如何使用仍然使用 runhaskell/ghci 运行的库+可执行文件制作 Haskell Cabal 项目?

问题描述

如果您在阴谋集团中声明一个库 + 可执行部分文件同时通过将库放入hs-source-dirs 目录来避免库的双重编译，您通常无法使用ghci 和 运行您的项目>runhaskell，尤其是当可执行文件本身有帮助模块时.

If you declare a library + executable sections in a cabal file while avoiding double compilation of the library by putting the library into a hs-source-dirs directory, you cannot usually run your project with ghci and runhaskell anymore, especially if the executables have helper modules themselves.

推荐的项目布局是什么

• 只构建一次需要的东西
• 允许使用 runhaskell
• 结构简洁，没有黑客攻击?

推荐答案

假设你有一个 mylib 库，以及 mylib-commandline 和 mylib-server 可执行文件.

Let's assume you have a mylib library, and mylib-commandline and mylib-server executables.

您对库和每个可执行文件使用 hs-source-dirs，这样每个可执行文件都有自己的项目根目录，避免双重编译:

You use hs-source-dirs for the library and each executable so that each has their own project root, avoiding double compilation:

mylib/                      # Project root
  mylib.cabal
  src/                      # Root for the library
  tests/
  mylib-commandline/        # Root for the command line utility + helper modules
  mylib-server/             # Root for the web service + helper modules

完整目录布局:

mylib/                      # Project root
  mylib.cabal
  src/                      # Root for the library
    Web/
      Mylib.hs              # Main library module
      Mylib/
        ModuleA             # Mylib.ModuleA
        ModuleB             # Mylib.ModuleB
  tests/
    ...
  mylib-commandline/        # Root for the command line utility
    Main.hs                 # "module Main where" stub with "main = Web.Mylib.Commandline.Main.main"
    Web/
      Mylib/
        Commandline/
          Main.hs           # CLI entry point
          Arguments.hs      # Programm command line arguments parser
  mylib-server/             # Root for the web service
    Server.hs               # "module Main where" stub with "main = Web.Mylib.Server.Main.main"
    Web/
      Mylib/
        Server/
          Main.hs           # Server entry point
          Arguments.hs      # Server command line arguments parser

stub-like 入口点文件 mylib-commandline/Main.hs 看起来像这样:

The stub-like entry point file mylib-commandline/Main.hs looks like this:

module Main where

import qualified Web.Mylib.Server.Main as MylibServer

main :: IO ()
main = MylibServer.main

您需要它们，因为 executable 必须从一个简单的名为 Main 的模块开始.

You need them because an executable must start on a module simply called Main.

你的 mylib.cabal 看起来像这样:

Your mylib.cabal looks like this:

library
  hs-source-dirs:   src
  exposed-modules:
    Web.Mylib
    Web.Mylib.ModuleA
    Web.Mylib.ModuleB
  build-depends:
      base >= 4 && <= 5
    , [other dependencies of the library]

executable mylib-commandline
  hs-source-dirs:   mylib-commandline
  main-is:          Main.hs
  other-modules:
    Web.Mylib.Commandline.Main
    Web.Mylib.Commandline.Arguments
  build-depends:
      base >= 4 && <= 5
    , mylib
    , [other depencencies for the CLI]

executable mylib-server
  hs-source-dirs:   mylib-server
  main-is:          Server.hs
  other-modules:
    Web.Mylib.Server.Main
  build-depends:
      base >= 4 && <= 5
    , mylib
    , warp >= X.X
    , [other dependencies for the server]

cabal build 将构建库和两个可执行文件，无需对库进行双重编译，因为每个文件都在自己的 hs-source-dirs 中，并且可执行文件依赖于图书馆.

cabal build will build the library and the two executables without double compilation of the library, because each is in their own hs-source-dirs and the executables depend on the library.

你仍然可以从你的项目根目录运行带有 runghc 的可执行文件，使用 -i 开关来告诉它应该在哪里寻找模块(使用 : 作为分隔符):

You can still run the executables with runghc from your project root, using the -i switch to tell where it shall look for modules (using : as separator):

runhaskell -isrc:mylib-commandline mylib-commandline/Main.hs

runhaskell -isrc:mylib-server mylib-server/Server.hs

通过这种方式，您可以拥有干净的布局、带有辅助模块的可执行文件，并且所有内容仍然可以使用 runhaskell/runghc 和 ghci.为了避免重复输入这个标志，你可以添加类似

This way, you can have a clean layout, executables with helper modules, and everything still works with runhaskell/runghc and ghci. To avoid typing this flag repeatedly, you can add something similar to

:set -isrc:mylib-commandline:mylib-server

到您的 .ghci 文件.

请注意，有时应该将您的代码拆分为单独的包，例如mylib、mylib-commandline 和 mylib-server.

Note that sometimes should split your code into separate packages, e.g. mylib, mylib-commandline and mylib-server.

这篇关于如何使用仍然使用 runhaskell/ghci 运行的库+可执行文件制作 Haskell Cabal 项目?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！