包括Bazel http_file下载的文件

Question

我正在使用Bazel来构建我的项目。我想使用单头测试框架Catchv2。我决定使用http_file规则让Bazel下载catch头。我的WORKSPACE文件如下所示：

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_file")
http_file(
  name = "catch",
  downloaded_file_path = "catch.hpp",
  sha256 = "cc6cc272cf84d8e10fb28f66f52584dedbb80d1234aae69e6a1027af4f31ae6f",
  urls = ["https://github.com/catchorg/Catch2/releases/download/v2.4.2/catch.hpp"],
)

根据文档，测试取决于生成的包，如下所示：

cc_test(
  name = "my_test",
  srcs = ["@catch//file", "my_test.cc"]
)

测试文件my_test.cc再简单不过了：

#include "catch.hpp"

然而，我得到以下错误：

$ bazel test --config=opt -s //...
WARNING: [...]/BUILD:25:10: in srcs attribute of cc_test rule //test:my_test: please do not import '@catch//file:catch.hpp' directly. You should either move the file to this package or depend on an appropriate rule there
SUBCOMMAND: # //test:my_test [action 'Compiling test/my_test.cc']
(cd [...] && 
  exec env - [...] 
  /usr/bin/gcc
 -U_FORTIFY_SOURCE -fstack-protector -Wall -B/usr/bin -B/usr/bin -Wunused-but-set-parameter -Wno-free-nonheap-object -fno-omit-frame-pointer '-std=c++0x' -MD -MF [...].d '-frandom-seed=[...].o' -fPIC
 -iquote .
 -iquote bazel-out/k8-fastbuild/genfiles
 -iquote bazel-out/k8-fastbuild/bin
 -iquote external/bazel_tools
 -iquote bazel-out/k8-fastbuild/genfiles/external/bazel_tools
 -iquote bazel-out/k8-fastbuild/bin/external/bazel_tools
 -fno-canonical-system-headers -Wno-builtin-macro-redefined '-D__DATE__="redacted"' '-D__TIMESTAMP__="redacted"' '-D__TIME__="redacted"' -c test/my_test.cc
 -o [...].o)
ERROR: [...]/BUILD:23:1: C++ compilation of rule '//test:my_test' failed (Exit 1)
test/my_test.cc:1:28: fatal error: catch.hpp: No such file or directory
compilation terminated.
[...]
FAILED: Build did NOT complete successfully

创建cc_library包装或包含catch/catch.hpp、catch/file/catch.hpp也会产生同样的错误。

Answer 1

默认情况下，http_file下载的文件可以包含为：

#include "external/<name>/file/<file_name>"

在这种特定情况下：

#include "external/catch/file/catch.hpp"

但是，这个include路径很难看，它应该用cc_library来包装。此外，为每个测试编译完整的catch头文件会使构建速度变慢。根据catch文档，catch头的实现部分应该单独编译。像这样：

测试/构建：

cc_library(
  name = "catch",
  hdrs = ["@catch//file"],
  srcs = ["catch.cpp"],
  visibility = ["//visibility:public"],
  strip_include_prefix = "/external/catch/file",
  include_prefix = "catch",
  linkstatic = True,   # otherwise main() will could end up in a .so
)
cc_test(
  name = "my_test",
  deps = ["//test:catch"],
  srcs = ["my_test.cc"],
)

test/catch.cpp:

#define CATCH_CONFIG_MAIN
#include "catch/catch.hpp"

测试/my_test.cc:

#include "catch/catch.hpp"
TEST_CASE("my_test", "[main]") { /* ... */ }

这样，如果只有my_test.cc发生更改，则不会重新编译catch.cpp，从而节省宝贵的秒数。