Set --sysroot in construct_arguments

Author: Vinh Tran

rust/private/rust.bzl

@@ -634,6 +634,9 @@ _common_attrs = {
     "_per_crate_rustc_flag": attr.label(
         default = Label("//:experimental_per_crate_rustc_flag"),
     ),
+    "_experimental_toolchain_generated_sysroot": attr.label(
+        default = Label("//rust/settings:experimental_toolchain_generated_sysroot"),
+    ),
     "_process_wrapper": attr.label(
         doc = "A process wrapper for running rustc on all platforms.",
         default = Label("//util/process_wrapper"),

rust/private/rustc.bzl

@@ -788,7 +788,8 @@ def construct_arguments(
         use_json_output = False,
         build_metadata = False,
         force_depend_on_objects = False,
-        skip_expanding_rustc_env = False):
+        skip_expanding_rustc_env = False,
+        sandboxed_sysroot = True):
     """Builds an Args object containing common rustc flags
 
     Args:
@@ -965,6 +966,11 @@ def construct_arguments(
     if linker_script:
         rustc_flags.add(linker_script, format = "--codegen=link-arg=-T%s")
 
+    if sandboxed_sysroot:
+        rustc_flags.add("--sysroot", toolchain.sysroot)
+    else:
+        rustc_flags.add(toolchain.sysroot_short_path, format = "--sysroot=${{pwd}}/%s")
+
     # Tell Rustc where to find the standard library (or libcore)
     rustc_flags.add_all(toolchain.rust_std_paths, before_each = "-L", format_each = "%s")
     rustc_flags.add_all(rust_flags)
@@ -1264,22 +1270,14 @@ def rustc_compile_action(
             dsym_folder = ctx.actions.declare_directory(crate_info.output.basename + ".dSYM", sibling = crate_info.output)
             action_outputs.append(dsym_folder)
 
-    rustc_sysroot_arg = ctx.actions.args()
-    rustc_sysroot_arg.add("--sysroot", toolchain.sysroot)
-
     if ctx.executable._process_wrapper:
         # Run as normal
         ctx.actions.run(
             executable = ctx.executable._process_wrapper,
             inputs = compile_inputs,
             outputs = action_outputs,
             env = env,
-            arguments = [
-                args.process_wrapper_flags,
-                args.rustc_path,
-                rustc_sysroot_arg,
-                args.rustc_flags,
-            ],
+            arguments = args.all,
             mnemonic = "Rustc",
             progress_message = "Compiling Rust {} {}{} ({} files)".format(
                 crate_info.type,
@@ -1295,12 +1293,7 @@ def rustc_compile_action(
                 inputs = compile_inputs,
                 outputs = [build_metadata],
                 env = env,
-                arguments = [
-                    args_metadata.process_wrapper_flags,
-                    args_metadata.rustc_path,
-                    rustc_sysroot_arg,
-                    args_metadata.rustc_flags,
-                ],
+                arguments = args_metadata.all,
                 mnemonic = "RustcMetadata",
                 progress_message = "Compiling Rust metadata {} {}{} ({} files)".format(
                     crate_info.type,
@@ -1319,7 +1312,7 @@ def rustc_compile_action(
             inputs = compile_inputs,
             outputs = action_outputs,
             env = env,
-            arguments = [args.rustc_path, rustc_sysroot_arg, args.rustc_flags],
+            arguments = [args.rustc_path, args.rustc_flags],
             mnemonic = "Rustc",
             progress_message = "Compiling Rust (without process_wrapper) {} {}{} ({} files)".format(
                 crate_info.type,

rust/private/rustdoc.bzl

@@ -126,6 +126,8 @@ def rustdoc_compile_action(
         rustdoc = True,
         force_depend_on_objects = is_test,
         skip_expanding_rustc_env = True,
+        is_test = True,
+        sandboxed_sysroot = not is_test,
     )
 
     # Because rustdoc tests compile tests outside of the sandbox, the sysroot
@@ -137,10 +139,6 @@ def rustdoc_compile_action(
         if "OUT_DIR" in env:
             env.update({"OUT_DIR": "${{pwd}}/{}".format(build_info.out_dir.short_path)})
 
-        # `rustdoc` does not support the SYSROOT environment variable. To account
-        # for this, the flag must be explicitly passed to the `rustdoc` binary.
-        args.rustc_flags.add(toolchain.sysroot_short_path, format = "--sysroot=${{pwd}}/%s")
-
     return struct(
         executable = ctx.executable._process_wrapper,
         inputs = depset([crate_info.output], transitive = [compile_inputs]),

rust/settings/BUILD.bazel

@@ -63,3 +63,9 @@ bzl_library(
     name = "bzl_lib",
     srcs = glob(["**/*.bzl"]),
 )
+
+# A flag to set rustc --sysroot flag to the sysroot generated by rust_toolchain
+bool_flag(
+    name = "experimental_toolchain_generated_sysroot",
+    build_setting_default = False,
+)