Simplifying adding runenvs in virtual environment

[xq114]

Is your feature request related to a problem? Please describe.

目前在虚拟环境中加环境变量是比较麻烦的：必须先定义一个package，再在on_load里加环境变量，还要加上on_fetch让xmake不报错：

package("__phony")
on_load(function (package)
    package:addenv("PYTHONPATH", path.join(os.scriptdir(), "bin"))
end)
on_fetch(function (package, opt) return {} end)
package_end()
add_requires("__phony")

这种写法繁琐、非常容易出错。然而加环境变量的需求在多语言项目中普遍存在，例如C++/Python混合项目里，编译出的.pyd要在python里测试，就要把python module加入环境变量PYTHONPATH才行

Describe the solution you'd like

目前定义一个add_runenvs()函数就行：

function add_runenvs(envs)
package("__phony")
on_load(function (package)
    package:addenv("TESTFILE", io.readfile("testfile"))
    for name, value in pairs(envs) do
        package:addenv(name, value)
    end
end)
on_fetch(function (package, opt) return {} end)
package_end()
add_requires("__phony")
end

测试：

add_runenvs({TESTENV = path.join(os.scriptdir(), "bin"), TESTENV2 = "", TESTENV3 = winos.version()})

可以正确生成结果。要加入xmake内置函数的话，加一些处理应该就行：

function add_runenvs(envs)
envs = envs or {}
local envnames = table.orderkeys(envs)
if #envnames == 0 then return end -- check input
package("__" .. envnames[1] .. #envnames) -- deduplicate name
on_load(function (package)
    for name, value in pairs(envs) do
        package:addenv(name, value)
    end
end)
on_fetch(function (package, opt) return {} end)
package_end()
add_requires("__" .. envnames[1] .. #envnames)
end

这样多次调用add_runenvs也没有问题了。剩下两个问题：

1. 这种方式的add_runenvs只能定义description scope可用的值。例如需要读取文件，定义 TESTFILE = io.readfile("testfile") ，就只能手写繁琐的package定义了。
2. 这种方式定义的package尽管是fetchonly的空package，仍然会在.xmake/packages产生多余的空文件夹。有没有可能对fetchonly的package不要生成package hash文件夹？

Describe alternatives you've considered

function add_metapackage(load)
package("__phony")
on_load(load)
on_fetch(function (package, opt) return {} end)
package_end()
add_requires("__phony")
end

仍保留package定义的部分给用户，但传入一个on_load函数：

add_metapackage(function (package)
    package:addenv("TESTENV", io.readfile("testfile"))
end)

这样可以解决上面的问题1，只是需要多写一点代码。并且这种形式不仅限于加环境变量，也可以用来做别的事情。（这里去重的话只能用load函数的地址了；我不太清楚怎么做）

Additional context

No response

[waruqi]

试下这个 patch, #5582

脚本，table 描述域设置都可以

includes("@builtin/xrepo")

xrepo_addenvs(function (package)
    package:addenv("FOO", "FOO")
end)

xrepo_addenvs({BAR = "BAR"})

[waruqi]

另外加了一个可以快速设置单个 envs 的

xrepo_addenv("ZOO", "ZOO")

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---

In addition, one can quickly set up a single envs

xrepo_addenv("ZOO", "ZOO")

[xq114]

这种方式定义的package尽管是fetchonly的空package，仍然会在.xmake/packages产生多余的空文件夹。有没有可能对fetchonly的package不要生成package hash文件夹？

这块好像还没解决

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Even though the package defined in this way is a fetchonly empty package, it will still generate extra empty folders in .xmake/packages. Is it possible not to generate a package hash folder for fetchonly packages?

This seems to have not been resolved yet

[waruqi]

这种方式定义的package尽管是fetchonly的空package，仍然会在.xmake/packages产生多余的空文件夹。有没有可能对fetchonly的package不要生成package hash文件夹？

这块好像还没解决

再试试

[Issues-translate-bot]

Bot detected the issue body's language is not English, translate it automatically.

---

Even though the package defined in this way is a fetchonly empty package, it will still generate extra empty folders in .xmake/packages. Is it possible not to generate a package hash folder for fetchonly packages?

This seems to have not been resolved yet

try again

[xq114]

这里实现还是有问题，当加的变量比较复杂（比如路径）

xrepo_addenv("CMAKE_PREFIX_PATH", "C:\\Users\\xq114\\Downloads\\libtorch")

会报错

error: @programdir\core\main.lua:329: @programdir\modules\async\runjobs.lua:325: @programdir\core\package\package.lua:718: cannot create filelock for package(__xrepo_addenv_CMAKE_PREFIX_PATHC:\Users\xq114\Downloads\libtorch)!

去重的时候简单拼接还是不行，会有非法字符，包括xrepo_addenvs使用的table也不行，含有":"字符。理想方式是使用hash，但description scope用不了hash.md5

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---

There are still problems with the implementation here, when the variables added are more complex (such as paths)

xrepo_addenv("CMAKE_PREFIX_PATH", "C:\\Users\\xq114\\Downloads\\libtorch")

Will report an error

error: @programdir\core\main.lua:329: @programdir\modules\async\runjobs.lua:325: @programdir\core\package\package.lua:718: cannot create filelock for package(__xrepo_addenv_CMAKE_PREFIX_PATHC:\Users\ xq114\Downloads\libtorch)!

When removing duplicates, simple splicing still doesn't work. There will be illegal characters, including the table used by xrepo_addenvs, which contains the ":" character. The ideal way is to use hash, but description scope cannot use hash.md5