fix ddb crash if condition produces empty value

fogfish · Oct 31, 2020 · ac085dd · ac085dd
1 parent a8f61c2
commit ac085dd
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Showing 2 changed files with 11 additions and 5 deletions.
diff --git a/constrain.go b/constrain.go
@@ -195,7 +195,7 @@ func (e ElemIs) Exists() Config {
 /*
 
 NotExists attribute constrain
-	name.Exists(x) ⟼ attribute_not_exists(name)
+	name.NotExists(x) ⟼ attribute_not_exists(name)
 */
 func (e ElemIs) NotExists() Config {
 	return e.constrain("attribute_not_exists")

diff --git a/ddb.go b/ddb.go
@@ -87,8 +87,11 @@ func (dynamo DB) Put(entity curie.Thing, config ...Config) (err error) {
 		TableName: dynamo.table,
 	}
 	if len(config) > 0 {
-		req.ExpressionAttributeValues = map[string]*dynamodb.AttributeValue{}
-		config[0](&req.ConditionExpression, req.ExpressionAttributeValues)
+		values := map[string]*dynamodb.AttributeValue{}
+		config[0](&req.ConditionExpression, values)
+		if len(values) > 0 {
+			req.ExpressionAttributeValues = values
+		}
 	}
 	_, err = dynamo.db.PutItem(req)
 	if err != nil {
@@ -119,8 +122,11 @@ func (dynamo DB) Remove(entity curie.Thing, config ...Config) (err error) {
 		TableName: dynamo.table,
 	}
 	if len(config) > 0 {
-		req.ExpressionAttributeValues = map[string]*dynamodb.AttributeValue{}
-		config[0](&req.ConditionExpression, req.ExpressionAttributeValues)
+		values := map[string]*dynamodb.AttributeValue{}
+		config[0](&req.ConditionExpression, values)
+		if len(values) > 0 {
+			req.ExpressionAttributeValues = values
+		}
 	}
 
 	_, err = dynamo.db.DeleteItem(req)