refactor: raise structured errors instead of bare stop() (#198)

* refactor: raise structured errors instead of bare stop()

`CLAUDE.md` mandates `cli` for errors, but eleven places raised a plain
`simpleError`. They use the `mlr3misc` condition constructors now, which
format with `cli` and carry an `Mlr3Error` class that callers can catch.

* Update FSelector.R

Author: be-marc

R/EnsembleFSResult.R

@@ -214,7 +214,7 @@ EnsembleFSResult = R6Class(
 
       # check if `inner_measure` is an `mlr3::Measure`
       if (which == "inner" && is.null(private$.inner_measure)) {
-        stop("No inner_measure was defined during initialization")
+        error_input("No `inner_measure` was defined during initialization.")
       }
 
       private$.active_measure = which

R/FSelector.R

@@ -96,7 +96,7 @@ FSelector = R6Class(
     #' Set of control parameters.
     param_set = function(rhs) {
       if (!missing(rhs) && !identical(rhs, private$.param_set)) {
-        stop("$param_set is read-only.")
+        error_input("`$param_set` is read-only.")
       }
       private$.param_set
     },
@@ -106,7 +106,7 @@ FSelector = R6Class(
     #' Must be a subset of [`mlr_reflections$fselect_properties`][mlr3::mlr_reflections].
     properties = function(rhs) {
       if (!missing(rhs) && !identical(rhs, private$.properties)) {
-        stop("$properties is read-only.")
+        error_input("`$properties` is read-only.")
       }
       private$.properties
     },
@@ -116,7 +116,7 @@ FSelector = R6Class(
     #' Note that these packages will be loaded via [requireNamespace()], and are not attached.
     packages = function(rhs) {
       if (!missing(rhs) && !identical(rhs, private$.packages)) {
-        stop("$packages is read-only.")
+        error_input("`$packages` is read-only.")
       }
       private$.packages
     },
@@ -126,7 +126,7 @@ FSelector = R6Class(
     #' Can be used in tables, plot and text output instead of the ID.
     label = function(rhs) {
       if (!missing(rhs) && !identical(rhs, private$.param_set)) {
-        stop("$label is read-only.")
+        error_input("`$label` is read-only.")
       }
       private$.label
     },
@@ -136,14 +136,14 @@ FSelector = R6Class(
     #' The referenced help package can be opened via method `$help()`.
     man = function(rhs) {
       if (!missing(rhs) && !identical(rhs, private$.man)) {
-        stop("$man is read-only.")
+        error_input("`$man` is read-only.")
       }
       private$.man
     }
   ),
 
   private = list(
-    .optimize = function(inst) stop("abstract"),
+    .optimize = function(inst) error_bbotk("`.optimize()` is abstract and must be implemented by the subclass."),
 
     .assign_result = function(inst) {
       assert_fselect_instance(inst)

R/FSelectorAsyncFromOptimizerAsync.R

@@ -53,7 +53,7 @@ FSelectorAsyncFromOptimizerAsync = R6Class(
     #' Set of control parameters.
     param_set = function(rhs) {
       if (!missing(rhs) && !identical(rhs, private$.optimizer$param_set)) {
-        stop("$param_set is read-only.")
+        error_input("`$param_set` is read-only.")
       }
       private$.optimizer$param_set
     }

R/FSelectorBatchSequential.R

@@ -66,7 +66,7 @@ FSelectorBatchSequential = R6Class(
     optimization_path = function(inst, include_uhash = FALSE) {
       archive = inst$archive
       if (archive$n_batch == 0L) {
-        stop("No results stored in archive")
+        error_input("No results stored in the archive.")
       }
       uhash = if (include_uhash) "uhash" else NULL
       res = archive$data[, head(.SD, 1), by = get("batch_nr")]

R/FSelectorBatchShadowVariableSearch.R

@@ -78,7 +78,7 @@ FSelectorBatchShadowVariableSearch = R6Class(
     #' @return [data.table::data.table]
     optimization_path = function(inst) {
       if (inst$archive$n_batch == 0L) {
-        stop("No results stored in archive")
+        error_input("No results stored in the archive.")
       }
 
       # we have to use the best method to get the same tie breaking as in the optimize method
@@ -128,7 +128,7 @@ FSelectorBatchShadowVariableSearch = R6Class(
           if (any(as.logical(res[, shadow_variables, with = FALSE]))) {
             # stop if the first selected feature is a shadow variable
             if (archive$n_batch == 1) {
-              stop("The first selected feature is a shadow variable.")
+              error_mlr3("The first selected feature is a shadow variable.")
             }
 
             # remove last batch with selected shadow variable from archive

tests/testthat/test_embedded_ensemble_fselect.R

@@ -52,7 +52,7 @@ test_that("embedded efs works", {
   )
 
   # cannot change to use inner_measure
-  expect_error(efsr$set_active_measure(which = "inner"), "No inner_measure was defined")
+  expect_error(efsr$set_active_measure(which = "inner"), "No `inner_measure` was defined")
   # changing to "outer" leaves us with the same measure
   efsr$set_active_measure(which = "outer")
   expect_equal(efsr$measure$id, "classif.ce") # classification error

tests/testthat/test_mlr_fselectors.R

@@ -19,6 +19,16 @@ test_that("as.data.table objects parameter", {
   expect_list(tab$object, "FSelector", any.missing = FALSE)
 })
 
+test_that("read-only bindings of a fselector raise a structured error", {
+  fselector = fs("random_search")
+
+  expect_error(fselector$param_set <- ps(), class = "Mlr3ErrorInput")
+  expect_error(fselector$properties <- "single-crit", class = "Mlr3ErrorInput")
+  expect_error(fselector$packages <- "mlr3", class = "Mlr3ErrorInput")
+  expect_error(fselector$label <- "other", class = "Mlr3ErrorInput")
+  expect_error(fselector$man <- "other", class = "Mlr3ErrorInput")
+})
+  
 test_that("reloading the package does not duplicate reflections", {
   bbotk_reflections = utils::getFromNamespace("bbotk_reflections", ns = "bbotk")
   mlr_reflections = utils::getFromNamespace("mlr_reflections", ns = "mlr3")