move finalizers to private

DESCRIPTION

@@ -21,7 +21,7 @@ Depends:
     mlr3 (>= 0.13.0),
     R (>= 3.1.0)
 Imports:
-    R6,
+    R6 (>= 2.4.0),
     backports,
     checkmate,
     data.table,

R/DataBackendDplyr.R

@@ -120,16 +120,6 @@ DataBackendDplyr = R6Class("DataBackendDplyr", inherit = DataBackend, cloneable
       self$connector = assert_function(connector, args = character(), null.ok = TRUE)
     },
 
-    #' @description
-    #' Finalizer which disconnects from the database.
-    #' This is called during garbage collection of the instance.
-    #' @return `logical(1)`, the return value of [DBI::dbDisconnect()].
-    finalize = function() {
-      if (isTRUE(self$valid)) {
-        DBI::dbDisconnect(private$.data$src$con)
-      }
-    },
-
     #' @description
     #' Returns a slice of the data.
     #' Calls [dplyr::filter()] and [dplyr::select()] on the table and converts it to a [data.table::data.table()].
@@ -271,6 +261,16 @@ DataBackendDplyr = R6Class("DataBackendDplyr", inherit = DataBackend, cloneable
   ),
 
   private = list(
+    # @description
+    # Finalizer which disconnects from the database.
+    # This is called during garbage collection of the instance.
+    # @return `logical(1)`, the return value of [DBI::dbDisconnect()].
+    finalize = function() {
+      if (isTRUE(self$valid)) {
+        DBI::dbDisconnect(private$.data$src$con)
+      }
+    },
+
     .calculate_hash = function() {
       private$.reconnect()
       calculate_hash(private$.data)

R/DataBackendDuckDB.R

@@ -73,16 +73,6 @@ DataBackendDuckDB = R6Class("DataBackendDuckDB", inherit = DataBackend, cloneabl
 
     },
 
-    #' @description
-    #' Finalizer which disconnects from the database.
-    #' This is called during garbage collection of the instance.
-    #' @return `logical(1)`, the return value of [DBI::dbDisconnect()].
-    finalize = function() {
-      if (isTRUE(self$valid)) {
-        DBI::dbDisconnect(private$.data, shutdown = TRUE)
-      }
-    },
-
     #' @description
     #' Returns a slice of the data.
     #'
@@ -243,6 +233,16 @@ DataBackendDuckDB = R6Class("DataBackendDuckDB", inherit = DataBackend, cloneabl
   ),
 
   private = list(
+    # @description
+    # Finalizer which disconnects from the database.
+    # This is called during garbage collection of the instance.
+    # @return `logical(1)`, the return value of [DBI::dbDisconnect()].
+    finalize = function() {
+      if (isTRUE(self$valid)) {
+        DBI::dbDisconnect(private$.data, shutdown = TRUE)
+      }
+    },
+
     .calculate_hash = function() {
       private$.reconnect()
       calculate_hash(private$.data@driver@dbdir)

tests/testthat/helper.R

@@ -29,7 +29,7 @@ disconnect.SQLiteConnection = function(x) {
 registerS3method("disconnect", "SQLiteConnection", disconnect.SQLiteConnection)
 
 disconnect.DataBackend = function(x) {
-  x$finalize()
+  mlr3misc::get_private(x)$finalize()
 }
 registerS3method("disconnect", "DataBackend", disconnect.DataBackend)