files_to_run
 
-    proto_compiler = getattr(ctx.attr, "proto_compiler", None)
-    proto_compiler = getattr(ctx.attr, "_proto_compiler", proto_compiler)
-
     return [
         DefaultInfo(
             files = depset(),
@@ -46,46 +43,37 @@ def _rule_impl(ctx):
             plugin = plugin,
             runtime = ctx.attr.runtime,
             provided_proto_sources = provided_proto_sources,
-            proto_compiler = proto_compiler.files_to_run,
+            proto_compiler = ctx.attr._proto_compiler.files_to_run,
             protoc_opts = ctx.fragments.proto.experimental_protoc_opts,
             progress_message = ctx.attr.progress_message,
             mnemonic = ctx.attr.mnemonic,
         ),
     ]
 
-def make_proto_lang_toolchain(custom_proto_compiler):
-    return rule(
-        _rule_impl,
-        attrs = dict(
-            {
-                "progress_message": attr.string(default = "Generating proto_library %{label}"),
-                "mnemonic": attr.string(default = "GenProto"),
-                "command_line": attr.string(mandatory = True),
-                "output_files": attr.string(values = ["single", "multiple", "legacy"], default = "legacy"),
-                "plugin_format_flag": attr.string(),
-                "plugin": attr.label(
-                    executable = True,
-                    cfg = "exec",
-                ),
-                "runtime": attr.label(),
-                "blacklisted_protos": attr.label_list(
-                    providers = [ProtoInfo],
-                ),
-            },
-            **({
-                "proto_compiler": attr.label(
-                    cfg = "exec",
-                    executable = True,
-                ),
-            } if custom_proto_compiler else {
-                "_proto_compiler": attr.label(
-                    cfg = "exec",
-                    executable = True,
-                    allow_files = True,
-                    default = configuration_field("proto", "proto_compiler"),
-                ),
-            })
-        ),
-        provides = [ProtoLangToolchainInfo],
-        fragments = ["proto"] + semantics.EXTRA_FRAGMENTS,
-    )
+proto_lang_toolchain = rule(
+    _rule_impl,
+    attrs =
+        {
+            "progress_message": attr.string(default = "Generating proto_library %{label}"),
+            "mnemonic": attr.string(default = "GenProto"),
+            "command_line": attr.string(mandatory = True),
+            "output_files": attr.string(values = ["single", "multiple", "legacy"], default = "legacy"),
+            "plugin_format_flag": attr.string(),
+            "plugin": attr.label(
+                executable = True,
+                cfg = "exec",
+            ),
+            "runtime": attr.label(),
+            "blacklisted_protos": attr.label_list(
+                providers = [ProtoInfo],
+            ),
+            "_proto_compiler": attr.label(
+                cfg = "exec",
+                executable = True,
+                allow_files = True,
+                default = configuration_field("proto", "proto_compiler"),
+            ),
+        },
+    provides = [ProtoLangToolchainInfo],
+    fragments = ["proto"],
+)

src/test/java/com/google/devtools/build/lib/rules/proto/ProtoLangToolchainTest.java

@@ -96,40 +96,6 @@ public void protoToolchain() throws Exception {
     validateProtoCompiler(toolchain, ProtoConstants.DEFAULT_PROTOC_LABEL);
   }
 
-  @Test
-  public void protoToolchain_setProtoCompiler() throws Exception {
-    scratch.file(
-        "third_party/x/BUILD",
-        "licenses(['unencumbered'])",
-        "cc_binary(name = 'plugin', srcs = ['plugin.cc'])",
-        "cc_library(name = 'runtime', srcs = ['runtime.cc'])",
-        "filegroup(name = 'descriptors', srcs = ['metadata.proto', 'descriptor.proto'])",
-        "filegroup(name = 'any', srcs = ['any.proto'])",
-        "proto_library(name = 'denied', srcs = [':descriptors', ':any'])",
-        "cc_binary(name = 'compiler')");
-
-    scratch.file(
-        "foo/BUILD",
-        TestConstants.LOAD_PROTO_LANG_TOOLCHAIN,
-        "licenses(['unencumbered'])",
-        "proto_lang_toolchain(",
-        "    name = 'toolchain',",
-        "    command_line = 'cmd-line:$(OUT)',",
-        "    plugin_format_flag = '--plugin=%s',",
-        "    plugin = '//third_party/x:plugin',",
-        "    runtime = '//third_party/x:runtime',",
-        "    progress_message = 'Progress Message %{label}',",
-        "    mnemonic = 'MyMnemonic',",
-        "    proto_compiler = '//third_party/x:compiler',",
-        ")");
-
-    ProtoLangToolchainProvider toolchain =
-        ProtoLangToolchainProvider.get(getConfiguredTarget("//foo:toolchain"));
-
-    validateProtoLangToolchain(toolchain);
-    validateProtoCompiler(toolchain, "//third_party/x:compiler");
-  }
-
   @Test
   public void protoToolchainBlacklistProtoLibraries() throws Exception {
     scratch.file(