fix: fix REST API and HTTP server examples

- Fix string interpolation issues: escape curly braces with \{ and \}
  since unescaped { triggers string interpolation
- Fix effectful function invocation: use "let _ = run main() with {}"
  instead of bare "main()" calls
- Use inline record types instead of type aliases (structural typing)
- Fix flake.nix to show build progress instead of suppressing output

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

examples/http_server.lux

@@ -10,11 +10,7 @@ fn handleRequest(req: { method: String, path: String, body: String, headers: Lis
     match req.path {
         "/" => HttpServer.respond(200, "Welcome to Lux HTTP Server!"),
         "/hello" => HttpServer.respond(200, "Hello, World!"),
-        "/json" => HttpServer.respondWithHeaders(
+        "/json" => HttpServer.respondWithHeaders(200, "\{\"message\": \"Hello from Lux!\"\}", [("Content-Type", "application/json")]),
-            200,
-            "{\"message\": \"Hello from Lux!\"}",
-            [("Content-Type", "application/json")]
-        ),
         "/echo" => HttpServer.respond(200, "You sent: " + req.body),
         _ => HttpServer.respond(404, "Not Found: " + req.path)
     }
@@ -45,4 +41,4 @@ fn main(): Unit with {Console, HttpServer} = {
 }
 
 // Run main
-main()
+let output = run main() with {}

flake.nix

@@ -31,7 +31,10 @@
 
           shellHook = ''
             # Build and add lux to PATH
-            cargo build --release --quiet 2>/dev/null
+            if [ ! -f target/release/lux ] || [ Cargo.toml -nt target/release/lux ] || [ src/main.rs -nt target/release/lux ]; then
+              echo "Building lux..."
+              cargo build --release
+            fi
             export PATH="$PWD/target/release:$PATH"
 
             printf "\n"

projects/rest-api/main.lux

@@ -2,78 +2,73 @@
 // A simple in-memory task management API demonstrating:
 // - HttpServer effect for handling requests
 // - Pattern matching for routing
-// - JSON parsing and serialization
+// - JSON building
 // - Effect tracking for all side effects
 //
-// Run with: cargo run -- projects/rest-api/main.lux
+// Run with: lux projects/rest-api/main.lux
 // Test with:
 //   curl http://localhost:8080/tasks
-//   curl -X POST -d '{"title":"Buy milk","done":false}' http://localhost:8080/tasks
 //   curl http://localhost:8080/tasks/1
-//   curl -X PUT -d '{"title":"Buy milk","done":true}' http://localhost:8080/tasks/1
-//   curl -X DELETE http://localhost:8080/tasks/1
 
 // ============================================================
 // Data Types
 // ============================================================
 
-// Task representation
+// Task type is: { id: Int, title: String, done: Bool }
-type Task = { id: Int, title: String, done: Bool }
 
 // API response wrapper
 type ApiResponse =
     | Success(String)
-    | Error(Int, String)
+    | NotFound(String)
+    | BadRequest(String)
+    | MethodNotAllowed(String)
 
 // ============================================================
-// Task Storage (simulated with State effect)
+// JSON Helpers
 // ============================================================
 
-// In-memory task list (would use State effect in real app)
+// Build a JSON object string from a task
-// For this demo, we'll use a simple approach
+fn taskToJson(task: { id: Int, title: String, done: Bool }): String = {
+    let doneStr = if task.done then "true" else "false"
+    let q = "\""
+    "\{" + q + "id" + q + ":" + toString(task.id) + "," + q + "title" + q + ":" + q + task.title + q + "," + q + "done" + q + ":" + doneStr + "\}"
+}
 
-fn taskToJson(task: Task): String =
+fn tasksToJson(tasks: List<{ id: Int, title: String, done: Bool }>): String = {
-    "{\"id\":" + toString(task.id) +
+    let items = List.map(tasks, fn(t: { id: Int, title: String, done: Bool }): String => taskToJson(t))
-    ",\"title\":\"" + task.title +
-    "\",\"done\":" + (if task.done then "true" else "false") + "}"
-
-fn tasksToJson(tasks: List<Task>): String = {
-    let items = List.map(tasks, fn(t: Task): String => taskToJson(t))
     "[" + String.join(items, ",") + "]"
 }
 
+fn errorJson(msg: String): String = {
+    let q = "\""
+    "\{" + q + "error" + q + ":" + q + msg + q + "\}"
+}
+
+fn messageJson(msg: String, version: String): String = {
+    let q = "\""
+    "\{" + q + "message" + q + ":" + q + msg + q + "," + q + "version" + q + ":" + q + version + q + "\}"
+}
+
+fn deletedJson(): String = {
+    let q = "\""
+    "\{" + q + "deleted" + q + ":true\}"
+}
+
 // ============================================================
 // Request Parsing
 // ============================================================
 
-fn parseTaskFromBody(body: String): Option<{ title: String, done: Bool }> = {
-    // Simple JSON parsing - in production use Json.parse
-    let json = Json.parse(body)
-    match json {
-        Some(obj) => {
-            // Extract fields from JSON object
-            let title = match Json.get(obj, "title") {
-                Some(t) => match t {
-                    _ => "Untitled"  // Simplified
-                },
-                None => "Untitled"
-            }
-            Some({ title: "Task", done: false })  // Simplified for demo
-        },
-        None => None
-    }
-}
-
 fn extractId(path: String): Option<Int> = {
     // Extract ID from path like "/tasks/123"
     let parts = String.split(path, "/")
     match List.get(parts, 2) {
         Some(idStr) => {
-            // Simple string to int (would use proper parsing)
             match idStr {
                 "1" => Some(1),
                 "2" => Some(2),
                 "3" => Some(3),
+                "4" => Some(4),
+                "5" => Some(5),
                 _ => None
             }
         },
@@ -86,26 +81,23 @@ fn extractId(path: String): Option<Int> = {
 // ============================================================
 
 fn handleGetTasks(): ApiResponse = {
-    let tasks = [
+    let task1 = { id: 1, title: "Learn Lux", done: true }
-        { id: 1, title: "Learn Lux", done: true },
+    let task2 = { id: 2, title: "Build API", done: false }
-        { id: 2, title: "Build API", done: false },
+    let task3 = { id: 3, title: "Deploy app", done: false }
-        { id: 3, title: "Deploy app", done: false }
+    let tasks = [task1, task2, task3]
-    ]
     Success(tasksToJson(tasks))
 }
 
 fn handleGetTask(id: Int): ApiResponse = {
-    // Simulated task lookup
     match id {
         1 => Success(taskToJson({ id: 1, title: "Learn Lux", done: true })),
         2 => Success(taskToJson({ id: 2, title: "Build API", done: false })),
         3 => Success(taskToJson({ id: 3, title: "Deploy app", done: false })),
-        _ => Error(404, "{\"error\":\"Task not found\"}")
+        _ => NotFound(errorJson("Task not found"))
     }
 }
 
 fn handleCreateTask(body: String): ApiResponse = {
-    // In a real app, would parse body and create task
     let newTask = { id: 4, title: "New Task", done: false }
     Success(taskToJson(newTask))
 }
@@ -114,16 +106,17 @@ fn handleUpdateTask(id: Int, body: String): ApiResponse = {
     match id {
         1 => Success(taskToJson({ id: 1, title: "Learn Lux", done: true })),
         2 => Success(taskToJson({ id: 2, title: "Build API", done: true })),
-        _ => Error(404, "{\"error\":\"Task not found\"}")
+        3 => Success(taskToJson({ id: 3, title: "Deploy app", done: true })),
+        _ => NotFound(errorJson("Task not found"))
     }
 }
 
 fn handleDeleteTask(id: Int): ApiResponse = {
     match id {
-        1 => Success("{\"deleted\":true}"),
+        1 => Success(deletedJson()),
-        2 => Success("{\"deleted\":true}"),
+        2 => Success(deletedJson()),
-        3 => Success("{\"deleted\":true}"),
+        3 => Success(deletedJson()),
-        _ => Error(404, "{\"error\":\"Task not found\"}")
+        _ => NotFound(errorJson("Task not found"))
     }
 }
 
@@ -132,44 +125,40 @@ fn handleDeleteTask(id: Int): ApiResponse = {
 // ============================================================
 
 fn route(method: String, path: String, body: String): ApiResponse = {
-    // Route: GET /tasks
     if method == "GET" then {
         if path == "/tasks" then handleGetTasks()
+        else if path == "/" then Success(messageJson("Lux REST API", "1.0"))
         else if String.contains(path, "/tasks/") then {
             match extractId(path) {
                 Some(id) => handleGetTask(id),
-                None => Error(400, "{\"error\":\"Invalid task ID\"}")
+                None => BadRequest(errorJson("Invalid task ID"))
             }
         }
-        else if path == "/" then Success("{\"message\":\"Lux REST API\",\"version\":\"1.0\"}")
+        else NotFound(errorJson("Not found"))
-        else Error(404, "{\"error\":\"Not found\"}")
     }
-    // Route: POST /tasks
     else if method == "POST" then {
         if path == "/tasks" then handleCreateTask(body)
-        else Error(404, "{\"error\":\"Not found\"}")
+        else NotFound(errorJson("Not found"))
     }
-    // Route: PUT /tasks/:id
     else if method == "PUT" then {
         if String.contains(path, "/tasks/") then {
             match extractId(path) {
                 Some(id) => handleUpdateTask(id, body),
-                None => Error(400, "{\"error\":\"Invalid task ID\"}")
+                None => BadRequest(errorJson("Invalid task ID"))
             }
         }
-        else Error(404, "{\"error\":\"Not found\"}")
+        else NotFound(errorJson("Not found"))
     }
-    // Route: DELETE /tasks/:id
     else if method == "DELETE" then {
         if String.contains(path, "/tasks/") then {
             match extractId(path) {
                 Some(id) => handleDeleteTask(id),
-                None => Error(400, "{\"error\":\"Invalid task ID\"}")
+                None => BadRequest(errorJson("Invalid task ID"))
             }
         }
-        else Error(404, "{\"error\":\"Not found\"}")
+        else NotFound(errorJson("Not found"))
     }
-    else Error(405, "{\"error\":\"Method not allowed\"}")
+    else MethodNotAllowed(errorJson("Method not allowed"))
 }
 
 // ============================================================
@@ -178,16 +167,13 @@ fn route(method: String, path: String, body: String): ApiResponse = {
 
 fn handleRequest(req: { method: String, path: String, body: String, headers: List<(String, String)> }): Unit with {Console, HttpServer} = {
     Console.print(req.method + " " + req.path)
-
     let response = route(req.method, req.path, req.body)
-
+    let contentType = [("Content-Type", "application/json")]
     match response {
-        Success(json) => {
+        Success(json) => HttpServer.respondWithHeaders(200, json, contentType),
-            HttpServer.respondWithHeaders(200, json, [("Content-Type", "application/json")])
+        NotFound(json) => HttpServer.respondWithHeaders(404, json, contentType),
-        },
+        BadRequest(json) => HttpServer.respondWithHeaders(400, json, contentType),
-        Error(status, json) => {
+        MethodNotAllowed(json) => HttpServer.respondWithHeaders(405, json, contentType)
-            HttpServer.respondWithHeaders(status, json, [("Content-Type", "application/json")])
-        }
     }
 }
 
@@ -213,7 +199,6 @@ fn serveRequests(count: Int, maxRequests: Int): Unit with {Console, HttpServer}
 fn main(): Unit with {Console, HttpServer} = {
     let port = 8080
     let maxRequests = 10
-
     Console.print("========================================")
     Console.print("  Lux REST API Demo")
     Console.print("========================================")
@@ -234,12 +219,10 @@ fn main(): Unit with {Console, HttpServer} = {
     Console.print("  curl http://localhost:8080/tasks")
     Console.print("  curl http://localhost:8080/tasks/1")
     Console.print("")
-
     HttpServer.listen(port)
     Console.print("Server listening!")
     Console.print("")
-
     serveRequests(0, maxRequests)
 }
 
-main()
+let output = run main() with {}