Use CPS Writer Monad

default.nix

@@ -1,9 +1,9 @@
 { mkDerivation, ansi-terminal, async, attoparsec, base, bytestring
 , cassava, containers, data-default, directory, extra, filepath
-, hermes-json, HUnit, lib, lock-file, MemoTrie, mtl, nix-derivation
+, hermes-json, HUnit, lib, lock-file, MemoTrie, nix-derivation
 , optics, random, relude, safe, stm, streamly-core, strict
-, strict-types, terminal-size, text, time, typed-process, unix
-, word8
+, strict-types, terminal-size, text, time, transformers
+, typed-process, unix, word8
 }:
 mkDerivation {
   pname = "nix-output-monitor";
@@ -14,21 +14,21 @@ mkDerivation {
   libraryHaskellDepends = [
     ansi-terminal async attoparsec base bytestring cassava containers
     data-default directory extra filepath hermes-json lock-file
-    MemoTrie mtl nix-derivation optics relude safe stm streamly-core
-    strict strict-types terminal-size text time word8
+    MemoTrie nix-derivation optics relude safe stm streamly-core strict
+    strict-types terminal-size text time transformers word8
   ];
   executableHaskellDepends = [
     ansi-terminal async attoparsec base bytestring cassava containers
     data-default directory extra filepath hermes-json lock-file
-    MemoTrie mtl nix-derivation optics relude safe stm streamly-core
-    strict strict-types terminal-size text time typed-process unix
-    word8
+    MemoTrie nix-derivation optics relude safe stm streamly-core strict
+    strict-types terminal-size text time transformers typed-process
+    unix word8
   ];
   testHaskellDepends = [
     ansi-terminal async attoparsec base bytestring cassava containers
     data-default directory extra filepath hermes-json HUnit lock-file
-    MemoTrie mtl nix-derivation optics random relude safe stm
-    streamly-core strict strict-types terminal-size text time
+    MemoTrie nix-derivation optics random relude safe stm streamly-core
+    strict strict-types terminal-size text time transformers
     typed-process word8
   ];
   homepage = "https://github.com/maralorn/nix-output-monitor";

exe/Main.hs

@@ -2,7 +2,7 @@ module Main (main) where
 
 import Control.Concurrent (ThreadId, myThreadId, throwTo)
 import Control.Exception qualified as Exception
-import Control.Monad.Writer.Strict (WriterT (runWriterT))
+import Control.Monad.Trans.Writer.CPS (runWriterT)
 import Data.ByteString qualified as ByteString
 import Data.IORef qualified as IORef
 import Data.Text.IO (hPutStrLn)

lib/NOM/Update.hs

@@ -1,7 +1,6 @@
 module NOM.Update (updateStateNixJSONMessage, updateStateNixOldStyleMessage, maintainState, detectLocalFinishedBuilds, appendDifferingPlatform) where
 
-import Control.Monad.Writer (MonadWriter (tell))
-import Control.Monad.Writer.Strict (WriterT (runWriterT))
+import Control.Monad.Trans.Writer.CPS (WriterT, runWriterT, tell)
 import Data.ByteString.Char8 qualified as ByteString
 import Data.IntMap.Strict qualified as IntMap
 import Data.Map.Strict qualified as Map

lib/NOM/Update/Monad.hs

@@ -1,3 +1,6 @@
+{-# LANGUAGE UndecidableInstances #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+
 module NOM.Update.Monad (
   UpdateMonad,
   MonadNow (..),
@@ -7,16 +10,15 @@ module NOM.Update.Monad (
 ) where
 
 import Control.Exception (try)
-import Control.Monad.Writer.Strict (WriterT)
+import Control.Monad.Trans.Writer.CPS (WriterT)
 -- attoparsec
 import Data.Attoparsec.Text (eitherResult, parse)
 import Data.Text.IO qualified as TextIO
--- nix-derivation
-
 import GHC.Clock qualified
 import NOM.Builds (Derivation, StorePath)
 import NOM.Error (NOMError (..))
 import NOM.Update.Monad.CacheBuildReports
+-- nix-derivation
 import Nix.Derivation qualified as Nix
 import Relude
 import System.Directory (doesPathExist)
@@ -32,7 +34,7 @@ instance MonadNow IO where
 instance (MonadNow m) => MonadNow (StateT a m) where
   getNow = lift getNow
 
-instance (Monoid a, MonadNow m) => MonadNow (WriterT a m) where
+instance (MonadNow m) => MonadNow (WriterT a m) where
   getNow = lift getNow
 
 class (Monad m) => MonadReadDerivation m where
@@ -56,7 +58,7 @@ instance (MonadReadDerivation m) => MonadReadDerivation (StateT a m) where
 instance (MonadReadDerivation m) => MonadReadDerivation (ExceptT a m) where
   getDerivation = lift . getDerivation
 
-instance (Monoid a, MonadReadDerivation m) => MonadReadDerivation (WriterT a m) where
+instance (MonadReadDerivation m) => MonadReadDerivation (WriterT a m) where
   getDerivation = lift . getDerivation
 
 class (Monad m) => MonadCheckStorePath m where
@@ -68,5 +70,10 @@ instance MonadCheckStorePath IO where
 instance (MonadCheckStorePath m) => MonadCheckStorePath (StateT a m) where
   storePathExists = lift . storePathExists
 
-instance (Monoid a, MonadCheckStorePath m) => MonadCheckStorePath (WriterT a m) where
+instance (MonadCheckStorePath m) => MonadCheckStorePath (WriterT a m) where
   storePathExists = lift . storePathExists
+
+instance (MonadState s m) => MonadState s (WriterT w m) where
+  get = lift get
+  put = lift . put
+  state = lift . state

lib/NOM/Update/Monad/CacheBuildReports.hs

@@ -7,7 +7,7 @@ module NOM.Update.Monad.CacheBuildReports (
 ) where
 
 import Control.Exception (IOException, catch)
-import Control.Monad.Writer.Strict (WriterT)
+import Control.Monad.Trans.Writer.CPS (WriterT)
 -- cassava
 import Data.Csv (FromRecord, HasHeader (NoHeader), ToRecord, decode, encode)
 -- data-default
@@ -55,7 +55,7 @@ instance (MonadCacheBuildReports m) => MonadCacheBuildReports (StateT a m) where
   getCachedBuildReports = lift getCachedBuildReports
   updateBuildReports = lift . updateBuildReports
 
-instance (Monoid a, MonadCacheBuildReports m) => MonadCacheBuildReports (WriterT a m) where
+instance (MonadCacheBuildReports m) => MonadCacheBuildReports (WriterT a m) where
   getCachedBuildReports = lift getCachedBuildReports
   updateBuildReports = lift . updateBuildReports
 

nix-output-monitor.cabal

@@ -72,7 +72,6 @@ common common-config
     , hermes-json     >=0.6.0.0
     , lock-file
     , MemoTrie
-    , mtl
     , nix-derivation
     , optics
     , relude
@@ -84,6 +83,7 @@ common common-config
     , terminal-size
     , text
     , time
+    , transformers
     , word8
 
   default-language:   GHC2021

test/Golden.hs

@@ -1,6 +1,6 @@
 module Main (main) where
 
-import Control.Monad.Writer.Strict (WriterT (runWriterT))
+import Control.Monad.Trans.Writer.CPS (runWriterT)
 import Data.ByteString.Char8 qualified as ByteString
 import Data.Text qualified as Text
 import NOM.Builds (parseStorePath)