Fix rustfmt with remote exec

Author: dzbarsky

rs/experimental/toolchains/declare_rustfmt_toolchains.bzl

@@ -37,7 +37,7 @@ def declare_rustfmt_toolchains(
             name = rustfmt_toolchain_name,
             rustfmt = "{}rustfmt_bin".format(rustfmt_repo_label),
             rustc = "{}rustc".format(rustc_repo_label),
-            rustc_lib = "{}rustc_lib".format(rustc_repo_label),
+            rustc_lib = "{}rustc_lib".format(rustfmt_repo_label),
             visibility = ["//visibility:public"],
             tags = ["rust_version={}".format(version)],
         )

rs/private/rustfmt_repository.bzl

@@ -1,11 +1,25 @@
-load("@rules_rust//rust/private:repository_utils.bzl", "BUILD_for_rustfmt")
 load("@rules_rust//rust/platform:triple.bzl", "triple")
+load("@rules_rust//rust/private:repository_utils.bzl", "BUILD_for_rustfmt")
 load(":rust_repository_utils.bzl", "download_and_extract", "RUST_REPOSITORY_COMMON_ATTR")
 
+_RUSTFMT_LIB_FILEGROUP_TEMPLATE = """
+filegroup(
+    name = "rustc_lib",
+    srcs = ["lib", {upstream_rustc_lib}],
+    visibility = ["//visibility:public"],
+)
+"""
+
 def _rustfmt_repository_impl(rctx):
     exec_triple = triple(rctx.attr.triple)
     download_and_extract(rctx, "rustfmt", "rustfmt-preview", exec_triple)
-    rctx.file("BUILD.bazel", BUILD_for_rustfmt(exec_triple))
+
+    rctx.file(
+        "BUILD.bazel",
+        BUILD_for_rustfmt(exec_triple) + _RUSTFMT_LIB_FILEGROUP_TEMPLATE.format(
+            upstream_rustc_lib = repr(str(rctx.attr.rustc_repo_build_file.same_package_label("rustc_lib"))),
+        ),
+    )
 
     rustc_repo_root = rctx.path(rctx.attr.rustc_repo_build_file).dirname
     rctx.symlink(rustc_repo_root.get_child("lib"), "lib")

test/MODULE.bazel

@@ -51,6 +51,9 @@ local_path_override(
     path = "..",
 )
 
+rules_rust = use_extension("@rules_rs//rs/experimental:rules_rust.bzl", "rules_rust")
+use_repo(rules_rust, "rules_rust")
+
 toolchains = use_extension("@rules_rs//rs/experimental/toolchains:module_extension.bzl", "toolchains")
 toolchains.toolchain(
     edition = "2024",

test/workspace_path_dependency/BUILD.bazel

@@ -1,4 +1,5 @@
 load("@rules_rs//rs:rust_binary.bzl", "rust_binary")
+load("@rules_rust//rust:defs.bzl", "rust_clippy", "rustfmt_test")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -8,3 +9,13 @@ rust_binary(
     edition = "2024",
     deps = ["@workspace_path_dependency//:itoa"],
 )
+
+rustfmt_test(
+    name = "workspace_path_demo_rustfmt_test",
+    targets = [":workspace_path_demo"],
+)
+
+rust_clippy(
+    name = "workspace_path_demo_clippy_test",
+    deps = [":workspace_path_demo"],
+)