FF-1718: new flow element variable exists

BasicNodes/File/FileExists.cs

@@ -15,7 +15,7 @@ public class FileExists: Node
     /// <inheritdoc />
     public override FlowElementType Type => FlowElementType.Logic;
     /// <inheritdoc />
-    public override string Icon => "fas fa-question-circle";
+    public override string Icon => "fas fa-question";
     /// <inheritdoc />
     public override string HelpUrl => "https://fileflows.com/docs/plugins/basic-nodes/file-exists";
     /// <inheritdoc />

BasicNodes/File/VariableExists.cs

@@ -0,0 +1,56 @@
+using FileFlows.Plugin;
+using FileFlows.Plugin.Attributes;
+
+namespace FileFlows.BasicNodes.File;
+
+/// <summary>
+/// Checks if a file exists
+/// </summary>
+public class VariableExists: Node
+{
+    /// <inheritdoc />
+    public override int Inputs => 1;
+    /// <inheritdoc />
+    public override int Outputs => 2;
+    /// <inheritdoc />
+    public override FlowElementType Type => FlowElementType.Logic;
+    /// <inheritdoc />
+    public override string Icon => "fas fa-question";
+    /// <inheritdoc />
+    public override string HelpUrl => "https://fileflows.com/docs/plugins/basic-nodes/variable-exists";
+    /// <inheritdoc />
+    public override bool NoEditorOnAdd => true;
+
+
+    /// <summary>
+    /// Gets or sets the name of the variable to check
+    /// </summary>
+    [Text(1)]
+    public string Variable { get; set; }
+
+    /// <inheritdoc />
+    public override int Execute(NodeParameters args)
+    {
+        string variable = Variable;
+        if(string.IsNullOrWhiteSpace(variable))
+        {
+            args.FailureReason = "Variable not set";
+            args.Logger?.ELog(args.FailureReason);
+            return -1;
+        }
+
+        if (args.Variables.TryGetValue(variable, out var value) == false)
+        {
+            args.Logger?.ILog("Variable does not exist");
+            return 2;
+        }
+        if (value == null)
+        {
+            args.Logger?.ILog("Variable exists but is null");
+            return 2;
+        }
+        
+        args.Logger?.ILog("Variable exists and is not null");
+        return 1;
+    }
+}