由cabal在包名下创建的.cabal文件中出现语法错误

Question

我有一个名为day-2的目录(与问题无关，只是通过代码的到来)，在其中运行cabal init。

这个init命令生成一个day-2.cabal文件：

cabal-version:      3.4
-- The cabal-version field refers to the version of the .cabal specification,
-- and can be different from the cabal-install (the tool) version and the
-- Cabal (the library) version you are using. As such, the Cabal (the library)
-- version used must be equal or greater than the version stated in this field.
-- Starting from the specification version 2.2, the cabal-version field must be
-- the first thing in the cabal file.

-- Initial package description 'day-2' generated by
-- 'cabal init'. For further documentation, see:
--   http://haskell.org/cabal/users-guide/
--
-- The name of the package.
name:               day-2

-- The package version.
-- See the Haskell package versioning policy (PVP) for standards
-- guiding when and how versions should be incremented.
-- https://pvp.haskell.org
-- PVP summary:     +-+------- breaking API changes
--                  | | +----- non-breaking API additions
--                  | | | +--- code changes with no API change
version:            0.1.0.0

-- A short (one-line) description of the package.
-- synopsis:

-- A longer description of the package.
-- description:

-- The license under which the package is released.
license:            AGPL-3.0-or-later

-- The file containing the license text.
license-file:       LICENSE

-- The package author(s).
author:             <redacted>

-- An email address to which users can send suggestions, bug reports, and patches.
maintainer:         <redacted>

-- A copyright notice.
-- copyright:
build-type:         Simple

-- Extra doc files to be distributed with the package, such as a CHANGELOG or a README.
extra-doc-files:    CHANGELOG.md

-- Extra source files to be distributed with the package, such as examples, or a tutorial module.
-- extra-source-files:

common warnings
    ghc-options: -Wall

executable day-2
    -- Import common warning flags.
    import:           warnings

    -- .hs or .lhs file containing the Main module.
    main-is:          Main.hs

    -- Modules included in this executable, other than Main.
    -- other-modules:

    -- LANGUAGE extensions used by modules in this package.
    -- other-extensions:

    -- Other library packages from which modules are imported.
    build-depends:    base ^>=4.12.0.0

    -- Directories containing source files.
    hs-source-dirs:   app

    -- Base language which the package is written in.
    default-language: Haskell2010

下面是它创建的文件列表：

$ find . -type f
./app/Main.hs
./LICENSE
./CHANGELOG.md
./day-2.cabal
./dist-newstyle/cache/compiler
./README.md # I created this one myself, manually

我去编译了我的app/Main.hs文件，该文件如下所示：

module Main where

main :: IO ()
main = putStrLn "hello"

当我运行cabal build时，会得到以下错误：

$ cabal build
Errors encountered when parsing cabal file ./day-2.cabal:

day-2.cabal:14:26: error:
unexpected end of input

    1 | cabal-version:      3.4
    2 | -- The cabal-version field refers to the version of the .cabal specification,
    3 | -- and can be different from the cabal-install (the tool) version and the
    4 | -- Cabal (the library) version you are using. As such, the Cabal (the library)
    5 | -- version used must be equal or greater than the version stated in this field.
    6 | -- Starting from the specification version 2.2, the cabal-version field must be
    7 | -- the first thing in the cabal file.
    8 | 
    9 | -- Initial package description 'day-2' generated by
   10 | -- 'cabal init'. For further documentation, see:
   11 | --   http://haskell.org/cabal/users-guide/
   12 | --
   13 | -- The name of the package.
   14 | name:               day-2
      |                          ^

我没看到其他人在谈论这个特别的问题。

这是我的阴谋版本：

$ cabal --version
cabal-install version 3.8.1.0
compiled using version 3.8.1.0 of the Cabal library 

不确定是否相关，但这也是我的ghc版本：

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.6.5

我应该说，昨天我在一个不同的目录下运行了cabal init (对于第1天)，它使我的Main.hs和day-1.cabal文件变得很好，并且它能够构建和运行而没有问题。

不知道问题出在哪里，希望有人知道出了什么问题。

Answer 1

包名可能包含字母、数字和连字符，但不包含空格，也可能不包含仅由数字组成的连字符部分。 https://cabal.readthedocs.io/en/stable/developing-packages.html#package-names-and-versions

否则，语法$PACKAGE-$VERSION将是模糊的。