Merge pull request #512 from Altinn/ivarne/linq-to-json-path-improvement

Add a few more cases to the Linq to json path used for CreateValidationIssue

Author: ivarne

src/Altinn.App.Core/Helpers/LinqExpressionHelpers.cs

@@ -92,11 +92,31 @@ private static string GetJsonPath_internal(Expression expression)
             case MemberExpression { Member: FieldInfo fieldInfo, Expression: { } memberExpression }:
                 var evaluatedMember = GetValueFromExpression(memberExpression);
                 return fieldInfo.GetValue(evaluatedMember);
+            // Support for evaluating the member expression on a property (recursively if needed)
+            case MemberExpression { Member: PropertyInfo propertyInfo, Expression: { } memberExpression }:
+                var evaluatedMember2 = GetValueFromExpression(memberExpression);
+                return propertyInfo.GetValue(evaluatedMember2);
+            // Support for evaluating binary expressions in indexers (eg: m=>m.Children[model.Children.Count + 1)
+            case BinaryExpression { Left: { } leftExpr, Right: { } rightExpr } be:
+                var left = GetValueFromExpression(leftExpr) as int? ?? throw new ArgumentException(
+                    $"Missing implementation for {be}.");
+                var right = GetValueFromExpression(rightExpr) as int? ?? throw new ArgumentException(
+                    $"Missing implementation for {be}.");
+                return be.NodeType switch
+                {
+                    ExpressionType.Add => left + right,
+                    ExpressionType.Subtract => left - right,
+                    ExpressionType.Divide => left / right,
+                    ExpressionType.Multiply => left * right,
+                    ExpressionType.Modulo => left % right,
+                    _ => throw new ArgumentException(
+                        $"Missing implementation for {be}.")
+                };
 
             // Currently we just error on unknown expressions
             default:
                 throw new ArgumentException(
-                    $"Invalid indexer expression {expression}. Failed reading {expression}");
+                    $"Missing implementation for {expression.GetType()} {expression}.");
         }
     }
 

test/Altinn.App.Core.Tests/Helpers/LinqExpressionHelpersTests.cs

@@ -76,4 +76,37 @@ public void GetJsonPath_IndexInVariableLoop()
             propertyName.Should().Be($"Children[{index}].age");
         }
     }
+
+    [Fact]
+    public void GetJsonPath_AritmeticExpression()
+    {
+        var list = new List<string>
+        {
+            "one",
+            "two"
+        };
+        var propertyName = LinqExpressionHelpers.GetJsonPath<MyModel, int?>(m => m.Children![list.Count - 1].Age);
+        propertyName.Should().Be("Children[1].age");
+    }
+
+    [Fact]
+    public void GetJsonPath_AritmeticExpressionOnRecursiveModel()
+    {
+        var model = new MyModel
+        {
+            Children = new()
+            {
+                new()
+                {
+                    Age = 3
+                },
+                new()
+                {
+                    Age = 4
+                }
+            }
+        };
+        var propertyName = LinqExpressionHelpers.GetJsonPath<MyModel, int?>(m => m.Children![model.Children.Count + 1].Age);
+        propertyName.Should().Be("Children[3].age");
+    }
 }