hot reload for elm application

Makefile

@@ -40,12 +40,9 @@ backend:
 
 serve: frontend backend
 ifeq ($(DEBUG),1)
-	RUST_LOG=info,actix_web=debug $(CARGO_RUN) --manifest-path=$(BACKEND_DIR)/Cargo.toml
+	$(MAKE) -C $(FRONTEND_DIR) serve DEBUG=1 & \
+	RUST_LOG=info,actix_web=debug $(CARGO_RUN) --manifest-path=$(BACKEND_DIR)/Cargo.toml; \
+	kill %1
 else ifeq ($(RELEASE),1)
 	$(CARGO_RUN) --release --manifest-path=$(BACKEND_DIR)/Cargo.toml
 endif
-
-clean:
-	rm -rf $(PUBLIC_DIR)/*
-	rm -rf $(BACKEND_DIR)/target
-	make -C $(FRONTEND_DIR) clean

README.md

@@ -12,6 +12,13 @@ make serve RELEASE=1 # can also do DEBUG=1 instead
 
 Now open `http://127.0.0.1:8080` in your browser.
 
+# Elm application hot reloading
+
+Hot reloading for Elm application is exposed at port `8000` under `DEBUG=1` mode.
+
+`make serve DEBUG=1`
+visit `localhost:8000`
+
 # TODO
 
- - [ ] Address compiler warnings.
+ - [ ] Address compiler warnings.

flake.nix

@@ -113,6 +113,19 @@
           with pkgs;
           mkShell {
             inputsFrom = [ example-spa-elm-app ];
+            buildInputs = [
+              nodejs_22
+             ];
+
+             shellHook = ''
+               if [ ! -d "$PWD/frontend/node_modules/elm-go" ]; then
+                 echo "Installing elm-go..."
+                 cd "$PWD/frontend"
+                 ${nodejs_22}/bin/npm install elm-go
+                 cd ..
+               fi
+               export PATH="$PWD/frontend/node_modules/.bin:$PATH"
+             '';
           };
       }
     );

frontend/Makefile

@@ -2,7 +2,7 @@ SRC_FILES := $(shell find src -name "*.elm")
 
 all: elm.min.js
 
-.PHONY: elm.min.js
+.PHONY: elm.min.js serve
 
 ifeq ($(DEBUG)$(RELEASE),) # Both are empty
 $(error You must set exactly one of DEBUG=1 or RELEASE=1)
@@ -12,7 +12,6 @@ ifeq ($(DEBUG)$(RELEASE),11) # Both are set
 $(error Both DEBUG and RELEASE cannot be set at the same time)
 endif
 
-
 elm.min.js:
 ifeq ($(DEBUG),1)
 	./build.sh --debug src/Main.elm
@@ -20,5 +19,12 @@ else ifeq ($(RELEASE),1)
 	./build.sh --optimize src/Main.elm
 endif
 
+serve:
+ifeq ($(DEBUG),1)
+	elm-go src/Main.elm --port=8000 --dir=../public --start-page=index.html -- --output=../public/elm.min.js
+else ifeq ($(RELEASE),1)
+	$(error Cannot use serve target with RELEASE=1)
+endif
+
 clean:
 	rm elm.js elm.min.js