Attempt at fixing plotting errors on deployed app

src/App.jsx

@@ -1,5 +1,5 @@
 // * Imports *
 import { useState, useCallback, useEffect, useRef, version } from 'react';
 import {
   ReactFlowProvider,
   useReactFlow,
@@ -90,7 +90,7 @@
   }, []);
 
   const onDragStart = (event, nodeType) => {
     setType(nodeType);
     event.dataTransfer.setData('text/plain', nodeType);
     event.dataTransfer.effectAllowed = 'move';
   };
@@ -107,7 +107,7 @@
   const [pythonCode, setPythonCode] = useState("# Define your Python variables and functions here\n# Example:\n# my_variable = 42\n# def my_function(x):\n#     return x * 2\n");
 
   // State for URL sharing feedback
   const [shareUrlFeedback, setShareUrlFeedback] = useState('');
   const [showShareModal, setShowShareModal] = useState(false);
   const [shareableURL, setShareableURL] = useState('');
   const [urlMetadata, setUrlMetadata] = useState(null);
@@ -161,7 +161,7 @@
     };
 
     loadGraphFromURL();
   }, []); // Empty dependency array means this runs once on mount
 
   const [defaultValues, setDefaultValues] = useState({});
   const [isEditingLabel, setIsEditingLabel] = useState(false);
@@ -366,7 +366,7 @@
       setNodes((nds) => [...nds, newNode]);
       setNodeCounter((count) => count + 1);
     },
     [screenToFlowPosition, type, nodeCounter, fetchDefaultValues, setDefaultValues, setNodes, setNodeCounter],
   );
 
   // Function to save a graph to computer with "Save As" dialog
@@ -791,7 +791,25 @@
         body: JSON.stringify({ graph: graphData }),
       });
 
-      const result = await response.json();
+      // Check if response is ok first
+      if (!response.ok) {
+        throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+      }
+
+      // Check if response has content
+      const responseText = await response.text();
+      if (!responseText.trim()) {
+        throw new Error('Server returned empty response');
+      }
+
+      // Try to parse JSON
+      let result;
+      try {
+        result = JSON.parse(responseText);
+      } catch (jsonError) {
+        console.error('Failed to parse JSON response:', responseText);
+        throw new Error(`Invalid JSON response: ${jsonError.message}`);
+      }
 
       if (sseRef.current) { sseRef.current.close(); sseRef.current = null; }
 
@@ -805,8 +823,29 @@
         alert(`Error running Pathsim simulation: ${result.error}`);
       }
     } catch (error) {
-      console.error('Error:', error);
-      alert(`Failed to run Pathsim simulation. Make sure the backend is running. : ${error.message}`);
+      console.error('Error details:', {
+        message: error.message,
+        stack: error.stack,
+        response: error.response || 'No response object'
+      });
+
+      if (sseRef.current) {
+        sseRef.current.close();
+        sseRef.current = null;
+      }
+
+      // Provide more specific error messages
+      let errorMessage = 'Failed to run Pathsim simulation. Make sure the backend is running.';
+
+      if (error.message.includes('JSON')) {
+        errorMessage = 'Server response was not valid JSON. This might be due to a server error or network issue.';
+      } else if (error.message.includes('HTTP')) {
+        errorMessage = `Server error: ${error.message}`;
+      } else if (error.message.includes('empty response')) {
+        errorMessage = 'Server returned empty response. The simulation might have failed silently.';
+      }
+
+      alert(`${errorMessage} : ${error.message}`);
     }
   };
 
@@ -1052,7 +1091,7 @@
     return () => {
       document.removeEventListener('keydown', handleKeyDown);
     };
   }, [selectedEdge, selectedNode, copiedNode, duplicateNode, setCopyFeedback]);
 
   return (
     <div style={{ width: '100vw', height: '100vh', display: 'flex', flexDirection: 'column' }}>

src/backend.py

@@ -20,7 +20,6 @@
 
 # imports for logging progress
 from flask import Response, stream_with_context
-import time
 import logging
 from queue import Queue, Empty
 
@@ -94,9 +93,18 @@ def logs_stream():
     def gen():
         yield "retry: 500\n\n"
         while True:
-            line = log_queue.get()
-            for chunk in line.replace("\r", "\n").splitlines():
-                yield f"data: {chunk}\n\n"
+            try:
+                # Use a timeout to prevent indefinite blocking
+                line = log_queue.get(timeout=30)
+                for chunk in line.replace("\r", "\n").splitlines():
+                    yield f"data: {chunk}\n\n"
+            except Empty:
+                # Send a heartbeat to keep connection alive
+                yield "data: \n\n"
+            except Exception as e:
+                # Log the error and break the loop to close the connection
+                yield f"data: Error in log stream: {str(e)}\n\n"
+                break
 
     return Response(gen(), mimetype="text/event-stream")
 
@@ -358,6 +366,19 @@ def run_pathsim():
         # Share x only if there are only scopes or only spectra
         shared_x = len(scopes) * len(spectra) == 0
         n_rows = len(scopes) + len(spectra)
+
+        if n_rows == 0:
+            # No scopes or spectra to plot
+            return jsonify(
+                {
+                    "success": True,
+                    "plot": "{}",
+                    "html": "<p>No scopes or spectra to display</p>",
+                    "csv_data": csv_payload,
+                    "message": "Pathsim simulation completed successfully",
+                }
+            )
+
         absolute_vertical_spacing = 0.05
         relative_vertical_spacing = absolute_vertical_spacing / n_rows
         fig = make_subplots(
@@ -371,27 +392,27 @@ def run_pathsim():
 
         # make scope plots
         for i, scope in enumerate(scopes):
-            time, data = scope.read()
+            sim_time, data = scope.read()
 
             for p, d in enumerate(data):
                 lb = scope.labels[p] if p < len(scope.labels) else f"port {p}"
                 if isinstance(scope, Spectrum):
                     d = abs(d)
                 fig.add_trace(
-                    go.Scatter(x=time, y=d, mode="lines", name=lb), row=i + 1, col=1
+                    go.Scatter(x=sim_time, y=d, mode="lines", name=lb), row=i + 1, col=1
                 )
 
             fig.update_xaxes(title_text="Time", row=len(scopes), col=1)
 
         # make spectrum plots
         for i, spec in enumerate(spectra):
-            time, data = spec.read()
+            freq, data = spec.read()
 
             for p, d in enumerate(data):
                 lb = spec.labels[p] if p < len(spec.labels) else f"port {p}"
                 d = abs(d)
                 fig.add_trace(
-                    go.Scatter(x=time, y=d, mode="lines", name=lb),
+                    go.Scatter(x=freq, y=d, mode="lines", name=lb),
                     row=len(scopes) + i + 1,
                     col=1,
                 )
@@ -402,8 +423,13 @@ def run_pathsim():
         )
 
         # Convert plot to JSON
-        plot_data = plotly_json.dumps(fig, cls=plotly.utils.PlotlyJSONEncoder)
-        plot_html = fig.to_html()
+        try:
+            plot_data = plotly_json.dumps(fig, cls=plotly.utils.PlotlyJSONEncoder)
+            plot_html = fig.to_html()
+        except Exception as plot_error:
+            return jsonify(
+                {"success": False, "error": f"Plot generation error: {str(plot_error)}"}
+            ), 500
 
         return jsonify(
             {
@@ -416,6 +442,11 @@ def run_pathsim():
         )
 
     except Exception as e:
+        # Log the full error for debugging
+        import traceback
+
+        error_details = traceback.format_exc()
+        print(f"Error in run_pathsim: {error_details}")
         return jsonify({"success": False, "error": f"Server error: {str(e)}"}), 500
 
 
@@ -503,6 +534,25 @@ def catch_all(path):
         return jsonify({"error": "Route not found"}), 404
 
 
+# Global error handler to ensure all errors return JSON
+@app.errorhandler(Exception)
+def handle_exception(e):
+    """Global exception handler to ensure JSON responses."""
+    import traceback
+
+    error_details = traceback.format_exc()
+    print(f"Unhandled exception: {error_details}")
+
+    # For HTTP exceptions, return the original response
+    if hasattr(e, "code"):
+        return jsonify(
+            {"success": False, "error": f"HTTP {e.code}: {str(e)}"}
+        ), getattr(e, "code", 500)
+
+    # For all other exceptions, return a generic JSON error
+    return jsonify({"success": False, "error": f"Internal server error: {str(e)}"}), 500
+
+
 if __name__ == "__main__":
     port = int(os.getenv("PORT", 8000))
     app.run(host="0.0.0.0", port=port, debug=os.getenv("FLASK_ENV") != "production")