Fixed null type conversion

Fixes #314
MarkMpn · Jun 28, 2023 · 0c27af7 · 0c27af7
1 parent da6c9f3
commit 0c27af7
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Showing 2 changed files with 26 additions and 5 deletions.
diff --git a/MarkMpn.Sql4Cds.Engine.Tests/AdoProviderTests.cs b/MarkMpn.Sql4Cds.Engine.Tests/AdoProviderTests.cs
@@ -1224,5 +1224,26 @@ SELECT 2 + 2
                 Assert.AreEqual("<row>4</row>", actual);
             }
         }
+
+        [TestMethod]
+        public void UpdateCase()
+        {
+            // https://github.com/MarkMpn/Sql4Cds/issues/314
+            using (var con = new Sql4CdsConnection(_localDataSource))
+            using (var cmd = con.CreateCommand())
+            {
+                cmd.CommandTimeout = 0;
+
+                cmd.CommandText = "INSERT INTO account (employees) VALUES (1)";
+                cmd.ExecuteNonQuery();
+
+                cmd.CommandText = "UPDATE a SET a.employees = (CASE WHEN a.employees IS NULL THEN NULL ELSE a.employees + 1 END) FROM account AS a WHERE a.accountid IS NOT NULL";
+                cmd.ExecuteNonQuery();
+
+                cmd.CommandText = "SELECT employees FROM account";
+                var actual = cmd.ExecuteScalar();
+                Assert.AreEqual(2, actual);
+            }
+        }
     }
 }
diff --git a/MarkMpn.Sql4Cds.Engine/ExecutionPlan/SqlTypeConverter.cs b/MarkMpn.Sql4Cds.Engine/ExecutionPlan/SqlTypeConverter.cs
@@ -194,19 +194,19 @@ private static void AddNullableTypeConversion<TSql, TNet>(Func<DataSource, TNet,
         /// <returns><c>true</c> if the two values can be converted to a consistent type, or <c>false</c> otherwise</returns>
         public static bool CanMakeConsistentTypes(DataTypeReference lhs, DataTypeReference rhs, DataSource primaryDataSource, out DataTypeReference consistent)
         {
-            if (lhs.IsSameAs(rhs))
+            if (lhs == DataTypeHelpers.ImplicitIntForNullLiteral)
             {
-                consistent = lhs;
+                consistent = rhs;
                 return true;
             }
 
-            if (lhs == DataTypeHelpers.ImplicitIntForNullLiteral)
+            if (rhs == DataTypeHelpers.ImplicitIntForNullLiteral)
             {
-                consistent = rhs;
+                consistent = lhs;
                 return true;
             }
 
-            if (rhs == DataTypeHelpers.ImplicitIntForNullLiteral)
+            if (lhs.IsSameAs(rhs))
             {
                 consistent = lhs;
                 return true;