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fix: learners can handle new factor levels #1403

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Merged
merged 1 commit into from
Oct 10, 2025
Merged

fix: learners can handle new factor levels #1403

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7 changes: 6 additions & 1 deletion R/assertions.R
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Original file line number Diff line number Diff line change
Expand Up @@ -207,7 +207,12 @@ assert_predictable = function(task, learner) {
predict_type = fget_keys(task$col_info, i = ids, j = "type", key = "id")
predict_levels = fget_keys(task$col_info, i = ids, j = "levels", key = "id")

ok = all(train_type == predict_type) && all(pmap_lgl(list(x = train_levels, y = predict_levels), identical))

ok = all(train_type == predict_type)

if ("new_levels" %nin% learner$properties) {
ok = ok && all(pmap_lgl(list(x = train_levels, y = predict_levels), identical))
}

if (!ok) {
stopf("Learner '%s' received task with different column info (feature type or factor level ordering) during train and predict.", learner$id)
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13 changes: 13 additions & 0 deletions tests/testthat/test_Learner.R
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Expand Up @@ -1015,3 +1015,16 @@ test_that("config error does not trigger callback", {
l$encapsulate("evaluate", lrn("classif.featureless"))
expect_error(l$train(tsk("iris")), regexp = "You misconfigured the learner")
})

test_that("new_levels property is working", {
learner = lrn("classif.featureless")
task = tsk("penguins")
learner$train(task)
data = task$data()
set(data, i = 1L, j = "island", value = "NewIsland")

expect_error(learner$predict_newdata(data), "received task with different column info")

learner$properties = c(learner$properties, "new_levels")
expect_prediction(learner$predict_newdata(data))
})