Warn about unknown aesthetics & params.

Fixes #1585

Author: hadley

NEWS.md

@@ -1,4 +1,10 @@
 # ggplot2 2.1.0.9000 
+
+* When creating a layer, ggplot2 will warn if you use an unknown aesthetic
+  or an unknown parameter. Compared to the previous version, this is
+  stricter for aesthetics (previously there was no message), and less
+  strict for parameters (previously this threw an error) (#1585).
+
 * The facet system, as well as the internal panel class, has been rewritten in 
   ggproto. Facets are now extendable in the same manner as geoms, stats etc. and
   the manner in which this is done is described in the extension vignette. On 

R/layer.r

@@ -100,11 +100,28 @@ layer <- function(geom = NULL, stat = NULL,
   stat_params <- params[intersect(names(params), stat$parameters(TRUE))]
 
   all <- c(geom$parameters(TRUE), stat$parameters(TRUE), geom$aesthetics())
-  extra <- setdiff(names(params), all)
-  if (length(extra) > 0) {
-    stop("Unknown parameters: ", paste(extra, collapse = ", "), call. = FALSE)
+
+  # Warn about extra params and aesthetics
+  extra_param <- setdiff(names(params), all)
+  if (length(extra_param) > 0) {
+    warning(
+      "Ignoring unknown parameters: ", paste(extra_param, collapse = ", "),
+      call. = FALSE,
+      immediate. = TRUE
+    )
   }
 
+  extra_aes <- setdiff(names(mapping), c(geom$aesthetics(), stat$aesthetics()))
+  if (length(extra_aes) > 0) {
+    warning(
+      "Ignoring unknown aesthetics: ", paste(extra_aes, collapse = ", "),
+      call. = FALSE,
+      immediate. = TRUE
+    )
+  }
+
+
+
   ggproto("LayerInstance", Layer,
     geom = geom,
     geom_params = geom_params,

R/stat-.r

@@ -134,5 +134,10 @@ Stat <- ggproto("Stat",
       args <- union(args, self$extra_params)
     }
     args
+  },
+
+  aesthetics = function(self) {
+    c(union(self$required_aes, names(self$default_aes)), "group")
   }
+
 )

tests/testthat/test-layer.r

@@ -8,8 +8,12 @@ test_that("aesthetics go in aes_params", {
   expect_equal(l$aes_params, list(size = "red"))
 })
 
-test_that("unknown params create error", {
-  expect_error(geom_point(blah = "red"), "Unknown parameters")
+test_that("unknown params create warning", {
+  expect_warning(geom_point(blah = "red"), "unknown parameters")
+})
+
+test_that("unknown aesthietcs create warning", {
+  expect_warning(geom_point(aes(blah = "red")), "unknown aesthetics")
 })
 
 # Calculated aesthetics ---------------------------------------------------

tests/testthat/test-stat-bin.R

@@ -6,8 +6,13 @@ test_that("stat_bin throws error when y aesthetic present", {
   expect_error(ggplot_build(ggplot(dat, aes(x, y)) + stat_bin()),
     "must not be used with a y aesthetic.")
 
-  expect_error(p <- ggplot_build(ggplot(dat, aes(x)) + stat_bin(y = 5)),
-    "Unknown parameters: y")
+  expect_warning(
+    expect_error(
+      ggplot_build(ggplot(dat, aes(x)) + stat_bin(y = 5)),
+      "StatBin requires a continuous x"
+    ),
+    "unknown parameters: y"
+  )
 })
 
 test_that("bins specifies the number of bins", {
@@ -116,8 +121,8 @@ test_that("stat_count throws error when y aesthetic present", {
   expect_error(ggplot_build(ggplot(dat, aes(x, y)) + stat_count()),
     "must not be used with a y aesthetic.")
 
-  expect_error(p <- ggplot_build(ggplot(dat, aes(x)) + stat_count(y = 5)),
-    "Unknown parameters: y")
+  expect_warning(p <- ggplot_build(ggplot(dat, aes(x)) + stat_count(y = 5)),
+    "unknown parameters: y")
 })
 
 test_that("stat_count preserves x order for continuous and discrete", {