From ccd7c7063bef6c486951479591895bbf34f22ce9 Mon Sep 17 00:00:00 2001
From: Kasdejong <k.j2.de.jong@student.vu.nl>
Date: Wed, 28 Aug 2024 11:50:04 +0200
Subject: [PATCH] It really was this easy?

---
 .../FhirPath/Expressions/SymbolTableInit.cs     | 14 ++++++--------
 .../PocoTests/FhirPathEvaluatorTest.cs          | 17 ++++++-----------
 2 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/src/Hl7.Fhir.Base/FhirPath/Expressions/SymbolTableInit.cs b/src/Hl7.Fhir.Base/FhirPath/Expressions/SymbolTableInit.cs
index 48df4ef9d..e7544ce47 100644
--- a/src/Hl7.Fhir.Base/FhirPath/Expressions/SymbolTableInit.cs
+++ b/src/Hl7.Fhir.Base/FhirPath/Expressions/SymbolTableInit.cs
@@ -328,14 +328,12 @@ private static IEnumerable<ITypedElement> runIif(Closure ctx, IEnumerable<Invoke
         {
             // iif(criterion: expression, true-result: collection [, otherwise-result: collection]) : collection
             // note: short-circuit behavior is expected in this function
-            
             var focus = arguments.First()(ctx, InvokeeFactory.EmptyArgs);
-            if (focus.Count() > 1)
-            {
-                return runSelect(ctx, [arguments.First(), (closure, _) => runIif(closure, new List<Invokee>{(_, _) => closure.GetThis(), arguments.Skip(1).First(), arguments.Skip(2).First(), arguments.Skip(3).FirstOrDefault()})]);
-            }
 
-            var expression = arguments.Skip(1).First()(ctx, InvokeeFactory.EmptyArgs);
+            var newContext = ctx.Nest(focus);
+            newContext.SetThis(focus);
+            
+            var expression = arguments.Skip(1).First()(newContext, InvokeeFactory.EmptyArgs);
             var trueResult = arguments.Skip(2).First();
             var otherResult = arguments.Skip(3).FirstOrDefault();
 
@@ -343,8 +341,8 @@ private static IEnumerable<ITypedElement> runIif(Closure ctx, IEnumerable<Invoke
                 throw Error.InvalidOperation($"Result of {nameof(expression)} is not of type boolean");
 
             return (expression.BooleanEval() ?? false)
-                ? trueResult(ctx, InvokeeFactory.EmptyArgs)
-                : otherResult == null ? ElementNode.EmptyList : otherResult(ctx, InvokeeFactory.EmptyArgs);
+                ? trueResult(newContext, InvokeeFactory.EmptyArgs) // share focus with this function
+                : otherResult == null ? ElementNode.EmptyList : otherResult(newContext, InvokeeFactory.EmptyArgs);
         }
 
         private static IEnumerable<ITypedElement> runWhere(Closure ctx, IEnumerable<Invokee> arguments)
diff --git a/src/Hl7.FhirPath.R4.Tests/PocoTests/FhirPathEvaluatorTest.cs b/src/Hl7.FhirPath.R4.Tests/PocoTests/FhirPathEvaluatorTest.cs
index a3363485c..b2b1eff45 100644
--- a/src/Hl7.FhirPath.R4.Tests/PocoTests/FhirPathEvaluatorTest.cs
+++ b/src/Hl7.FhirPath.R4.Tests/PocoTests/FhirPathEvaluatorTest.cs
@@ -22,6 +22,7 @@
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Reflection.Metadata.Ecma335;
 using System.Xml.Linq;
 
 namespace Hl7.FhirPath.R4.Tests
@@ -164,18 +165,12 @@ public void TestSubsetting()
 
 
         [TestMethod]
-        public void TestIIf()
+        public void TestIIfContext()
         {
-            fixture.IsTrue(@"Patient.contained[0].name.iif(exists(), 'named', 'unnamed').join(', ') = 'named, named'");
-            fixture.IsTrue(@"Patient.contained[0].name.iif(empty(), 'unnamed', 'named').join(', ') = 'named, named'");
-            fixture.IsTrue(@"Patient.name.iif({}, 'named', 'unnamed').join(', ') = 'unnamed'");
-            
-            var resultWithSelect = fixture.PatientExample.Select("Patient.name.select(iif(use = 'official', given, 'not official')).join(', ')");
-            var resultWithoutSelect = fixture.PatientExample.Select("Patient.name.iif(use = 'official', given, 'not official').join(', ')");
-            resultWithSelect.Should().BeEquivalentTo(resultWithoutSelect);
-            resultWithSelect.Should().ContainSingle().Subject.Should().BeEquivalentTo(new FhirString("Peter, James, not official"));
-            
-            //   fixture.IsTrue(@"Patient.name[0].family.iif(length()-8 != 0, 5/(length()-8), 'no result') = 'no result'");
+            var res = fixture.TestInput.Scalar("Patient.contained[0].name[0].given[0].iif(true, single())");
+            res.Should().BeOfType<string>().Subject.Should().Be("Eve");
+            res = fixture.TestInput.Scalar("Patient.contained[0].name.iif(use = 'official', 'given', given.join(''))"); // comparison between collection and string
+            res.Should().BeOfType<string>().Subject.Should().Be("EveEveline");
         }
 
         [TestMethod]