vscode-haskell

Toolchain 選擇

在 .vscode/settings.json 中使用 haskell.toolchain 選擇指定版本。

{
    "haskell.toolchain": {
        "hls": "2.2.0.0",
        "cabal": "3.10.1.0",
        "stack": "2.11.1"
    }
}

formatter 選擇

floskell, ^config

LSP - Language Server Protocol

• Client: vscode-haskell ( vscode-languageclient )
• Server: haskell-language-server ( lsp, hls-graph, ghcide, hls-plugin, hie-bios, hiedb , GHC, ... )

遇到問題，不妨重啟試試。

• hie-bios 目前優先設定為隱式發現。
• Multi Cradle: No prefixes matched, 先不關注
• Loading the module 'foo.hs' failed, 聽從提示
• !!MISSING: command!!, 等等看

GHCi

Multi line

GHCi 里使用 :{ ... :}或使用 :set +m.

Loading a multi-module program

在 .hs 所在目錄，GHCi 里使用 :load Main，會根據 impdecls 查找 import 項。

GHC Package environments

A package environment file is a file that tells ghc precisely which packages should be visible. 

控制某包是否可見，如某包不可見，GHC/GHCi 處理時會顯示類似于It is a member of the hidden package 'base-4.17.2.0', 需要設置為可見。

-hide-all-packages, This is a good way to insulate your program from differences in the globally exposed packages, and being explicit about package dependencies is a Good Thing.

Cabal always passes the -hide-all-packages flag to GHC, for exactly this reason.

GHC/GHCi 會默認加載當前目錄（及父目錄）下的 package environment file, 其次全局；選項-package-env <file>指定加載.

Cabal ( cabal-install )

proj.cabal

先關注 other-modules 和 build-depends 項，其他項有更多需求再關注。

other-modules

For an executable, other modules included in the executable should be listed in the other-modules field.

build-depends

Instead, you add the package you want to use to the build-depends section of the .cabal file of your package.

Cabal will take care of fetching and building the dependency as needed when you run cabal build, cabal run, or other similar commands.

Cabal 項目中，在 build-depends添加依賴庫名稱，Cabal 會處理的。

Adding libraries to GHC package environments

cabal install --lib, 默認為全局,%APPDATA%/ghc/$ARCH-$OS-$GHCVER/environments/default.

cabal install --package-env 配合使用，確定使用哪個. 

更多

• 2022 State of Haskell Survey Results - <https://taylor.fausak.me/2022/11/18/haskell-survey-results/>
• 「Haskell に IDE はないのか？──獨斷と偏見による Haskell の IDE 十年史」 - <https://zenn.dev/konn/articles/1a60baba9848a1>
• Mitchell, N., Kiefer, M., Iborra, P., Lau, L., Duggal, Z., Siebenhandl, H., Sanchez, J. N., Pickering, M., & Zimmerman, A. Building an Integrated Development Environment (IDE) on top of a Build System: The tale of a Haskell IDE. Proceedings of the 32nd Symposium on Implementation and Application of Functional Languages, 1–10. 2020. https://doi.org/10.1145/3462172.3462180

• https://cabal.readthedocs.io/en/3.10/developing-packages.html#modules-included-in-the-package
• https://downloads.haskell.org/ghc/latest/docs/users_guide/packages.html#package-environments
• https://cabal.readthedocs.io/en/3.10/cabal-commands.html#cabal-install
• Separate cabal install --lib into own command (cabal env)  - <https://github.com/haskell/cabal/issues/6481>

• Improve the error message for unknown modules - <https://github.com/haskell/haskell-language-server/issues/3695>
• 2021 How to get VSCode to recognize a dependency - <https://github.com/tomjaguarpaw/tilapia/issues/93>
• HLS 2.3.0.0 release possibly borked on Windows - <https://github.com/haskell/haskell-language-server/issues/3822>