From 30a68209fbec7fc6a0b7aed1e9a5d277d9424e11 Mon Sep 17 00:00:00 2001
From: Carl Worth <cworth@cworth.org>
Date: Fri, 23 Dec 2022 11:49:29 -0800
Subject: [PATCH] Make any code execution errors visible to the users

By sending them to the clients and having them render it in red
monospace with pre-wrapped whitespace.

This should allow the players to debug things when they don't work.
---
 bus.html | 15 ++++++++++++++-
 index.js |  3 ++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/bus.html b/bus.html
index 5760786..40e50d3 100644
--- a/bus.html
+++ b/bus.html
@@ -94,6 +94,11 @@
     #output {
 	width: 100%;
     }
+    #error {
+	font-family: monospace;
+	color: red;
+	white-space: pre-wrap;
+    }
   </style>
 </head>
 
@@ -123,8 +128,10 @@
 	<textarea id="code" rows="15" width="100%"></textarea>
 	<button type="submit">Run code</button>
       </form>
+      <div id="error">
+      </div>
       <img id="output"></img>
-    </div>
+   </div>
 
     <button id="jumpstart">
       Jumpstart Magic School Bus
@@ -147,6 +154,7 @@
     const welcome_message = document.getElementById("welcome-message");
     const jumpstart = document.getElementById("jumpstart");
     const output = document.getElementById("output");
+    const error = document.getElementById("error");
 
     function fade_element(elt) {
 	elt.style.opacity = "100%";
@@ -192,6 +200,10 @@
 	}
     });
 
+    socket.on('error', (error_message) => {
+	error.textContent = error_message;
+    });
+
     socket.on('state', (state) => {
 	if (state === "program") {
 	    welcome.style.visibility = "hidden";
@@ -208,6 +220,7 @@
     });
 
     socket.on('output', (filename) => {
+	error.textContent = "";
 	output.src = filename;
     });
 
diff --git a/index.js b/index.js
index 2f99074..bfa6d8a 100644
--- a/index.js
+++ b/index.js
@@ -300,7 +300,8 @@ io_bus.on("connection", (socket) => {
 	    // Give all clients the new image
 	    io_bus.emit('output', filename);
 	} catch (e) {
-	    console.log("Error executing turtle script: " + e);
+	    // Send any error out to the users
+	    io_bus.emit('error', e.toString())
 	}
     });
 
-- 
2.43.0