Add DoublePointer helper function (#764)

Author: zliang-akamai

pointer_helpers.go

@@ -23,3 +23,29 @@ Example:
 func Pointer[T any](value T) *T {
 	return &value
 }
+
+// DoublePointer creates a double pointer to a value of type T.
+//
+// This is useful for APIs that distinguish between null and omitted fields.
+//
+// Example:
+//
+//	// For a field that should be non-null value in the API payload:
+//	value := linodego.DoublePointer(42) // Returns **int pointing a *int pointer pointing to 42
+//
+//	// For a field that should be null in the API payload, use `DoublePointerNull` function instead:
+//	nullValue := linodego.DoublePointerNull[int]() // Returns **int that is nil
+//
+//	// For a field that should not be included in the API payload, simply not include it in the struct.
+func DoublePointer[T any](value T) **T {
+	valuePtr := &value
+	return &valuePtr
+}
+
+// DoublePointerNull creates a double pointer pointing to a nil pointer of type T,
+// indicating that the field should be null in the API payload.
+//
+// This is useful for APIs that distinguish between null and omitted fields.
+func DoublePointerNull[T any]() **T {
+	return Pointer[*T](nil)
+}

pointer_helpers_test.go

@@ -6,6 +6,12 @@ import (
 
 // TestPointer tests the Pointer helper function with various types
 func TestPointer(t *testing.T) {
+	// Test nil pointer for int (should be nil if explicitly set)
+	nilIntPtr := Pointer[*int](nil)
+	if nilIntPtr == nil || *nilIntPtr != nil {
+		t.Errorf("Expected nil pointer, got %v", nilIntPtr)
+	}
+
 	// Test with an integer
 	intValue := 11
 	intPtr := Pointer(intValue)
@@ -45,3 +51,66 @@ func TestPointer(t *testing.T) {
 		t.Errorf("Expected %+v, got %+v", structValue, *structPtr)
 	}
 }
+
+// TestDoublePointer tests the DoublePointer helper function with various types
+func TestDoublePointer(t *testing.T) {
+	// Test with an integer
+	intValue := 42
+	intDoublePtr := DoublePointer(intValue)
+	if **intDoublePtr != intValue {
+		t.Errorf("Expected %d, got %d", intValue, **intDoublePtr)
+	}
+
+	// Test with a string
+	strValue := "double"
+	strDoublePtr := DoublePointer(strValue)
+	if **strDoublePtr != strValue {
+		t.Errorf("Expected %s, got %s", strValue, **strDoublePtr)
+	}
+
+	// Test with a boolean
+	boolValue := false
+	boolDoublePtr := DoublePointer(boolValue)
+	if **boolDoublePtr != boolValue {
+		t.Errorf("Expected %t, got %t", boolValue, **boolDoublePtr)
+	}
+
+	// Test with a struct
+	type myStruct struct {
+		Field int
+	}
+	structValue := myStruct{Field: 7}
+	structDoublePtr := DoublePointer(structValue)
+	if (**structDoublePtr).Field != structValue.Field {
+		t.Errorf("Expected %+v, got %+v", structValue, **structDoublePtr)
+	}
+}
+
+func TestDoublePointerNull(t *testing.T) {
+	// Test with an integer
+	intDoublePtr := DoublePointerNull[int]()
+	if intDoublePtr == nil || *intDoublePtr != nil {
+		t.Errorf("Expected nil pointer, got %v", intDoublePtr)
+	}
+
+	// Test with a string
+	stringDoublePtr := DoublePointerNull[string]()
+	if stringDoublePtr == nil || *stringDoublePtr != nil {
+		t.Errorf("Expected nil pointer, got %v", stringDoublePtr)
+	}
+
+	// Test with a boolean
+	boolDoublePtr := DoublePointerNull[bool]()
+	if boolDoublePtr == nil || *boolDoublePtr != nil {
+		t.Errorf("Expected nil pointer, got %v", boolDoublePtr)
+	}
+
+	// Test with a struct
+	type myStruct struct {
+		Field int
+	}
+	structDoublePtr := DoublePointerNull[myStruct]()
+	if structDoublePtr == nil || *structDoublePtr != nil {
+		t.Errorf("Expected nil pointer, got %v", structDoublePtr)
+	}
+}

test/integration/mysql_db_config_test.go

@@ -219,7 +219,7 @@ func TestDatabaseMySQL_EngineConfig_Create_Fails_EmptyDoublePointerValue(t *test
 		Engine: "mysql/8",
 		EngineConfig: &linodego.MySQLDatabaseEngineConfig{
 			MySQL: &linodego.MySQLDatabaseEngineConfigMySQL{
-				InnoDBFTServerStopwordTable: DoublePointer(linodego.Pointer("")),
+				InnoDBFTServerStopwordTable: linodego.DoublePointer(""),
 			},
 		},
 	}
@@ -231,10 +231,6 @@ func TestDatabaseMySQL_EngineConfig_Create_Fails_EmptyDoublePointerValue(t *test
 	assert.Contains(t, err.Error(), "Invalid format: must match pattern ^.+/.+$")
 }
 
-func DoublePointer[T any](v *T) **T {
-	return &v
-}
-
 func createMySQLOptionsModifierNullableField() mysqlDatabaseModifier {
 	return func(options *linodego.MySQLCreateOptions) {
 		options.Label = "example-db-created-with-config"
@@ -264,7 +260,7 @@ func createMySQLOptionsModifier() mysqlDatabaseModifier {
 				InnoDBChangeBufferMaxSize:    linodego.Pointer(30),
 				InnoDBFlushNeighbors:         linodego.Pointer(1),
 				InnoDBFTMinTokenSize:         linodego.Pointer(3),
-				InnoDBFTServerStopwordTable:  DoublePointer(linodego.Pointer("mydb/stopwords")),
+				InnoDBFTServerStopwordTable:  linodego.DoublePointer("mydb/stopwords"),
 				InnoDBLockWaitTimeout:        linodego.Pointer(50),
 				InnoDBLogBufferSize:          linodego.Pointer(16777216),
 				InnoDBOnlineAlterLogMaxSize:  linodego.Pointer(134217728),