在Haskell中开发时查看未公开的库函数 [英] View non-exposed library functions while developing in Haskell

问题描述

我在另一个问题中犯了一个错误这可以通过查看

 ：t myfunctionofinterest 
   
 
 
为我在库中使用的函数。
 
 
 
然而，当我在我的项目根目录下，并运行
  $ stack ghci 
  
我的Main.hs包含： 
 
 
  import MyLib 
  
 
 
 
和我的模块一样：
  module MyLib { 
 bunchOfFunctions  - 但不是myfunctionofinterest 
}其中
 
 import SomeDB.ModuleThatExposes  -  myfunctionofinterest 
 
 myfunc :: IO（）
 myfunc = do 
 myfunctionofinterest abc  - 我错误地使用myfunctionofinterest并且可能使用过的地方：t看它有3个参数
  
我不能：t  myfunctionofi因为它没有公开，所以显式导入MyLib.myfunctionofinterest 帮助
，因为它是在导入中定义的。虽然我知道我可以公开它，然后检查它，：a 来编译，然后编辑lib以再次隐藏它，有没有什么可以更快更直接地实现？ 
 
 
 
这似乎是一种常见的模式。当你在开发时需要检查库中使用的类型时，你会做什么？    解决方案

引用 GHCi文档：

：module 命令提供了一种做两件不能完成的事情的方法与普通的进口申报：

• ：模块支持






* 模块上的修饰符可打开模块的完整顶级范围，而不仅仅是导出。

额外的 * 使GHCi加载模块的字节码版本。这不会像性能一样，但是您可以访问未导出的绑定。

示例：

 λ> ：m * MyLib 
λ> ：t myfunctionofinterest 
  

如果您得到

 模块'MyLib'不被解释;尝试'：添加* MyLib的第一个
  

您可能必须执行：load 首先（关于：add 的建议并不总是有效）：

 λ> ：l * MyLib 
λ> ：m * MyLib 
λ> ：t myfunctionofinterest 
  




I made a mistake in another question that could have been solved by viewing

:t myfunctionofinterest

for a function I was using in a library.

However, when I am in my project root, and run

$ stack ghci

And my Main.hs has:

import MyLib

And my module does:

module MyLib {
  bunchOfFunctions -- but not myfunctionofinterest
} where

import SomeDB.ModuleThatExposes -- myfunctionofinterest

myfunc :: IO ()
myfunc = do
  myfunctionofinterest a b c -- place where I misuse myfunctionofinterest and could have used :t on it to see it had 3 args

I can't :t myfunctionofinterest in the main since it's not exposed, nor does Import MyLib.myfunctionofinterest explicitly help, since it was something defined in an import. While I know I could expose it then check it, :a to compile, and then edit the lib to hide it again, is there anything that allows that more quickly and directly?

This seems like it must be a common pattern. What do you do when you need to check the type of something used in a library as you develop?

解决方案

Quoting the GHCi docs:

The :module command provides a way to do two things that cannot be done with ordinary import declarations:

• :module supports the * modifier on modules, which opens the full top-level scope of a module, rather than just its exports.

The additional * makes GHCi load the bytecode version of the module. This will not be as performant, but you'll get access to unexported bindings.

Example:

λ> :m *MyLib
λ> :t myfunctionofinterest

If you get

module 'MyLib' is not interpreted; try ':add *MyLib' first

you may have to do :load first (the advice about :add doesn't always do the trick):

λ> :l *MyLib
λ> :m *MyLib
λ> :t myfunctionofinterest

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