Bazel 选择在 ctx.file 中失败

Question

我正在尝试根据运行 bazel 的操作系统指定构建条件，因此在我的 .bzl 脚本中我有一个规则，该规则从外部源创建所有模拟链接并编写一个构建文件(使用 ctx.file) ，我在其中声明了所有导入和库，并且在其中我想添加选择功能。但是，当我构建时收到此错误消息:

ERROR: no such package '@maya_repo//': Traceback (most recent call last):
        File "/var/tmp/doNotRemove/mdilena_plugins/MayaMathNodes/src/maya.bzl", line 149
                ctx.file("BUILD", _BUILD_STRUC.format(maya_...))
        File "/var/tmp/doNotRemove/mdilena_plugins/MayaMathNodes/src/maya.bzl", line 149, in ctx.file
                _BUILD_STRUC.format(maya_dir = maya_dir)
Invalid character '[' inside replacement field

下面是我的代码示例以及我要实现的目标:

_BUILD_STRUC = \
"""
# Windows imports
cc_import(
    name = "Foundation-win",
    interface_library = "{maya_dir}/lib/Foundation.lib",
    shared_library = "{maya_dir}/bin/Foundation.dll",
)

cc_import(
    name = "OpenMaya-win",
    interface_library = "{maya_dir}/lib/OpenMaya.lib",
    shared_library = "{maya_dir}/bin/OpenMaya.dll",
)

# Linux imports
cc_import(
    name = "Foundation-lnx",
    shared_library = "{maya_dir}/bin/Foundation.so",
)

cc_import(
    name = "OpenMaya-lnx",
    shared_library = "{maya_dir}/bin/OpenMaya.so",
)

cc_library(
    name = "Foundation",
    deps = select({
        "@bazel_tools//src/conditions:windows": [":Foundation-win"],
        "//conditions:default": [":Foundation-lnx"],
        }),
    includes = ["{maya_dir}/include"],
    visibility = ["//visibility:public"],
)

cc_library(
    name = "OpenMaya",
    deps = select({
        "@bazel_tools//src/conditions:windows": [":OpenMaya-win"],
        "//conditions:default": [":OpenMaya-lnx"],
        }),
    includes = ["{maya_dir}/include"],
    visibility = ["//visibility:public"],
)
"""

def _impl(ctx):
    maya_src = ctx.os.environ["MAYA_LOCATION"]
    maya_ver = ctx.os.environ["MAYA_VERSION"]
    maya_dir = "maya{}".format(maya_ver)
    ctx.symlink(maya_src, maya_dir)
    ctx.file("BUILD", _BUILD_STRUC.format(maya_dir=maya_dir))


link_maya = repository_rule(
    implementation = _impl,
    local = True,
    environ = ["MAYA_LOCATION"],
)

有人知道为什么会这样吗？我看了select和 configurable attributes文档，似乎这就是使用它的方式；我想知道是我做错了什么还是某处有错误。

感谢您的帮助!

EDIT:

looks like Bazel really doesn't like using select inside a ctx.file, I'll leave the question open in case someone will be able to shed some light on it. In the meantime I solved it by making all the cc_imports and includes public from the linked repo, while leaving all the cc_libraries with select to my plugin's BUILD file; from there I'm able to use the condition and everything builds.

Answer 1

看起来错误来自这一行，特别是对 string.format 的调用.

ctx.file("BUILD", _BUILD_STRUC.format(maya_dir=maya_dir))

string.format 在模板字符串中搜索大括号，例如 {} 或 {key}，并用位置参数或关键字参数替换它们。

您看到此错误是因为 string.format 将模板中 select 的 dict 参数误认为是要替换的内容，因为它以花括号开头。通过加倍转义模板字符串中的大括号应该可以解决问题:

_BUILD_STRUC = \
"""
...
cc_library(
    name = "Foundation",
    deps = select({{
        "@bazel_tools//src/conditions:windows": [":Foundation-win"],
        "//conditions:default": [":Foundation-lnx"],
        }}),
    includes = ["{maya_dir}/include"],
    visibility = ["//visibility:public"],
)
...

仅供引用，您可能会找到 repository_ctx.template更容易使用。它的语义略有不同:它按字面替换字符串，而不寻找像 { 这样的特殊字符，因此不需要转义。