fix: Update DocumentModel to handle expressions without variables

Author: dscpinheiro

generator/.DevConfigs/6d15fac7-b782-42ab-a6b8-e2ff4c240df3.json

@@ -0,0 +1,11 @@
+{
+    "services": [
+        {
+            "serviceName": "DynamoDBv2",
+            "type": "patch",
+            "changeLogMessages": [
+                "Fix regression where an `Expression` could not be used without `ExpressionAttributeValues` (https://github.com/aws/aws-sdk-net/issues/3802)"
+            ]
+        }
+    ]
+}

sdk/src/Services/DynamoDBv2/Custom/DocumentModel/Expression.cs

@@ -218,27 +218,29 @@ internal static void ApplyExpression(QueryRequest request, Table table,
         internal static Dictionary<string, AttributeValue> ConvertToAttributeValues(
             Dictionary<string, DynamoDBEntry> valueMap, Table table)
         {
+            if (valueMap == null || valueMap.Count == 0)
+            {
+                return null;
+            }
+
             var convertedValues = new Dictionary<string, AttributeValue>();
-            if (valueMap != null)
+            foreach (var kvp in valueMap)
             {
-                foreach (var kvp in valueMap)
+                var attributeName = kvp.Key;
+                var entry = kvp.Value;
+
+                if (entry == null)
+                    convertedValues[attributeName] = new AttributeValue { NULL = true };
+                else
                 {
-                    var attributeName = kvp.Key;
-                    var entry = kvp.Value;
-
-                    if (entry == null)
-                        convertedValues[attributeName] = new AttributeValue { NULL = true };
-                    else
-                    {
-                        if (table.StoreAsEpoch.Contains(attributeName))
-                            entry = Document.DateTimeToEpochSeconds(entry, attributeName);
-
-                        if (table.StoreAsEpochLong.Contains(attributeName))
-                            entry = Document.DateTimeToEpochSecondsLong(entry, attributeName);
-
-                        var attributeConversionConfig = new DynamoDBEntry.AttributeConversionConfig(table.Conversion, table.IsEmptyStringValueEnabled);
-                        convertedValues[attributeName] = entry.ConvertToAttributeValue(attributeConversionConfig);
-                    }
+                    if (table.StoreAsEpoch.Contains(attributeName))
+                        entry = Document.DateTimeToEpochSeconds(entry, attributeName);
+
+                    if (table.StoreAsEpochLong.Contains(attributeName))
+                        entry = Document.DateTimeToEpochSecondsLong(entry, attributeName);
+
+                    var attributeConversionConfig = new DynamoDBEntry.AttributeConversionConfig(table.Conversion, table.IsEmptyStringValueEnabled);
+                    convertedValues[attributeName] = entry.ConvertToAttributeValue(attributeConversionConfig);
                 }
             }
 

sdk/test/Services/DynamoDBv2/IntegrationTests/DocumentTests.cs

@@ -58,6 +58,7 @@ public void TestTableOperations()
 
                 // Test expressions for put
                 TestExpressionPut(hashTable);
+                TestExpressionPutWithoutValues(hashTable);
 
                 // Test expressions for delete
                 TestExpressionsOnDelete(hashTable);
@@ -137,6 +138,7 @@ public void TestTableOperationsViaBuilder()
 
                 // Test expressions for put
                 TestExpressionPut(hashTable);
+                TestExpressionPutWithoutValues(hashTable);
 
                 // Test expressions for delete
                 TestExpressionsOnDelete(hashTable);
@@ -1755,6 +1757,27 @@ private void TestExpressionPut(ITable hashTable)
             hashTable.DeleteItem(doc);
         }
 
+        private void TestExpressionPutWithoutValues(ITable hashTable)
+        {
+            var doc = new Document
+            {
+                ["Id"] = DateTime.UtcNow.Ticks
+            };
+
+            var expression = new Expression
+            {
+                ExpressionStatement = "attribute_not_exists(Id)"
+            };
+
+            var config = new PutItemOperationConfig
+            {
+                ConditionalExpression = expression
+            };
+
+            Assert.IsTrue(hashTable.TryPutItem(doc, config));
+            hashTable.DeleteItem(doc);
+        }
+
         private void TestExpressionUpdate(ITable hashTable)
         {
             Document doc = new Document();