如何在Bazel中实现非原生自定义构建配置与变体管理

步骤1：定义变体维度约束 #

首先在工作区根目录的BUILD文件中定义你需要的三个变体维度对应的约束：

# 定义约束维度
constraint_setting(name = "has_hw_x")
constraint_value(
    name = "hw_x_enabled",
    constraint_setting = ":has_hw_x",
)
constraint_value(
    name = "hw_x_disabled",
    constraint_setting = ":has_hw_x",
)

constraint_setting(name = "connect_interface")
constraint_value(
    name = "interface_eth",
    constraint_setting = ":connect_interface",
)
constraint_value(
    name = "interface_usb",
    constraint_setting = ":connect_interface",
)
constraint_value(
    name = "interface_uart",
    constraint_setting = ":connect_interface",
)

constraint_setting(name = "fail_fast")
constraint_value(
    name = "fail_fast_enabled",
    constraint_setting = ":fail_fast",
)
constraint_value(
    name = "fail_fast_disabled",
    constraint_setting = ":fail_fast",
)

步骤2：定义预设配置 #

还是在根目录BUILD文件中，把你需要的4种预设配置对应到上面的约束组合：

# 客户配置1
config_setting(
    name = "customer1",
    constraint_values = [
        ":hw_x_enabled",
        ":interface_eth",
        ":fail_fast_enabled",
    ],
)

# 客户配置2
config_setting(
    name = "customer2",
    constraint_values = [
        ":hw_x_enabled",
        ":interface_usb",
        ":fail_fast_enabled",
    ],
)

# 客户配置3
config_setting(
    name = "customer3",
    constraint_values = [
        ":hw_x_disabled",
        ":interface_usb",
        ":fail_fast_disabled",
    ],
)

# 硬件调试配置
config_setting(
    name = "debughw",
    constraint_values = [
        ":hw_x_disabled",
        ":interface_uart",
        ":fail_fast_enabled",
    ],
)

步骤3：满足各项需求的实现 #

1. 通用目标默认兼容所有配置，专属组件指定适配 #

• 普通目标不需要做任何修改，天然支持所有配置构建，新增配置时只需要新增上面的config_setting定义，不需要修改原有目标。
• 仅适配特定配置的组件，直接在属性中声明即可，比如仅硬件调试配置可用的组件：

cc_library(
    name = "hw_debug_only_component",
    srcs = ["debug.c"],
    target_compatible_with = [":hw_x_disabled", ":interface_uart"],
)

2. 按配置自动添加编译标记 #

在编译属性中通过select()匹配约束值即可，示例：

cc_library(
    name = "common_lib",
    srcs = ["common.c"],
    copts = select({
        ":interface_eth": ["-DVARIANT_POINT_CONNECTED_ETH"],
        ":interface_usb": ["-DVARIANT_POINT_CONNECTED_USB"],
        ":interface_uart": ["-DVARIANT_POINT_CONNECTED_UART"],
        "//conditions:default": [],
    }) + select({
        ":hw_x_enabled": ["-DHW_X_ENABLED"],
        "//conditions:default": [],
    }),
)

3. 简化构建命令 #

有两种实现方式可选：

方式1：用--config参数（更简单）

在工作区根目录的.bazelrc文件中添加如下配置：

build:customer1 --constraint_value=//:hw_x_enabled --constraint_value=//:interface_eth --constraint_value=//:fail_fast_enabled
build:customer2 --constraint_value=//:hw_x_enabled --constraint_value=//:interface_usb --constraint_value=//:fail_fast_enabled
build:customer3 --constraint_value=//:hw_x_disabled --constraint_value=//:interface_usb --constraint_value=//:fail_fast_disabled
build:debughw --constraint_value=//:hw_x_disabled --constraint_value=//:interface_uart --constraint_value=//:fail_fast_enabled

之后就可以直接用对应命令构建：
bazel build //my/target --config=debughw

方式2：自定义全局flag（符合你期望的命令格式）

在根目录BUILD文件中添加自定义flag和配置转换逻辑：

load("@bazel_skylib//rules:common_settings.bzl", "string_flag")

string_flag(
    name = "configuration",
    build_setting_default = "customer1",
    values = ["customer1", "customer2", "customer3", "debughw"],
)

# 绑定flag值到对应约束
config_setting(
    name = "use_customer1",
    flag_values = {":configuration": "customer1"},
)
config_setting(
    name = "use_customer2",
    flag_values = {":configuration": "customer2"},
)
config_setting(
    name = "use_customer3",
    flag_values = {":configuration": "customer3"},
)
config_setting(
    name = "use_debughw",
    flag_values = {":configuration": "debughw"},
)

之后就可以用你期望的命令格式构建：
bazel build //my/target --//:configuration=debughw

内容的提问来源于stack exchange，提问作者Andreas