Add _experimental_toolchain_generated_sysroot attr

Author: Vinh Tran

.bazelci/presubmit.yml

@@ -92,8 +92,10 @@ tasks:
     test_targets: *default_linux_targets
     build_flags:
       - "--compilation_mode=opt"
+      - "--@rules_rust//rust/settings:experimental_toolchain_generated_sysroot=True"
     test_flags:
       - "--compilation_mode=opt"
+      - "--@rules_rust//rust/settings:experimental_toolchain_generated_sysroot=True"
   macos_opt:
     name: Opt Mode
     platform: macos

rust/private/rust.bzl

@@ -635,7 +635,7 @@ _common_attrs = {
         default = Label("//:experimental_per_crate_rustc_flag"),
     ),
     "_experimental_toolchain_generated_sysroot": attr.label(
-        default = Label("//rust/settings:experimental_toolchain_generated_sysroot"),
+        default = Label("@rules_rust//rust/settings:experimental_toolchain_generated_sysroot"),
     ),
     "_process_wrapper": attr.label(
         doc = "A process wrapper for running rustc on all platforms.",

rust/private/rustc.bzl

@@ -967,8 +967,10 @@ def construct_arguments(
         rustc_flags.add(linker_script, format = "--codegen=link-arg=-T%s")
 
     if sandboxed:
-        rustc_flags.add("--sysroot", toolchain.sysroot)
-    elif hasattr(ctx.attr, "_experimental_toolchain_generated_sysroot") and getattr(ctx.attr, "_experimental_toolchain_generated_sysroot") == True:
+        if hasattr(ctx.attr, "_experimental_toolchain_generated_sysroot"):
+            if ctx.attr._experimental_toolchain_generated_sysroot[BuildSettingInfo].value == True:
+                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)

rust/private/rustdoc.bzl

@@ -126,7 +126,6 @@ def rustdoc_compile_action(
         rustdoc = True,
         force_depend_on_objects = is_test,
         skip_expanding_rustc_env = True,
-        is_test = True,
         # rustdoc tests compile tests outside of the sandbox
         sandboxed = not is_test,
     )

rust/settings/BUILD.bazel

@@ -67,5 +67,5 @@ bzl_library(
 # 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,
+    build_setting_default = True,
 )

rust/toolchain.bzl

@@ -797,6 +797,13 @@ rust_toolchain = rule(
                 "This flag is only relevant when used together with --@rules_rust//rust/settings:experimental_use_global_allocator."
             ),
         ),
+        "_experimental_toolchain_generated_sysroot": attr.label(
+            default = Label("//rust/settings:experimental_toolchain_generated_sysroot"),
+            doc = (
+                "Label to a boolean build setting that lets the rule knows wheter to set --sysroot to rustc" +
+                "This flag is only relevant when used together with --@rules_rust//rust/settings:experimental_toolchain_generated_sysroot."
+            ),
+        ),
         "_no_std": attr.label(
             default = Label("//:no_std"),
         ),