Fixed Exp not returning the correct error value. (#2231)

Author: AdrianEPPlus

src/EPPlus/FormulaParsing/Excel/Operators/Operator.cs

@@ -10,14 +10,12 @@ Date               Author                       Change
  *************************************************************************************************
   01/27/2020         EPPlus Software AB       Initial release EPPlus 5
  *************************************************************************************************/
-using System;
 using OfficeOpenXml.FormulaParsing.FormulaExpressions;
-using OfficeOpenXml.FormulaParsing.Exceptions;
 using OfficeOpenXml.FormulaParsing.LexicalAnalysis;
-using System.Diagnostics;
 using OfficeOpenXml.FormulaParsing.Ranges;
-using OfficeOpenXml.FormulaParsing.Excel.Functions.MathFunctions;
 using OfficeOpenXml.Utils.TypeConversion;
+using System;
+using System.Diagnostics;
 
 namespace OfficeOpenXml.FormulaParsing.Excel.Operators
 {
@@ -288,6 +286,18 @@ public static IOperator Exp
                             var res = Math.Pow(l.ResultNumeric, r.ResultNumeric);
                             return CreateCompileResult(l.ResultType, r.ResultType, res, DataType.Decimal);
                         }
+                        if (l.DataType == DataType.String || r.DataType == DataType.String)
+                        {
+                            return CompileResult.GetErrorResult(eErrorType.Value);
+                        }
+                        if (l.Result is ExcelErrorValue)
+                        {
+                            return new CompileResult(l.Result, DataType.ExcelError);
+                        }
+                        else if (r.Result is ExcelErrorValue)
+                        {
+                            return new CompileResult(r.Result, DataType.ExcelError);
+                        }
                         return CompileResult.ZeroDecimal;
                     });
             }

src/EPPlusTest/Issues/LegacyTests/Issues.cs

@@ -6315,5 +6315,22 @@ public void ReadCustomXml2()
             Assert.AreEqual(12, p.Workbook.CustomXmlDocuments[2].SchemasReferences.Count);
             SaveAndCleanup(p);
         }
+        [TestMethod]
+        public void s985()
+        {
+            using var pkg = new ExcelPackage();
+            var ws = pkg.Workbook.Worksheets.Add("Pow");
+            ws.Cells["A1"].Value = "x";
+            ws.Cells["B1"].Formula = "A1^2";
+            ws.Cells["C1"].Formula = "2^A1";
+            ws.Cells["D1"].Formula = "x^2";
+            ws.Cells["E1"].Formula = "2^x";
+            ws.Calculate();
+            Assert.AreEqual(ExcelErrorValue.Create(eErrorType.Value), ws.Cells["B1"].Value);
+            Assert.AreEqual(ExcelErrorValue.Create(eErrorType.Value), ws.Cells["C1"].Value);
+            Assert.AreEqual(ExcelErrorValue.Create(eErrorType.Name), ws.Cells["D1"].Value);
+            Assert.AreEqual(ExcelErrorValue.Create(eErrorType.Name), ws.Cells["E1"].Value);
+        }
     }
 }
+