Implement special IIF method to run only ifTrue|ifFalse according test …

…#1458
mbdavid · Feb 9, 2020 · 0628f8e · 0628f8e
1 parent 35e4935
commit 0628f8e
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Showing 3 changed files with 53 additions and 9 deletions.
diff --git a/LiteDB.Tests/Expressions/Expressions_Tests.cs b/LiteDB.Tests/Expressions/Expressions_Tests.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using FluentAssertions;
+using System.Collections.Generic;
 using Xunit;
 
 namespace LiteDB.Tests.Expressions
@@ -228,7 +229,25 @@ public void Expression_AndAlso_OrElse()
             // KO (expected: false, actual: exception)
             doc1["x"] = "123";
             var r2 = ex1.ExecuteScalar(doc1);
-
+        }
+
+        [Fact]
+        public void Expression_Conditional_IIF()
+        {
+            var ex1 = BsonExpression.Create("IIF(LENGTH($.x) >= 5, SUBSTRING($.x, 0, 5), \"too-short\")");
+            var doc1 = new BsonDocument();
+
+            // OK ("12345")
+            doc1["x"] = "123456789";
+            var r1 = ex1.ExecuteScalar(doc1);
+
+            r1.AsString.Should().Be("12345");
+
+            // KO (expected: "too-short", actual: System.ArgumentOutOfRangeException: Index and length must refer to a location within the string.)
+            doc1["x"] = "123";
+            var r2 = ex1.ExecuteScalar(doc1);
+
+            r2.AsString.Should().Be("too-short");
         }
     }
 }
diff --git a/LiteDB/Document/Expression/Methods/Misc.cs b/LiteDB/Document/Expression/Methods/Misc.cs
@@ -119,14 +119,11 @@ public static BsonValue OID_CREATIONTIME(BsonValue objectId)
         /// <summary>
         /// Conditional IF statment. If condition are true, returns TRUE value, otherwise, FALSE value
         /// </summary>
-        public static BsonValue IIF(BsonValue condition, BsonValue ifTrue, BsonValue ifFalse)
+        public static BsonValue IIF(BsonValue test, BsonValue ifTrue, BsonValue ifFalse)
         {
-            if (condition.IsBoolean)
-            {
-                return condition.AsBoolean ? ifTrue : ifFalse;
-            }
-
-            return BsonValue.Null;
+            // this method are not implemented because will use "Expression.Conditional"
+            // will execute "ifTrue" only if test = true and will execute "ifFalse" if test = false
+            throw new NotImplementedException();
         }
 
         /// <summary>

diff --git a/LiteDB/Document/Expression/Parser/BsonExpressionParser.cs b/LiteDB/Document/Expression/Parser/BsonExpressionParser.cs
@@ -931,6 +931,9 @@ private static BsonExpression TryParseMethodCall(Tokenizer tokenizer, Expression
                 }
             }
 
+            // special IIF case
+            if (method.Name == "IIF" && pars.Count == 3) return CreateConditionalExpression(pars[0], pars[1], pars[2]);
+
             return new BsonExpression
             {
                 Type = BsonExpressionType.Call,
@@ -1433,5 +1436,30 @@ internal static BsonExpression CreateLogicExpression(BsonExpressionType type, Bs
 
             return result;
         }
+
+        /// <summary>
+        /// Create new conditional (IIF) expression. Execute expression only if True or False value
+        /// </summary>
+        internal static BsonExpression CreateConditionalExpression(BsonExpression test, BsonExpression ifTrue, BsonExpression ifFalse)
+        {
+            // convert BsonValue into Boolean
+            var boolTest = Expression.Property(test.Expression, typeof(BsonValue), "AsBoolean");
+
+            var expr = Expression.Condition(boolTest, ifTrue.Expression, ifFalse.Expression);
+
+            // create new binary expression based in 2 other expressions
+            var result = new BsonExpression
+            {
+                Type = BsonExpressionType.Call, // there is not specific Conditional
+                IsImmutable = test.IsImmutable && ifTrue.IsImmutable || ifFalse.IsImmutable,
+                UseSource = test.UseSource || ifTrue.UseSource || ifFalse.UseSource,
+                IsScalar = test.IsScalar && ifTrue.IsScalar && ifFalse.IsScalar,
+                Fields = new HashSet<string>(StringComparer.OrdinalIgnoreCase).AddRange(test.Fields).AddRange(ifTrue.Fields).AddRange(ifFalse.Fields),
+                Expression = expr,
+                Source = "IIF(" + test.Source + "," + ifTrue.Source + "," + ifFalse.Source + ")"
+            };
+
+            return result;
+        }
     }
 }