如何获取处于可编辑模式的Conan包的CMake构建目录？

我正尝试推导本地使用CMake构建的Conan包的构建目录，以便在该包处于可编辑模式时设置库目录（libdirs）和二进制目录（bindirs）等路径。理想逻辑如下：

def package_info(self):
    self.cpp_info.libs = [f"{self.name}"]

    # for Conan editable mode
    if not self.in_local_cache:
        self.cpp_info.includedirs = glob.glob("sources/*/include")
        self.cpp_info.libdirs = [f"{cmake_build_dir}/{self.settings.build_type}"]
        self.cpp_info.bindirs = [f"{cmake_build_dir}/{self.settings.build_type}"]

核心问题是找不到可靠的方式获取cmake_build_dir：

• 内部约定是把代码放在sources目录（CMakeLists.txt所在处），在build/win执行CMake，但这只是约定，跨平台构建时需要适配实际结构
• self.build_folder在package_info方法中为空
• 尝试在package_info里创建CMake对象（cmake = CMake(self)）时报错，提示self没有replace属性
• 仅能通过self.recipe_folder获取conanfile.py所在目录

请问有没有简便方法从Conan/CMake获取构建目录，还是只能强制开发者遵循目录约定？

1. 利用Conan的cmake.build_directory配置（推荐） #

Conan本身支持通过配置指定CMake构建目录，你可以在conanfile.py里读取这个配置值，同时允许用户自定义：

import os
from conans import ConanFile, tools

class YourPackage(ConanFile):
    settings = "os", "compiler", "build_type", "arch"

    def package_info(self):
        self.cpp_info.libs = [self.name]
        if not self.in_local_cache:
            # 读取CMake构建目录配置，默认用约定的build/{os}路径
            cmake_build_dir = self.conf.get("tools.cmake.build:directory", 
                                           default=f"build/{self.settings.os.lower()}")
            # 拼接build_type子目录
            build_type_dir = os.path.join(cmake_build_dir, str(self.settings.build_type))
            self.cpp_info.libdirs = [build_type_dir]
            self.cpp_info.bindirs = [build_type_dir]
            self.cpp_info.includedirs = tools.glob("sources/*/include")

用户如果有自定义构建目录，只需要在conan.conf或者命令行里设置：

conan config set tools.cmake.build:directory=my_custom_build_dir

或者在conan editable add时通过--conf传递：

conan editable add . my_package/1.0@user/channel --conf tools.cmake.build:directory=my_build

2. 从CMakeCache.txt反向推导 #

如果用户已经运行过CMake，构建目录里会有CMakeCache.txt，可以通过搜索这个文件来定位构建目录：

import os
from conans import ConanFile, tools

class YourPackage(ConanFile):
    settings = "os", "compiler", "build_type", "arch"

    def package_info(self):
        self.cpp_info.libs = [self.name]
        if not self.in_local_cache:
            # 从recipe_folder开始递归查找CMakeCache.txt
            cmake_cache = tools.find_recursive(self.recipe_folder, "CMakeCache.txt")
            if cmake_cache:
                cmake_build_dir = os.path.dirname(cmake_cache[0])
                build_type_dir = os.path.join(cmake_build_dir, str(self.settings.build_type))
                self.cpp_info.libdirs = [build_type_dir]
                self.cpp_info.bindirs = [build_type_dir]
            else:
                # 找不到时 fallback 到约定目录
                default_build_dir = f"build/{self.settings.os.lower()}"
                build_type_dir = os.path.join(default_build_dir, str(self.settings.build_type))
                self.cpp_info.libdirs = [build_type_dir]
                self.cpp_info.bindirs = [build_type_dir]
            self.cpp_info.includedirs = tools.glob("sources/*/include")

这种方式不需要用户额外配置，但前提是用户已经执行过CMake生成构建目录，第一次运行时可能还是需要依赖约定。

3. 在build方法中保存构建目录到文件 #

在build方法里把CMake的构建路径写入一个临时文件，然后在package_info里读取这个文件：

import os
from conans import ConanFile, CMake, tools

class YourPackage(ConanFile):
    settings = "os", "compiler", "build_type", "arch"
    generators = "cmake"

    def build(self):
        cmake = CMake(self)
        cmake.configure(source_folder="sources")
        cmake.build()
        # 把构建目录写入文件
        build_dir_file = os.path.join(self.recipe_folder, ".conan_build_dir")
        with open(build_dir_file, "w") as f:
            f.write(cmake.build_directory)

    def package_info(self):
        self.cpp_info.libs = [self.name]
        if not self.in_local_cache:
            # 读取保存的构建目录
            build_dir_file = os.path.join(self.recipe_folder, ".conan_build_dir")
            if os.path.exists(build_dir_file):
                with open(build_dir_file, "r") as f:
                    cmake_build_dir = f.read().strip()
            else:
                # fallback 到约定目录
                cmake_build_dir = f"build/{self.settings.os.lower()}"
            build_type_dir = os.path.join(cmake_build_dir, str(self.settings.build_type))
            self.cpp_info.libdirs = [build_type_dir]
            self.cpp_info.bindirs = [build_type_dir]
            self.cpp_info.includedirs = tools.glob("sources/*/include")

这种方式能准确获取CMake实际使用的构建目录，但需要用户先执行过conan build或者在可编辑模式下先构建过包。

不推荐强制目录约定 #

强制约定虽然简单，但会限制用户的自定义构建流程，跨平台时也容易出问题，上面的方法都能在保留灵活性的同时解决问题。

内容的提问来源于stack exchange，提问作者MBraedley