Downloads rust-toolchain-aux.

DEPS

@@ -176,6 +176,11 @@ hooks = [
     "condition": 'checkout_mac and host_os != "mac" and checkout_dmg_tool',
     'action': ['build/mac/cross-compile/build-libdmg-hfsplus.py', 'third_party/libdmg-hfsplus']
   },
+  {
+    'name': 'download_rust_toolchain_aux',
+    'pattern': '.',
+    'action': ['python3', 'build/rust/download_rust_toolchain_aux.py']
+  },
 ]
 
 include_rules = [

build/commands/lib/config.js

@@ -254,6 +254,7 @@ const Config = function () {
   this.service_key_aichat = getEnvConfig(['service_key_aichat']) || ''
   this.braveIOSDeveloperOptionsCode = getEnvConfig(['brave_ios_developer_options_code']) || ''
   this.service_key_stt = getEnvConfig(['service_key_stt']) || ''
+  this.skip_download_rust_toolchain_aux = getEnvConfig(['skip_download_rust_toolchain_aux']) || false
 }
 
 Config.prototype.isReleaseBuild = function () {
@@ -1137,6 +1138,10 @@ Object.defineProperty(Config.prototype, 'defaultOptions', {
       env.VSCMD_SKIP_SENDTELEMETRY = '1'
     }
 
+    if (this.isCI && this.skip_download_rust_toolchain_aux) {
+      env.SKIP_DOWNLOAD_RUST_TOOLCHAIN_AUX = '1'
+    }
+
     // TeamCity displays only stderr on the "Build Problems" page when an error
     // occurs. By redirecting stdout to stderr, we ensure that all outputs from
     // external processes are visible in case of a failure.

build/rust/build_rust_toolchain_aux.py

@@ -18,6 +18,8 @@ import brave_chromium_utils
 CONFIG_TOML_TEMPLATE = 'config.toml.template'
 TOOLS_RUST = '//tools/rust'
 
+RUST_LLD = 'rust-lld' + ('.exe' if sys.platform == 'win32' else '')
+WASM32_UNKNOWN_UNKNOWN = 'wasm32-unknown-unknown'
 
 def restore_config_toml_template():
     args = [
@@ -100,18 +102,13 @@ def create_archive():
         stage1_output_path = os.path.join(build_rust.RUST_BUILD_DIR,
                                           target_triple, 'stage1', 'lib',
                                           'rustlib')
-        rust_toolchain = os.path.relpath(build_rust.RUST_TOOLCHAIN_OUT_DIR,
-                                         brave_chromium_utils.get_src_dir())
 
-        exe_postfix = '.exe' if sys.platform == 'win32' else ''
         with tarfile.open(package_name(), 'w:xz') as tar:
             tar.add(os.path.join(stage1_output_path, target_triple, 'bin',
-                                 f'rust-lld{exe_postfix}'),
-                    arcname=os.path.join(rust_toolchain, 'bin',
-                                         f'rust-lld{exe_postfix}'))
-            tar.add(os.path.join(stage1_output_path, 'wasm32-unknown-unknown'),
-                    arcname=os.path.join(rust_toolchain, 'lib', 'rustlib',
-                                         'wasm32-unknown-unknown'))
+                                 RUST_LLD),
+                    arcname=RUST_LLD)
+            tar.add(os.path.join(stage1_output_path, WASM32_UNKNOWN_UNKNOWN),
+                    arcname=WASM32_UNKNOWN_UNKNOWN)
 
 
 def main():

build/rust/download_rust_toolchain_aux.py

@@ -0,0 +1,86 @@
+#!/usr/bin/env python3
+# Copyright (c) 2025 The Brave Authors. All rights reserved.
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from urllib.error import HTTPError
+import os
+from pathlib import Path
+import shutil
+import tempfile
+
+import brave_chromium_utils
+import build_rust_toolchain_aux
+import deps
+import deps_config
+
+with brave_chromium_utils.sys_path(build_rust_toolchain_aux.TOOLS_RUST):
+    import build_rust
+    RUST_TOOLCHAIN = build_rust.RUST_TOOLCHAIN_OUT_DIR
+
+BRAVE_RUST_TOOLCHAIN_AUX = os.path.join(RUST_TOOLCHAIN,
+                                        '.brave_rust_toolchain_aux')
+
+
+def is_download_needed():
+    if os.getenv('SKIP_DOWNLOAD_RUST_TOOLCHAIN_AUX', '0') == '1':
+        return False
+
+    package_name = ''
+    try:
+        with open(BRAVE_RUST_TOOLCHAIN_AUX) as file:
+            package_name = file.readline().rstrip()
+    except Exception:
+        pass
+    return package_name != build_rust_toolchain_aux.package_name()
+
+
+def install_package(src_dir):
+    rust_lld_path = os.path.join(RUST_TOOLCHAIN, 'bin',
+                                 build_rust_toolchain_aux.RUST_LLD)
+    wasm32_unknown_unknown_path = os.path.join(
+        RUST_TOOLCHAIN, 'lib', 'rustlib',
+        build_rust_toolchain_aux.WASM32_UNKNOWN_UNKNOWN)
+
+    # delete existing artifacts
+    Path(rust_lld_path).unlink(missing_ok=True)
+    shutil.rmtree(wasm32_unknown_unknown_path, ignore_errors=True)
+
+    # move new artifacts into their final places
+    shutil.move(os.path.join(src_dir, build_rust_toolchain_aux.RUST_LLD),
+                rust_lld_path)
+    shutil.move(
+        os.path.join(src_dir, build_rust_toolchain_aux.WASM32_UNKNOWN_UNKNOWN),
+        wasm32_unknown_unknown_path)
+
+
+def save_package_name():
+    with open(BRAVE_RUST_TOOLCHAIN_AUX, 'w+') as file:
+        file.write(f'{build_rust_toolchain_aux.package_name()}\n')
+
+
+def main():
+    if not is_download_needed():
+        print(f'Skipping {Path(__file__).stem}')
+        return
+
+    with tempfile.TemporaryDirectory(dir=RUST_TOOLCHAIN) as temp_dir:
+        try:
+            deps.DownloadAndUnpack(
+                f'{deps_config.DEPS_PACKAGES_URL}/rust-toolchain-aux/{build_rust_toolchain_aux.package_name()}',
+                temp_dir)
+            install_package(temp_dir)
+            save_package_name()
+        except HTTPError as error:
+            if error.code == 403:
+                print("If you see this error message, "
+                      "it means you're likely on the rebase team "
+                      "and doing a Chromium bump - please visit "
+                      "https://ci.brave.com/view/rust and use your branch "
+                      "to build the required Rust auxiliary package.")
+            raise
+
+
+if __name__ == '__main__':
+    main()

script/deps.py

@@ -1,7 +1,8 @@
 #!/usr/bin/env python
-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
+# Copyright (c) 2025 The Brave Authors. All rights reserved.
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at https://mozilla.org/MPL/2.0/.
 
 """This script is used to download deps."""
 
@@ -87,13 +88,13 @@ def DownloadAndUnpack(url, output_dir, path_prefix=None):
                 assert path_prefix is None
                 extract_zip(tmp_file.name, output_dir)
             else:
-                t = tarfile.open(tmp_file.name, mode='r:gz')
-                members = None
-                if path_prefix is not None:
-                    members = [
-                        m for m in t.getmembers()
-                        if m.name.startswith(path_prefix)
-                    ]
-                t.extractall(path=output_dir, members=members)
+                with tarfile.open(tmp_file.name, mode='r:*') as t:
+                    members = None
+                    if path_prefix is not None:
+                        members = [
+                            m for m in t.getmembers()
+                            if m.name.startswith(path_prefix)
+                        ]
+                    t.extractall(path=output_dir, members=members)
         finally:
             os.unlink(tmp_file.name)