Improve facet error messages in animint2dir

R/facet-layout.r

@@ -93,8 +93,22 @@ layout_base <- function(data, vars = NULL, drop = TRUE) {
 
   # Form the base data frame which contains all combinations of facetting
   # variables that appear in the data
-  has_all <- unlist(plyr::llply(values, length)) == length(vars)
+  has_all <- unlist(lapply(values, length)) == length(vars)
   if (!any(has_all)) {
+    all_data_vars <- unique(unlist(lapply(data, names)))
+    missing_vars <- setdiff(names(vars)[names(vars) != "."], all_data_vars)
+    if (length(missing_vars) > 0) {
+      stop(sprintf(
+        "Facet variable%s not found in data: %s\nAvailable columns: %s\nUse string notation like facet_wrap(\"var\") instead of formula notation facet_wrap(. ~ var)",
+        if (length(missing_vars) > 1) "s" else "",
+        paste(missing_vars, collapse = ", "),
+        paste(all_data_vars, collapse = ", ")
+      ))
+    }
+    # Reached when all facet variables exist somewhere in the data, but no
+    # single layer has all of them together. For example, facet_grid(X ~ Y)
+    # where layer 1 only has column X and layer 2 only has column Y — neither
+    # layer alone satisfies all facetting variables, so has_all is FALSE for every layer.
     stop("At least one layer must contain all variables used for facetting")
   }
 

R/z_animintHelpers.R

@@ -1097,4 +1097,4 @@ selectSSandCS <- function(aesthetics_list){
   }
   ## TODO: how to handle showSelected$ignored in prev animint code??
   return(aes.list)
-}
+}

tests/testthat/test-renderer-facet-error-messages.R

@@ -0,0 +1,34 @@
+acontext("Facet error messages")
+test_that("facet_wrap formula with missing variable gives clear error", {
+  viz <- list(
+    scatter = ggplot() +
+      facet_wrap(. ~ NonExistentColumn) +
+      geom_point(aes(Sepal.Length, Petal.Length), data = iris)
+  )
+  expect_error(
+    animint2dir(viz, out.dir = tempfile(), open.browser = FALSE),
+    "Facet variable not found in data: NonExistentColumn\nAvailable columns: Sepal.Length, Sepal.Width, Petal.Length, Petal.Width, Species\nUse string notation like facet_wrap(\"var\") instead of formula notation facet_wrap(. ~ var)",
+    fixed = TRUE
+  )
+})
+test_that("facet_grid formula with missing variable gives clear error", {
+  viz <- list(
+    scatter = ggplot() +
+      facet_grid(. ~ MissingVar) +
+      geom_point(aes(Sepal.Length, Petal.Length), data = iris)
+  )
+  expect_error(
+    animint2dir(viz, out.dir = tempfile(), open.browser = FALSE),
+    "Facet variable not found in data: MissingVar\nAvailable columns: Sepal.Length, Sepal.Width, Petal.Length, Petal.Width, Species\nUse string notation like facet_wrap(\"var\") instead of formula notation facet_wrap(. ~ var)",
+    fixed = TRUE
+  )
+})
+test_that("facet_wrap string notation works", {
+  viz <- list(
+    scatter = ggplot() +
+      facet_wrap("Species") +
+      geom_point(aes(Sepal.Length, Petal.Length), data = iris)
+  )
+  info <- animint2dir(viz, out.dir = tempfile(), open.browser = FALSE)
+  expect_true(file.exists(file.path(info$out.dir, "index.html")))
+})