fix(uv): select configured native build tools

docs/uv-patching.md

@@ -203,6 +203,13 @@ uv.override_package(
   convey them.
 - Generated pure-Python builds reject `toolchains` and `env`; those attributes
   augment the native build toolchain and environment.
+- Native build `env` values can use `$(EXECROOT)/` to anchor paths supplied by
+  a toolchain, for example `CPPFLAGS = "-I$(EXECROOT)/$(DEP_INC)"` and
+  `LDFLAGS = "$(EXECROOT)/$(DEP_LIB_A)"`. The anchor remains valid after the
+  PEP 517 backend changes into the unpacked source tree.
+- Native builds select the configured C++ compiler, archiver, linker, and strip
+  tools by default. Explicit `CC`, `CXX`, `AR`, `LD`, and `STRIP` values in
+  `env` override those selections.
 - Post-install patches to prebuilt wheels must preserve every original path
   used for collision and regular-package merge planning, including its
   file-or-directory kind and package classification. Ordinary added paths are

e2e/cases/pep517-frontend-exec-group/BUILD.bazel

@@ -2,11 +2,19 @@ load("@aspect_rules_py//uv/private/pep517_whl:rule.bzl", "pep517_native_whl")
 load("@bazel_lib//lib:transitions.bzl", "platform_transition_filegroup")
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
+load("@rules_cc//cc/toolchains:cc_toolchain.bzl", legacy_cc_toolchain = "cc_toolchain")
+load("@rules_cc//cc/toolchains:tool.bzl", "cc_tool")
+load("@rules_cc//cc/toolchains:tool_map.bzl", "cc_tool_map")
+load("@rules_cc//cc/toolchains:toolchain.bzl", "cc_toolchain")
 load("@rules_shell//shell:sh_binary.bzl", "sh_binary")
-load(":toolchain.bzl", "fake_cc_toolchain")
+load(":toolchain.bzl", "fake_cc_toolchain", "legacy_cc_toolchain_config")
 
 _CC_TOOLCHAIN = "//pep517-frontend-exec-group:cc_toolchain"
 
+_CONFIGURED_CC_TOOLCHAIN = "//pep517-frontend-exec-group:configured_cc_toolchain"
+
+_LEGACY_CC_TOOLCHAIN = "//pep517-frontend-exec-group:legacy_cc_toolchain"
+
 # Keep the host first so the default exec group selects it. The native wheel's
 # `target` exec group requires the transitioned target constraints and selects
 # the second platform instead. Platform flags are applied in the configuration
@@ -38,6 +46,32 @@ platform(
     ],
 )
 
+platform(
+    name = "linux_configured",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+    flags = [
+        "--@aspect_rules_py//uv/private/constraints/platform:platform_libc=glibc",
+        "--extra_execution_platforms=@platforms//host,//pep517-frontend-exec-group:linux_configured",
+        "--extra_toolchains=" + _CONFIGURED_CC_TOOLCHAIN,
+    ],
+)
+
+platform(
+    name = "linux_legacy",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+    flags = [
+        "--@aspect_rules_py//uv/private/constraints/platform:platform_libc=glibc",
+        "--extra_execution_platforms=@platforms//host,//pep517-frontend-exec-group:linux_legacy",
+        "--extra_toolchains=" + _LEGACY_CC_TOOLCHAIN,
+    ],
+)
+
 config_setting(
     name = "linux_aarch64_config",
     constraint_values = [
@@ -92,6 +126,90 @@ toolchain(
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 )
 
+write_file(
+    name = "unusual_c_driver",
+    out = "unusual_c_driver.sh",
+    content = [
+        "#!/usr/bin/env bash",
+        "printf '%s\\n' c-action",
+    ],
+    is_executable = True,
+)
+
+write_file(
+    name = "unusual_cxx_driver",
+    out = "unusual_cxx_driver.sh",
+    content = [
+        "#!/usr/bin/env bash",
+        "printf '%s\\n' cxx-action",
+    ],
+    is_executable = True,
+)
+
+cc_tool(
+    name = "configured_c_tool",
+    src = ":unusual_c_driver",
+)
+
+cc_tool(
+    name = "configured_cxx_tool",
+    src = ":unusual_cxx_driver",
+)
+
+cc_tool_map(
+    name = "configured_tool_map",
+    tools = {
+        "@rules_cc//cc/toolchains/actions:c_compile": ":configured_c_tool",
+        "@rules_cc//cc/toolchains/actions:cpp_compile_actions": ":configured_cxx_tool",
+        "@rules_cc//cc/toolchains/actions:link_actions": ":configured_c_tool",
+        "@rules_cc//cc/toolchains/actions:strip": ":configured_c_tool",
+        "@rules_cc//cc/toolchains/actions:ar_actions": ":configured_c_tool",
+    },
+)
+
+cc_toolchain(
+    name = "configured_cc",
+    tool_map = ":configured_tool_map",
+)
+
+toolchain(
+    name = "configured_cc_toolchain",
+    toolchain = ":configured_cc",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+)
+
+filegroup(
+    name = "legacy_tools",
+    srcs = [
+        "legacy_archiver.sh",
+        "legacy_compiler.sh",
+    ],
+)
+
+legacy_cc_toolchain_config(
+    name = "legacy_cc_config",
+    archiver = "legacy_archiver.sh",
+    compiler = "legacy_compiler.sh",
+)
+
+legacy_cc_toolchain(
+    name = "legacy_cc",
+    all_files = ":legacy_tools",
+    ar_files = ":legacy_tools",
+    compiler_files = ":legacy_tools",
+    dwp_files = ":legacy_tools",
+    linker_files = ":legacy_tools",
+    objcopy_files = ":legacy_tools",
+    strip_files = ":legacy_tools",
+    toolchain_config = ":legacy_cc_config",
+)
+
+toolchain(
+    name = "legacy_cc_toolchain",
+    toolchain = ":legacy_cc",
+    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
+)
+
 write_file(
     name = "frontend_script",
     out = "frontend.sh",
@@ -124,6 +242,66 @@ sh_binary(
     srcs = [":frontend_script"],
 )
 
+write_file(
+    name = "configured_frontend_script",
+    out = "configured_frontend.sh",
+    content = [
+        "#!/usr/bin/env bash",
+        "set -euo pipefail",
+        "c_actual=\"$(\"${CC}\")\"",
+        "cxx_actual=\"$(\"${CXX}\")\"",
+        "if [[ \"${c_actual}\" != c-action || \"${cxx_actual}\" != cxx-action ]]; then",
+        "  echo \"configured tools reported ${c_actual} and ${cxx_actual}\" >&2",
+        "  exit 1",
+        "fi",
+        "wheel_dir=\"${!#}\"",
+        "mkdir -p \"${wheel_dir}\"",
+    ],
+    is_executable = True,
+)
+
+sh_binary(
+    name = "configured_frontend",
+    srcs = [":configured_frontend_script"],
+)
+
+write_file(
+    name = "legacy_frontend_script",
+    out = "legacy_frontend.sh",
+    content = [
+        "#!/usr/bin/env bash",
+        "set -euo pipefail",
+        "execroot=\"${PWD}\"",
+        "if [[ \"${AR-unset}\" != */legacy_archiver.sh || \"${CC-unset}\" != */legacy_compiler.sh || \"${CXX-unset}\" != */legacy_compiler.sh || \"${LD-unset}\" != */legacy_compiler.sh || \"${STRIP-unset}\" != */legacy_compiler.sh ]]; then",
+        "  echo \"legacy tools were not selected: AR=${AR-unset} CC=${CC-unset} CXX=${CXX-unset} LD=${LD-unset} STRIP=${STRIP-unset}\" >&2",
+        "  exit 1",
+        "fi",
+        "wheel_dir=\"${!#}\"",
+        "wheel_dir=\"${execroot}/${wheel_dir}\"",
+        "work_dir=\"${wheel_dir}.tmp\"",
+        "/bin/mkdir -p \"${wheel_dir}\" \"${work_dir}/poison\"",
+        "for tool in cc c++ ar ld strip; do",
+        "  printf '%s\\n' '#!/bin/sh' 'echo ambient tool selected >&2' 'exit 97' > \"${work_dir}/poison/${tool}\"",
+        "  /bin/chmod +x \"${work_dir}/poison/${tool}\"",
+        "done",
+        "export PATH=\"${work_dir}/poison:/usr/bin:/bin\"",
+        "cd \"${work_dir}\"",
+        "printf '%s\\n' 'int c_value(void) { return 42; }' > dep.c",
+        "printf '%s\\n' 'extern \"C\" int c_value(void);' 'int main() { return c_value() == 42 ? 0 : 1; }' > main.cc",
+        "\"${execroot}/${CC}\" -c dep.c -o dep.o",
+        "\"${execroot}/${AR}\" rcs libdep.a dep.o",
+        "\"${execroot}/${CXX}\" -c main.cc -o main.o",
+        "\"${execroot}/${CXX}\" main.o libdep.a -o native",
+        "./native",
+    ],
+    is_executable = True,
+)
+
+sh_binary(
+    name = "legacy_frontend",
+    srcs = [":legacy_frontend_script"],
+)
+
 write_file(
     name = "stub_sdist",
     out = "stub.tar.gz",
@@ -142,6 +320,22 @@ pep517_native_whl(
     version = "0.0.0",
 )
 
+pep517_native_whl(
+    name = "configured_wheel",
+    src = ":stub_sdist",
+    tags = ["manual"],
+    tool = ":configured_frontend",
+    version = "0.0.0",
+)
+
+pep517_native_whl(
+    name = "legacy_wheel",
+    src = ":stub_sdist",
+    tags = ["manual"],
+    tool = ":legacy_frontend",
+    version = "0.0.0",
+)
+
 platform_transition_filegroup(
     name = "wheel_linux_aarch64",
     srcs = [":wheel"],
@@ -154,10 +348,32 @@ platform_transition_filegroup(
     target_platform = ":linux_x86_64",
 )
 
+platform_transition_filegroup(
+    name = "wheel_linux_configured",
+    srcs = [":configured_wheel"],
+    target_platform = ":linux_configured",
+)
+
+platform_transition_filegroup(
+    name = "wheel_linux_legacy",
+    srcs = [":legacy_wheel"],
+    target_platform = ":linux_legacy",
+)
+
 build_test(
     name = "frontend_exec_platform_test",
     targets = [
         ":wheel_linux_aarch64",
         ":wheel_linux_x86_64",
     ],
 )
+
+build_test(
+    name = "configured_compiler_tools_test",
+    targets = [":wheel_linux_configured"],
+)
+
+build_test(
+    name = "legacy_toolchain_test",
+    targets = [":wheel_linux_legacy"],
+)

e2e/cases/pep517-frontend-exec-group/legacy_archiver.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+export PATH=/usr/bin:/bin
+exec /usr/bin/ar "$@"

e2e/cases/pep517-frontend-exec-group/legacy_compiler.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+export PATH=/usr/bin:/bin
+exec /usr/bin/cc "$@"

e2e/cases/pep517-frontend-exec-group/toolchain.bzl

@@ -1,5 +1,9 @@
 """Synthetic C++ toolchains for the PEP 517 execution-group test."""
 
+load("@rules_cc//cc:cc_toolchain_config_lib.bzl", "feature", "tool_path")  # buildifier: disable=deprecated-function
+load("@rules_cc//cc/common:cc_common.bzl", "cc_common")
+load("@rules_cc//cc/toolchains:cc_toolchain_config_info.bzl", "CcToolchainConfigInfo")
+
 def _fake_cc_toolchain_impl(ctx):
     compiler = ctx.file.compiler
     return [
@@ -18,3 +22,39 @@ fake_cc_toolchain = rule(
         ),
     },
 )
+
+def _legacy_cc_toolchain_config_impl(ctx):
+    compiler = ctx.file.compiler.basename
+    return cc_common.create_cc_toolchain_config_info(
+        ctx = ctx,
+        toolchain_identifier = "legacy-no-action-configs",
+        host_system_name = "local",
+        target_system_name = "local",
+        target_cpu = "x86_64",
+        target_libc = "unknown",
+        compiler = "legacy",
+        abi_version = "unknown",
+        abi_libc_version = "unknown",
+        features = [feature(name = "no_legacy_features", enabled = True)],
+        tool_paths = [
+            tool_path(name = "ar", path = ctx.file.archiver.basename),
+            tool_path(name = "cpp", path = compiler),
+            tool_path(name = "dwp", path = compiler),
+            tool_path(name = "gcc", path = compiler),
+            tool_path(name = "gcov", path = compiler),
+            tool_path(name = "ld", path = compiler),
+            tool_path(name = "nm", path = compiler),
+            tool_path(name = "objcopy", path = compiler),
+            tool_path(name = "objdump", path = compiler),
+            tool_path(name = "strip", path = compiler),
+        ],
+    )
+
+legacy_cc_toolchain_config = rule(
+    implementation = _legacy_cc_toolchain_config_impl,
+    attrs = {
+        "archiver": attr.label(allow_single_file = True, mandatory = True),
+        "compiler": attr.label(allow_single_file = True, mandatory = True),
+    },
+    provides = [CcToolchainConfigInfo],
+)