Add error message for predicting with untrained PipeOp or Graph

NEWS.md

@@ -1,5 +1,5 @@
 # mlr3pipelines 0.7.2-9000
-
+- Added missing error for predicting with untrained `PipeOp`s / `Graph`s.
 
 # mlr3pipelines 0.7.2
 

R/Graph.R

@@ -444,6 +444,7 @@ Graph = R6Class("Graph",
       self$edges[, c("src_id", "dst_id") := list(map_values(src_id, old, new), map_values(dst_id, old, new))]
       invisible(self)
     },
+
     update_ids = function(prefix = "", postfix = "") {
       ids = names2(self$pipeops)
       self$set_names(ids, sprintf("%s%s%s", assert_string(prefix), ids, assert_string(postfix)))
@@ -456,9 +457,13 @@ Graph = R6Class("Graph",
     },
 
     predict = function(input, single_input = TRUE) {
+      if (!self$is_trained) {
+        stop("Cannot predict, Graph has not been trained yet")
+      }
       graph_load_namespaces(self, "predict")
       graph_reduce(self, input, "predict", single_input)
     },
+
     help = function(help_type = getOption("help_type")) {
       parts = strsplit(self$man, split = "::", fixed = TRUE)[[1]]
       match.fun("help")(parts[[2]], package = parts[[1]], help_type = help_type)
@@ -717,7 +722,7 @@ graph_load_namespaces = function(self, info) {
 #' @export
 predict.Graph = function(object, newdata, ...) {
   if (!object$is_trained) {
-    stop("Graph is not trained.")
+    stop("Cannot predict, Graph has not been trained yet")
   }
   output = object$output
   if (nrow(output) != 1) {

R/PipeOp.R

@@ -188,7 +188,7 @@
 #'   should not modify the `PipeOp` in any way.\cr
 #'
 #' @section Inheriting:
-#' To create your own `PipeOp`, you need to overload the `private$.train()` and `private$.test()` functions.
+#' To create your own `PipeOp`, you need to overload the `private$.train()` and `private$.predict()` functions.
 #' It is most likely also necessary to overload the `$initialize()` function to do additional initialization.
 #' The `$initialize()` method should have at least the arguments `id` and `param_vals`, which should be passed on to `super$initialize()` unchanged.
 #' `id` should have a useful default value, and `param_vals` should have the default value `list()`, meaning no initialization of hyperparameters.
@@ -325,6 +325,10 @@ PipeOp = R6Class("PipeOp",
     predict = function(input) {
       assert_list(input, .var.name = sprintf("input to PipeOp %s's $predict()", self$id))
 
+      if (!self$is_trained) {
+        stopf("Cannot predict, PipeOp '%s' has not been trained yet", self$id)
+      }
+
       # need to load packages in train *and* predict, because they might run in different R instances
       require_namespaces(self$packages)
 

tests/testthat/test_Graph.R

@@ -666,3 +666,10 @@ test_that("Graph with vararg input", {
     list(debugvararg.output = 1006, debugvararg2.output = 2006))
 
 })
+
+test_that("Error when predicting with untrained Graph, #893", {
+  g = Graph$new()$
+    add_pipeop(PipeOpDebugBasic$new())
+
+  expect_error(g$predict(tsk("iris")), "Graph has not been trained yet")
+})

tests/testthat/test_PipeOp.R

@@ -13,6 +13,7 @@ test_that("PipeOp - General functions", {
   expect_equal(po_1$packages, "mlr3pipelines")
   expect_null(po_1$state)
   assert_subset(po_1$tags, mlr_reflections$pipeops$valid_tags)
+  expect_error(po_1$predict(list(tsk("iris"))), "has not been trained yet")
 
   expect_output(expect_equal(po_1$train(list(1)), list(output = 1)), "Training debug.basic")
   expect_equal(po_1$state, list(input = 1))
@@ -95,14 +96,16 @@ test_that("Informative error and warning messages", {
 
   expect_no_warning(suppressWarnings(gr$predict(tsk("iris"))))
 
-
   gr$param_set$values$classif.debug.warning_train = 0
   gr$param_set$values$classif.debug.warning_predict = 0
+
   gr$param_set$values$classif.debug.error_train = 1
-  gr$param_set$values$classif.debug.error_predict = 1
-
   expect_error(gr$train(tsk("iris")), "This happened PipeOp classif.debug's \\$train\\(\\)$")
 
+  gr$param_set$values$classif.debug.error_train = 0
+  gr$param_set$values$classif.debug.error_predict = 1
+  # Need to first train the Graph for predict to work
+  gr$train(tsk("iris"))
   expect_error(gr$predict(tsk("iris")), "This happened PipeOp classif.debug's \\$predict\\(\\)$")
 
   potest = R6::R6Class("potest", inherit = PipeOp,

tests/testthat/test_pipeop_ovr.R

@@ -67,6 +67,8 @@ test_that("PipeOpOVRUnite- train and predict", {
     lrn$train(task)
     lrn$predict(task)
   })
+  # Need to first train before predicting
+  expect_list(po$train(list(as.Multiplicity(NULL))), len = 1, types = "null")
   pout = po$predict(list(as.Multiplicity(tin)))
   expect_prediction_classif(pout[[1]])
 
@@ -112,6 +114,8 @@ test_that("PipeOpOVRSplit and PipeOpOVRUnite - train and predict", {
     lrn$train(task)
     lrn$predict(task)
   })
+  # Need to first train before predicting
+  po$train(list(as.Multiplicity(NULL)))
   pout_ref = po$predict(list(as.Multiplicity(tin)))
 
   gr = PipeOpOVRSplit$new() %>>% LearnerClassifRpart$new() %>>% PipeOpOVRUnite$new()