Non-orthogonal coords preserve AsIs x/y variables (#6206)

* exempt some coords from transforming x/y AsIs variables

* add tests

* add news bullet

* throw warning when only one of two variables is AsIs

* update snapshot

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* In non-orthogonal coordinate systems (`coord_sf()`, `coord_polar()` and 
+  `coord_radial()`), using 'AsIs' variables escape transformation when
+  both `x` and `y` is an 'AsIs' variable (@teunbrand, #6205).
 * The following methods have been deprecated: `fortify.lm()`, `fortify.glht()`,
   `fortify.confint.glht()`, `fortify.summary.glht()` and `fortify.cld()`. It
   is recommend to use `broom::augment()` and `broom::tidy()` instead 

R/coord-.R

@@ -284,3 +284,24 @@ check_coord_limits <- function(
   check_object(limits, is_vector, "a vector", arg = arg, call = call)
   check_length(limits, 2L, arg = arg, call = call)
 }
+
+is_transform_immune <- function(data, coord_name) {
+  x <- inherits(data$x, "AsIs")
+  y <- inherits(data$y, "AsIs")
+  if (!(x || y)) {
+    # Neither variable is AsIs, so we need to transform
+    return(FALSE)
+  }
+  if (x && y) {
+    # Both variables are AsIs, so no need to transform
+    return(TRUE)
+  }
+  # We're now in the `xor(x, y)` case
+  var <- if (x) "x" else "y"
+  alt <- if (x) "y" else "x"
+  cli::cli_warn(
+    "{.fn {coord_name}} cannot respect the {.cls AsIs} class of {.var {var}} \\
+    when {.var {alt}} is not also {.cls AsIs}."
+  )
+  return(FALSE)
+}

R/coord-polar.R

@@ -180,6 +180,10 @@ CoordPolar <- ggproto("CoordPolar", Coord,
   },
 
   transform = function(self, data, panel_params) {
+    if (is_transform_immune(data, snake_class(self))) {
+      return(data)
+    }
+
     arc  <- self$start + c(0, 2 * pi)
     dir  <- self$direction
     data <- rename_data(self, data)

R/coord-radial.R

@@ -275,6 +275,10 @@ CoordRadial <- ggproto("CoordRadial", Coord,
   },
 
   transform = function(self, data, panel_params) {
+    if (is_transform_immune(data, snake_class(self))) {
+      return(data)
+    }
+
     data <- rename_data(self, data)
     bbox <- panel_params$bbox %||% list(x = c(0, 1), y = c(0, 1))
     arc  <- panel_params$arc  %||% c(0, 2 * pi)

R/coord-sf.R

@@ -77,6 +77,10 @@ CoordSf <- ggproto("CoordSf", CoordCartesian,
   },
 
   transform = function(self, data, panel_params) {
+    if (is_transform_immune(data, snake_class(self))) {
+      return(data)
+    }
+
     # we need to transform all non-sf data into the correct coordinate system
     source_crs <- panel_params$default_crs
     target_crs <- panel_params$crs

tests/testthat/_snaps/coord-polar.md

@@ -12,3 +12,7 @@
     No appropriate placement found for `r_axis_inside`.
     i Axis will be placed at panel edge.
 
+# when both x and y are AsIs, they are not transformed
+
+    `coord_radial()` cannot respect the <AsIs> class of `x` when `y` is not also <AsIs>.
+

tests/testthat/test-coord-polar.R

@@ -155,6 +155,31 @@ test_that("bounding box calculations are sensible", {
   )
 })
 
+test_that("when both x and y are AsIs, they are not transformed", {
+
+  p <- ggplot() +
+    annotate("text", x = I(0.75), y = I(0.25), label = "foo") +
+    scale_x_continuous(limits = c(0, 10)) +
+    scale_y_continuous(limits = c(0, 10))
+
+  grob <- get_layer_grob(p + coord_polar())[[1]]
+  location <- c(as.numeric(grob$x), as.numeric(grob$y))
+  expect_equal(location, c(0.75, 0.25))
+
+  grob <- get_layer_grob(p + coord_radial())[[1]]
+  location <- c(as.numeric(grob$x), as.numeric(grob$y))
+  expect_equal(location, c(0.75, 0.25))
+
+  # Check warning is thrown if only one is AsIs
+  p <- ggplot() +
+    annotate("text", x = I(0.75), y = 2.5, label = "foo") +
+    scale_x_continuous(limits = c(0, 10)) +
+    scale_y_continuous(limits = c(0, 10)) +
+    coord_radial()
+
+  expect_snapshot_warning(ggplotGrob(p))
+
+})
 
 # Visual tests ------------------------------------------------------------
 

tests/testthat/test-coord_sf.R

@@ -314,6 +314,22 @@ test_that("sf_transform_xy() works", {
 
 })
 
+test_that("when both x and y are AsIs, they are not transformed", {
+
+  skip_if_not_installed("sf")
+
+  p <- ggplot() +
+    annotate("text", x = I(0.75), y = I(0.25), label = "foo") +
+    scale_x_continuous(limits = c(-180, 180)) +
+    scale_y_continuous(limits = c(-80, 80)) +
+    coord_sf(default_crs = 4326, crs = 3857)
+
+  grob <- get_layer_grob(p)[[1]]
+  location <- c(as.numeric(grob$x), as.numeric(grob$y))
+  expect_equal(location, c(0.75, 0.25))
+
+})
+
 test_that("coord_sf() can use function breaks and n.breaks", {
 
   polygon <- sf::st_sfc(