phoityne-vscode: Haskell Debug Adapter for Visual Studio Code.

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Dependencies aeson, base (>=4.7 && <5), bytestring, Cabal, cmdargs, conduit, conduit-extra, containers, data-default, directory, filepath, fsnotify, hslogger, lens, MissingH, mtl, parsec, process, resourcet, safe, safe-exceptions, split, text, transformers [details]
License BSD-3-Clause
Copyright 2016-2018 phoityne_hs
Author phoityne_hs
Category Development
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Uploaded by phoityne_hs at Fri Aug 3 21:51:50 UTC 2018
Distributions NixOS:
Executables phoityne-vscode
Downloads 4137 total (51 in the last 30 days)
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Status Docs not available [build log]
Last success reported on 2018-08-03 [all 3 reports]
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Phoityne VSCode

Phoityne is a Haskell GHCi debug adapter for Visual Studio Code.


(This sample project is available from here.)


  • LIMITATION: Source file extension must be ".hs"
  • LIMITATION: Can not use STDIN handle while debugging.
  • When you start debugging for the first time, .vscode/tasks.json will be created automatically. Then you can use F6, F7, F8 shortcut key.
    • F5 : start debug
    • F6 : show command menu (for stack watch)
    • Shift + F6 : stop stack watch
    • F7 : stack clean & build
    • F8 : stack test
    • F9 : put bp on current line
    • Shift + F9 : put bp on current column
  • While debugging, you can use F5, F9, F10, F11 shortcut key.
    • F5 : jump to next bp
    • F9 : put bp on the line
    • Shift + F9 : put bp on the column
    • F10 : step next
    • F11 : step into


Run to Cursor


Bindings & Watch

The variable added to watch will be forced.


Stack trace


Break condition


Hit count break condition

Supports these operators.

  • /=
  • <, >
  • <=, >=
  • mod, %
  • just digit is same with '>='


Break on Exception


Repl & Completions


and more

Better inspection. This is an experimental enhancement.
There are limitations and additional installation.
Here are the details.



  • supportsConfigurationDoneRequest : yes
  • supportsFunctionBreakpoints : yes
  • supportsConditionalBreakpoints : yes
  • supportsHitConditionalBreakpoints : yes
  • supportsEvaluateForHovers : yes
  • exceptionBreakpointFilters : yes
  • supportsStepBack : no
  • supportsSetVariable : no
  • supportsRestartFrame : no
  • supportsGotoTargetsRequest : no
  • supportsStepInTargetsRequest : no
  • supportsCompletionsRequest : yes
  • supportsModulesRequest : no
  • additionalModuleColumns : no
  • supportedChecksumAlgorithms : no
  • supportsRestartRequest : no
  • supportsExceptionOptions : no
  • supportsValueFormattingOptions : no
  • supportsExceptionInfoRequest : no
  • supportTerminateDebuggee : no
  • supportsDelayedStackTraceLoading : no
  • supportsLogPoints : yes (by haskell-dap)


Run stack install

% stack install phoityne-vscode
  . . . . .

Add 'phoityne-vscode.exe' to PATH environment.


% where $path:phoityne-vscode.exe
C:\Users\[user name]\AppData\Roaming\local\bin\phoityne-vscode.exe

% phoityne-vscode --version
% code


$ which phoityne-vscode
$ phoityne-vscode --version
$ code

Install vscode extensions

  1. run VSCode and open stack project Folder from file menu.
  2. open Extensions from side menu of VSCode.
  3. search "haskell"
  4. select "Haskell GHCi debug adapter Phoityne"



|NAME|REQUIRED OR OPTIONAL|DEFAULT SETTING|DESCRIPTION| |:--|:--:|:--|:--| |startup|required|${workspaceRoot}/test/Spec.hs|debug startup file, will be loaded automatically.| |startupFunc|optional|"" (empty string)|debug startup function, will be run instead of main function.| |startupArgs|optional|"" (empty string)|arguments for startup function. set as string type.| |ghciCmd|required|stack ghci --test --no-load --no-build --main-is TARGET --ghci-options -fprint-evld-with-show|launch ghci command, must be Prelude module loaded. For example, "ghci -i${workspaceRoot}/src", "cabal exec -- ghci -i${workspaceRoot}/src"| |ghciPrompt|required|H>>=|ghci command prompt string.| |ghciInitialPrompt|optional|"Prelude> "|initial pormpt of ghci. set it when using custom prompt. e.g. set in .ghci| |stopOnEntry|required|true|stop or not after debugger launched. |mainArgs|optional|"" (empty string)|main arguments.| |logFile|required|${workspaceRoot}/.vscode/phoityne.log|internal log file.| |logLevel|required|WARNING|internal log level.|

changing ghci initial prompt

If you change ghci prompt in .ghci file, or ghci prompt is changed from "Prelude>" by applying NoImplicitPrelude extension, set the initial prompt variable to same prompt string.

% diff .vscode/launch.json.old .vscode/launch.json
<             "ghciInitialPrompt": "Prelude> "      // default value.
>             "ghciInitialPrompt": "> "             // e.g.

Make sure needs of the last space, and don't forget adding it.

setting the startup hs file

Set the startup variable to the path of .hs file in which main function is defined.

% diff .vscode/launch.json.old .vscode/launch.json
<             "startup": "${workspaceRoot}/test/Spec.hs",    // default value.
>             "startup": "${workspaceRoot}/app/run.hs",     // e.g.

setting the startup function

If you want to run the specific function instead of main function, set the startupFunc variable.
For example, when specifying the following startDebug function,

startDebug :: String -> IO ()
startDebug name = do
  putStrLn "hello"
  putStrLn name 

set the valiavles in the launch.json file.

% diff .vscode/launch.json.old .vscode/launch.json
<             "startupFunc": "",    // default value.
<             "startupArgs": "",    // default value.
>             "startupFunc": "startDebug",       // e.g.
>             "startupArgs": "\"phoityne\"",     // e.g.

changing log level

For debuging phoityen itself, change the log level to DEBUG.
Adding Issue with the debug log.

% diff .vscode/launch.json.old .vscode/launch.json
<             "logLevel": "WARNING",               // default value.
>             "logLevel": "DEBUG",                 // e.g.


|TASK NAME|REQUIRED OR OPTIONAL|DEFAULT SETTING|DESCRIPTION| |:--|:--:|:--|:--| |stack build|required|stack build|task definition for F6 shortcut key.| |stack clean & build|required|stack clean && stack build|task definition for F7 shortcut key.| |stack test|required|stack test|task definition for F8 shortcut key.| |stack watch|required|stack build --test --no-run-tests --file-watch|task definition for F6 shortcut key.|