Use simplified lvar

ema-examples/ema-examples.cabal

@@ -87,7 +87,7 @@ library
     , generic-optics
     , generics-sop
     , http-types
-    , lvar
+    , lvar                    >=0.2
     , monad-logger
     , monad-logger-extras
     , mtl

ema/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased (0.10.4.0)
 
 - Relax `base` constraint forever
+- Require `lvar` 0.2 or later ([simplified API](https://github.com/srid/lvar/pull/8))
 - API changes
   - `Ema.CLI`: The `Action` type is no longer a GADT.
   - `Ema.Server`: This module has be split into several smaller modules

ema/ema.cabal

@@ -86,7 +86,7 @@ library
     , filepath
     , filepattern
     , http-types
-    , lvar
+    , lvar                   >=0.2
     , monad-logger
     , monad-logger-extras
     , mtl

ema/src/Ema/Server/WebSocket.hs

@@ -17,7 +17,6 @@ import Ema.Site (EmaStaticSite)
 import Network.WebSockets (ConnectionException)
 import Network.WebSockets qualified as WS
 import Optics.Core (review)
-import Text.Printf (printf)
 import UnliftIO.Async (race)
 import UnliftIO.Exception (try)
 
@@ -32,9 +31,8 @@ wsApp ::
 wsApp logger model emaWsHandler pendingConn = do
   conn :: WS.Connection <- WS.acceptRequest pendingConn
   WS.withPingThread conn 30 pass . flip runLoggingT logger $ do
-    subId <- LVar.addListener model
     let log lvl (s :: Text) =
-          logWithoutLoc (toText @String $ printf "ema.ws.%.2d" subId) lvl s
+          logWithoutLoc "ema.ws" lvl s
     log LevelInfo "Connected"
     let wsHandler = unEmaWsHandler emaWsHandler conn
         sendRouteHtmlToClient path s = do
@@ -60,7 +58,7 @@ wsApp logger model emaWsHandler pendingConn = do
           -- Listen *until* either we get a new value, or the client requests
           -- to switch to a new route.
           currentModel <- LVar.get model
-          race (LVar.listenNext model subId) (wsHandler currentModel) >>= \case
+          race (LVar.listenNext model) (wsHandler currentModel) >>= \case
             Left newModel -> do
               -- The page the user is currently viewing has changed. Send
               -- the new HTML to them.
@@ -83,4 +81,3 @@ wsApp logger model emaWsHandler pendingConn = do
             log LevelInfo $ "Closing websocket connection (reason: " <> reason <> ")"
           _ ->
             log LevelError $ "Websocket error: " <> show connExc
-        LVar.removeListener model subId

flake.nix

@@ -8,6 +8,9 @@
     git-hooks.url = "github:cachix/git-hooks.nix";
     git-hooks.flake = false;
     emanote.url = "github:srid/emanote";
+
+    lvar.url = "github:srid/lvar";
+    lvar.flake = false;
   };
   outputs = inputs@{ self, nixpkgs, flake-parts, ... }:
     flake-parts.lib.mkFlake { inherit inputs; } {
@@ -22,6 +25,7 @@
         # This attr is provided by https://github.com/srid/haskell-flake
         haskellProjects.default = {
           autoWire = [ "packages" "checks" ];
+          packages.lvar.source = inputs.lvar;
         };
 
         devShells.default = pkgs.mkShell {