service/dynamodb/expression: Add IsSet helper for ConditionBuilder and KeyConditionBuilder

CHANGELOG_PENDING.md

@@ -9,6 +9,9 @@ SDK Features
 
 SDK Enhancements
 ---
+* `service/dynamodb/expression`: Add IsSet helper for ConditionBuilder and KeyConditionBuilder ([#494](https://github.com/aws/aws-sdk-go-v2/pull/494))
+  * Adds a IsSet helper for ConditionBuilder and KeyConditionBuilder to make it easier to determine if the condition builders have any conditions added to them.
+  * Implements [#493](https://github.com/aws/aws-sdk-go-v2/issues/493).
 
 SDK Bugs
 ---

service/dynamodb/expression/condition.go

@@ -88,6 +88,22 @@ type ConditionBuilder struct {
 	mode          conditionMode
 }
 
+// IsSet returns true if the provided ConditionBuilder is set and returns false
+// otherwise. A zero value of a ConditionBuilder returns false.
+//
+// Example:
+//
+//     var condition expression.ConditionBuilder
+//     expression.IsSet(condition) // returns false
+//
+//     expression.IsSet(expression.ConditionBuilder{}) // returns false
+//
+//     condition := expression.Equal(expression.Name("foo"), expression.Value(5))
+//     expressions.IsSet(condition) // returns true
+func IsSet(builder ConditionBuilder) bool {
+	return builder.mode != unsetCond
+}
+
 // Equal returns a ConditionBuilder representing the equality clause of the two
 // argument OperandBuilders. The resulting ConditionBuilder can be used as a
 // part of other Condition Expressions or as an argument to the WithCondition()

service/dynamodb/expression/condition_test.go

@@ -24,6 +24,32 @@ const (
 	invalidConditionOperand = "BuildOperand error"
 )
 
+func TestIsSet(t *testing.T) {
+	cases := []struct {
+		name     string
+		input    ConditionBuilder
+		expected bool
+	}{
+		{
+			name:     "set",
+			input:    Equal(Name("foo"), Value("bar")),
+			expected: true,
+		},
+		{
+			name:     "unset",
+			input:    ConditionBuilder{},
+			expected: false,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if actual := IsSet(c.input); actual != c.expected {
+				t.Errorf("expected %t, got %t", c.expected, actual)
+			}
+		})
+	}
+}
+
 //Compare
 func TestCompare(t *testing.T) {
 	cases := []struct {

service/dynamodb/expression/key_condition.go

@@ -40,6 +40,22 @@ type KeyConditionBuilder struct {
 	mode             keyConditionMode
 }
 
+// IsKeySet returns true if the provided KeyConditionBuilder is set and returns
+// false otherwise. A zero value of a KeyConditionBuilder returns false.
+//
+// Example:
+//
+//     var keyCondition expression.KeyConditionBuilder
+//     expression.IsKeySet(keyCondition) // returns false
+//
+//     expression.IsKeySet(expression.KeyConditionBuilder{}) // returns false
+//
+//     keyCondition := expression.KeyEqual(expression.Key("foo"), expression.Value(5))
+//     expressions.IsKeySet(keyCondition) // returns true
+func IsKeySet(builder KeyConditionBuilder) bool {
+	return builder.mode != unsetKeyCond
+}
+
 // KeyEqual returns a KeyConditionBuilder representing the equality clause
 // of the two argument OperandBuilders. The resulting KeyConditionBuilder can be
 // used as a part of other Key Condition Expressions or as an argument to the

service/dynamodb/expression/key_condition_test.go

@@ -27,6 +27,32 @@ const (
 	invalidKeyConditionFormat = "buildKeyCondition error: invalid key condition constructed"
 )
 
+func TestIsKeySet(t *testing.T) {
+	cases := []struct {
+		name     string
+		input    KeyConditionBuilder
+		expected bool
+	}{
+		{
+			name:     "set",
+			input:    KeyEqual(Key("foo"), Value("bar")),
+			expected: true,
+		},
+		{
+			name:     "unset",
+			input:    KeyConditionBuilder{},
+			expected: false,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if actual := IsKeySet(c.input); actual != c.expected {
+				t.Errorf("expected %t, got %t", c.expected, actual)
+			}
+		})
+	}
+}
+
 func TestKeyCompare(t *testing.T) {
 	cases := []struct {
 		name         string