fix: task's cbind works with non-standard pk (#1079)

NEWS.md

@@ -5,10 +5,11 @@
 * refactor: Optimize runtime of setting row roles.
 * refactor: Optimize runtime of marshalling.
 * refactor: Optimize runtime of `Task$col_info`
+* fix: `Task$cbind()` now works with non-standard primary keys
+  for `data.frames` (#961).
 * fix: Triggering of fallback learner now has log-level "info"
   instead of "debug" (#972)
 
-
 # mlr3 0.20.2
 
 * refactor: Move RhpcBLASctl to suggest.

R/Task.R

@@ -562,8 +562,11 @@ Task = R6Class("Task",
           return(invisible(self))
         }
 
-        row_ids = if (pk %in% names(data)) pk else self$row_ids
-        data = as_data_backend(data, primary_key = row_ids)
+        row_ids = if (pk %nin% names(data)) {
+          data[[pk]] = self$row_ids
+        }
+
+        data = as_data_backend(data, primary_key = pk)
       } else {
         assert_backend(data)
         if (data$ncol <= 1L) {

tests/testthat/test_Task.R

@@ -634,3 +634,11 @@ test_that("divide requires ratio in (0, 1)", {
 test_that("divide requires ids to be row_ids", {
   expect_error(tsk("iris")$divide(ids = 0.5))
 })
+
+test_that("cbind supports non-standard primary key (#961)", {
+  tbl = data.table(x = runif(10), y = runif(10), myid = 1:10)
+  b = as_data_backend(tbl, primary_key = "myid")
+  task = as_task_regr(b, target = "y")
+  task$cbind(data.table(x1 = 10:1))
+  expect_true("x1" %in% task$feature_names)
+})