强制 R 函数调用自给自足

我正在寻找一种方法来调用不受其他对象影响的函数.GlobalEnv.

看一下下面两个函数：

y = 3
f1 = function(x) x+y

f2 = function(x) {
   library(dplyr)
   x %>%
       mutate(area = Sepal.Length *Sepal.Width) %>%
       head()
}

在这种情况下：

• f1(5)应该失败，因为y未在函数作用域中定义
• f2(iris)应该通过，因为该函数不会引用其范围之外的变量

现在，我可以覆盖环境f1 and f2，要么baseenv() or new.env(parent=environment(2L)):

environment(f1) = baseenv()
environment(f2) = baseenv()
f1(3)    # fails, as it should
f2(iris) # fails, because %>% is not in function env

or:

# detaching here makes `dplyr` inaccessible for `f2`
# not detaching leaves `head` inaccessible for `f2`
detach("package:dplyr", unload=TRUE)
environment(f1) = new.env(parent=as.environment(2L))
environment(f2) = new.env(parent=as.environment(2L))
f1(3)    # fails, as it should
f2(iris) # fails, because %>% is not in function env

有没有办法覆盖函数的环境，使其必须自给自足，但只要加载自己的库，它就始终可以工作？

The problem here is, fundamentally, that library and similar tools don’t provide scoping, and are not designed to be made to work with scopes:¹ Even though library is executed inside the function, its effect is actually global, not local. Ugh.

具体来说，您将函数与全局环境隔离的方法是声音；然而，library操纵search路径（通过attach），并且函数的环境不会被“通知”这一点：它仍然会指向previous第二个搜索路径条目作为其祖父母。

你需要找到一种方法updating函数环境的祖父母环境library/attach/…被调用。您可以通过替换来实现此目的library等等，在函数的父环境中使用您自己的版本调用修改版本attach. This attach2那么不仅会调用原来的attach还要重新链接您的环境的父级。

¹ As an aside, ‘box https://klmr.me/box/’ fixes all of these problems. Replacing library(foo) with box::use(foo[...]) in your code makes it work. This is because modules are strongly scoped and environment-aware.