Stops OE from breaking when paused DBs are expanded (#2083)

* Send session failed notification for paused DBs

* Creates error node when connections fail

* Revert "Send session failed notification for paused DBs"

This reverts commit 1f09d8adf9aadb61a7644f84f40558710b0ba5f2.

* Adjusts error node label

* Code clean up

* Update src/Microsoft.SqlTools.ServiceLayer/ObjectExplorer/ObjectExplorerService.cs

Co-authored-by: Charles Gagnon <chgagnon@microsoft.com>

* Cleans up error node info creation

* Rename create error node method

---------

Co-authored-by: Charles Gagnon <chgagnon@microsoft.com>

src/Microsoft.SqlTools.ServiceLayer/ObjectExplorer/Contracts/NodeInfo.cs

@@ -78,6 +78,31 @@ namespace Microsoft.SqlTools.ServiceLayer.ObjectExplorer.Contracts
         public NodeFilterProperty[] FilterableProperties { get; set; }
     }
 
+    /// <summary>
+    /// Creates a NodeInfo and configures it for error situations
+    /// </summary>
+    public static class ErrorNodeInfo
+    {
+        /// <summary>
+        /// Helper function to create an error node.
+        /// </summary>
+        /// <param name="parentNodePath">The parent node the error node will appear under</param>
+        /// <param name="errorMessage">The error message to display in the error node</param>
+        /// <returns>NodeInfo instance with the specified parent path and error message</returns>
+        public static NodeInfo Create(string parentNodePath, string errorMessage)
+        {
+            return new NodeInfo()
+            {
+                ParentNodePath = parentNodePath,
+                ErrorMessage = errorMessage,
+                Label = errorMessage,
+                ObjectType = "error",
+                NodeType = "error",
+                IsLeaf = true
+            };
+        }
+    }
+
     /// <summary>
     /// The filterable properties that a node supports
     /// </summary>

src/Microsoft.SqlTools.ServiceLayer/ObjectExplorer/ObjectExplorerService.cs

@@ -1,4 +1,4 @@
-//
+//
 // Copyright (c) Microsoft. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 //
@@ -453,7 +453,18 @@ namespace Microsoft.SqlTools.ServiceLayer.ObjectExplorer
                                else
                                {
                                    Logger.Verbose($"Expanding {nodePath}");
-                                   nodes = node.Expand(cancelToken, securityToken?.Token, filters).Select(x => x.ToNodeInfo()).ToArray();
+                                   try
+                                   {
+                                       nodes = node.Expand(cancelToken, securityToken?.Token, filters).Select(x => x.ToNodeInfo()).ToArray();
+                                   }
+                                   catch (ConnectionFailureException ex)
+                                   {
+                                       var errorMessage = ex.InnerException?.Message ?? ex.Message;
+
+                                       Logger.Error($"Failed to expand node: {errorMessage}");
+                                       var errorNode = ErrorNodeInfo.Create(parentNodePath: nodePath, errorMessage: errorMessage);
+                                       nodes = new NodeInfo[] { errorNode };
+                                   }
                                }
                                response.Nodes = nodes;
                                response.ErrorMessage = node.ErrorMessage;