From 64cf14ed92db8bb75b0b029fb28828bb23774af7 Mon Sep 17 00:00:00 2001
From: Anand Chitipothu <anandology@gmail.com>
Date: Fri, 7 May 2021 18:29:50 +0530
Subject: [PATCH] fix: fail gracefully when livecode_to_svg crashes

That seems to be happening in some cases and couldn't really figure out
the reason. Handling the error to gracefully to show an empty image in
those cases.
---
 community/lms/doctype/lms_sketch/livecode.py  | 40 ++++++++++---------
 .../lms/doctype/lms_sketch/lms_sketch.py      | 10 ++++-
 2 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/community/lms/doctype/lms_sketch/livecode.py b/community/lms/doctype/lms_sketch/livecode.py
index e0cf2312..8ea05ddd 100644
--- a/community/lms/doctype/lms_sketch/livecode.py
+++ b/community/lms/doctype/lms_sketch/livecode.py
@@ -3,6 +3,7 @@
 import websocket
 import json
 from .svg import SVG
+import frappe
 
 # Files to pass to livecode server
 # The same code is part of livecode-canvas.js
@@ -62,26 +63,29 @@ clear()
 def livecode_to_svg(livecode_ws_url, code, *, timeout=3):
     """Renders the code as svg.
     """
-    ws = websocket.WebSocket()
-    ws.settimeout(timeout)
-    ws.connect(livecode_ws_url)
+    try:
+        ws = websocket.WebSocket()
+        ws.settimeout(timeout)
+        ws.connect(livecode_ws_url)
 
-    msg = {
-        "msgtype": "exec",
-        "runtime": "python",
-        "code": code,
-        "files": [
-            {"filename": "start.py", "contents": START},
-            {"filename": "sketch.py", "contents": SKETCH},
-        ],
-        "command": ["python", "start.py"]
-    }
-    ws.send(json.dumps(msg))
+        msg = {
+            "msgtype": "exec",
+            "runtime": "python",
+            "code": code,
+            "files": [
+                {"filename": "start.py", "contents": START},
+                {"filename": "sketch.py", "contents": SKETCH},
+            ],
+            "command": ["python", "start.py"]
+        }
+        ws.send(json.dumps(msg))
 
-    messages = _read_messages(ws)
-    commands = [m for m in messages if m['msgtype'] == 'draw']
-    img = draw_image(commands)
-    return img.tostring()
+        messages = _read_messages(ws)
+        commands = [m for m in messages if m['msgtype'] == 'draw']
+        img = draw_image(commands)
+        return img.tostring()
+    except websocket.WebSocketException as e:
+        frappe.log_error(frappe.get_traceback(), 'livecode_to_svg failed')
 
 def _read_messages(ws):
     messages = []
diff --git a/community/lms/doctype/lms_sketch/lms_sketch.py b/community/lms/doctype/lms_sketch/lms_sketch.py
index 474ccf5d..008bc024 100644
--- a/community/lms/doctype/lms_sketch/lms_sketch.py
+++ b/community/lms/doctype/lms_sketch/lms_sketch.py
@@ -9,6 +9,11 @@ import frappe
 from frappe.model.document import Document
 from . import livecode
 
+DEFAULT_IMAGE = """
+<svg viewBox="0 0 300 300" width="300" xmlns="http://www.w3.org/2000/svg">
+</svg>
+"""
+
 class LMSSketch(Document):
     @property
     def sketch_id(self):
@@ -48,8 +53,9 @@ class LMSSketch(Document):
         else:
             ws_url = self.get_livecode_ws_url()
             value = livecode.livecode_to_svg(ws_url, self.code)
-            cache.set(key, value)
-        return value
+            if value:
+                cache.set(key, value)
+        return value or DEFAULT_IMAGE
 
     @staticmethod
     def get_recent_sketches(limit=100, owner=None):