Introduce hermetic MSVC+msbuild toolchain

Author: JSGette

.adms/bazel/adms.mirror.cfg

@@ -113,6 +113,7 @@ rewrite (ftp.osuosl.org)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
 rewrite (gnupg.org)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
 rewrite (kerberos.org)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
 rewrite (packages.microsoft.com)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
+rewrite (download.visualstudio.microsoft.com)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
 rewrite (www.freetds.org)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
 rewrite (www.lua.org)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2
 rewrite (www.sqlite.org)/(.*) depot-read-api-bzl.us1.ddbuild.io/$1/$2

.bazelrc

@@ -80,7 +80,8 @@ common:windows --repo_env=PIP_CACHE_DIR # https://pip.pypa.io/en/stable/topics/c
 common:windows --repo_env=SYSTEMDRIVE # needed by vswhere to locate the VS installer instance database
 common:windows --repo_env=SYSTEMROOT # used by COM to load system DLLs, needed by vswhere
 common:windows --repo_env=USERPROFILE # used by MSYS2 bash to emulate HOME, needed by git to fetch repositories
-common:windows --repo_env=VSTUDIO_ROOT # visual_studio(path_variable) in MODULE.bazel
+common:windows --repo_env=VSTUDIO_ROOT # visual_studio(path_variable) in MODULE.bazel; MSBuild-only
+common:windows --repo_env=BAZEL_TOOLCHAINS_MSVC_ACCEPT_MICROSOFT_VISUAL_STUDIO_BUILDTOOLS_EULA=1 # @toolchains_msvc
 common:windows --run_env=__COMPAT_LAYER=RunAsInvoker # install*.exe may otherwise fail claiming unneeded admin elevation
 common:windows --test_env=__COMPAT_LAYER=RunAsInvoker # same, for bazel test
 common:windows --shell_executable=C:/tools/msys64/usr/bin/bash.exe

MODULE.bazel

@@ -81,6 +81,7 @@ bazel_dep(name = "rules_rust_prost", version = "0.73.0")
 bazel_dep(name = "rules_shell", version = "0.8.0")
 bazel_dep(name = "toml.bzl", version = "0.4.1")
 bazel_dep(name = "toolchains_llvm", version = "1.8.0")
+bazel_dep(name = "toolchains_msvc", version = "0.1.0")
 
 bazel_dep(name = "rules_testing", version = "0.9.0", dev_dependency = True)
 
@@ -261,6 +262,16 @@ use_repo(linux_headers_ext, "linux_headers", "linux_headers_aarch64", "linux_hea
 ## Compilers and toolchains        ##
 ####################################
 
+git_override(
+    module_name = "toolchains_msvc",
+    commit = "8e2aa4624bbb5a53a94f135e90995f307875d1ad",
+    patch_strip = 1,
+    # Adds MSBuild + the VC project system, and whole-tree filegroups, so MSBuild-driven
+    # builds (CPython) can run against the same hermetic toolchain as rules_cc.
+    patches = ["//bazel/patches:toolchains_msvc/0001-hermetic-msbuild-and-toolchain-trees.patch"],
+    remote = "https://github.com/Dragnalith/toolchains_msvc",
+)
+
 archive_override(
     module_name = "gcc_toolchain",
     patch_args = ["-p1"],
@@ -361,20 +372,35 @@ winlibs_mingw_repository(
     url = "https://github.com/brechtsanders/winlibs_mingw/releases/download/14.2.0posix-19.1.7-12.0.0-msvcrt-r3/winlibs-x86_64-posix-seh-gcc-14.2.0-mingw-w64msvcrt-12.0.0-r3.zip",
 )
 
+# Hermetic MSVC + Windows SDK for rules_cc (cl/link), and MSBuild for CPython
+# (see deps/cpython/build_python.bat). MinGW stays the default Windows cc_toolchain.
+msvc_toolchain = use_extension("@toolchains_msvc//:extensions.bzl", "toolchain")
+msvc_toolchain.toolchain_set(
+    name = "default",
+    # MSVC toolset version, not VS product version: VS 2022 17.14.x → 14.44
+    # (see https://learn.microsoft.com/en-us/cpp/overview/compiler-versions).
+    # toolchains_msvc only accepts 14.xx here, not 17.14.
+    msvc_versions = ["14.44"],
+    # Win11 SDK 10.0.26100; toolchains_msvc uses the trailing build number only.
+    winsdk_versions = ["26100"],
+)
+use_repo(msvc_toolchain, "msvc_toolchains")
+
 # TODO{agent-build}: Find a way to register platform-specific toolchains dynamically
 register_toolchains(
     "@gcc_toolchain_x86_64//:cc_toolchain",
     "@gcc_toolchain_aarch64//:cc_toolchain",
     "@gcc_toolchain_armv7//:cc_toolchain",
     "@winlibs_mingw64//:mingw_cc_toolchain",
+    "@msvc_toolchains//:all",
     "@llvm_toolchain//:all",  # last to avoid taking precedence over GCC toolchains
 )
 
-# Visual Studio / MSBuild tooling, taken from the local installation
+# Host MSBuild for the DatadogInterop vcxproj only; CPython uses the hermetic
+# @msvc_toolchains//msbuild instead.
 visual_studio(
     name = "visual_studio",
     path_variable = "VSTUDIO_ROOT",
-    version = "17.14.36717.8",  # 18.4.11612.150
 )
 
 # =========================================