Merge pull request #956 from epiforecasts/fix-printing-issue

Remove function that resulted in an error when called from within print.data.table()

R/class-forecast.R

@@ -272,17 +272,27 @@ is_forecast <- function(x) {
   #   undesired situation if we set ...length() > 1
   # is.data.table: when [.data.table returns an atomic vector, it's clear it
   #   cannot be a valid forecast object, and it is likely intended by the user
-  if (data.table::is.data.table(out) && !is_dt_force_print) {
+
+  # in addition, we also check for a maximum length. The reason is that
+  # print.data.table will internally subset the data.table before printing.
+  # this subsetting triggers the validation, which is not desired in this case.
+  # this is a hack and ideally, we'd do things differently.
+  if (nrow(out) > 30 && data.table::is.data.table(out) && !is_dt_force_print) {
     # check whether subset object passes validation
     validation <- try(
       assert_forecast(forecast = out, verbose = FALSE),
       silent = TRUE
     )
     if (inherits(validation, "try-error")) {
       cli_warn(
+        #nolint start: keyword_quote_linter
         c(
-          "!" = "Error in validating forecast object: {validation}"
+          "!" = "Error in validating forecast object: {validation}.",
+          "i" = "Note this error is sometimes related to `data.table`s `print`.
+          Run {.help [{.fun assert_forecast}](scoringutils::assert_forecast)}
+          to confirm."
         )
+        #nolint end
       )
     }
   }

tests/testthat/test-class-forecast-nominal.R

@@ -53,3 +53,18 @@ test_that("get_metrics.forecast_nominal() works as expected", {
     is.list(get_metrics(example_nominal))
   )
 })
+
+
+# ==============================================================================
+# Printing
+# ==============================================================================
+test_that("Printing works as expected", {
+  suppressMessages(
+    expect_message(
+      expect_message(
+        capture.output(print(example_nominal)),
+        "Forecast type: nominal"
+      ),
+      "Forecast unit:")
+  )
+})

tests/testthat/test-class-forecast.R

@@ -146,14 +146,14 @@ test_that("print() works on forecast_* objects", {
 test_that("print() throws the expected messages", {
   test <- data.table::copy(example_point)
   class(test) <- c("point", "forecast", "data.table", "data.frame")
-  expect_warning(
-    suppressMessages(
-      expect_message(
-        capture.output(print(test)),
-        "Could not determine forecast type due to error in validation."
-      )
-    ),
-    "Error in validating"
+
+  # note that since introducing a length maximum for validation to be triggered,
+  # we don't throw a warning automatically anymore
+  suppressMessages(
+    expect_message(
+      capture.output(print(test)),
+      "Could not determine forecast type due to error in validation."
+    )
   )
 
   class(test) <- c("forecast_point", "forecast")