Ensure LayerSf is stateless wrt legend type determination

Author: thomasp85

R/layer-sf.R

@@ -32,6 +32,12 @@ layer_sf <- function(geom = NULL, stat = NULL,
 }
 
 LayerSf <- ggproto("LayerSf", Layer,
+  legend_key_type = NULL,
+
+  # This field carry state throughout rendering but will always be
+  # calculated before use
+  computed_legend_key_type = NULL,
+
   setup_layer = function(self, data, plot) {
     # process generic layer setup first
     data <- ggproto_parent(Layer, self)$setup_layer(data, plot)
@@ -50,24 +56,31 @@ LayerSf <- ggproto("LayerSf", Layer,
     # automatically determine the legend type
     if (is.null(self$legend_key_type)) {
       # first, set default value in case downstream tests fail
-      self$geom_params$legend <- "polygon"
+      self$computed_legend_key_type <- "polygon"
 
       # now check if the type should not be polygon
       if (!is.null(self$computed_mapping$geometry) && quo_is_symbol(self$computed_mapping$geometry)) {
         geometry_column <- as_name(self$computed_mapping$geometry)
         if (inherits(data[[geometry_column]], "sfc")) {
           sf_type <- detect_sf_type(data[[geometry_column]])
           if (sf_type == "point") {
-            self$geom_params$legend <- "point"
+            self$computed_legend_key_type <- "point"
           } else if (sf_type == "line") {
-            self$geom_params$legend <- "line"
+            self$computed_legend_key_type <- "line"
           }
         }
       }
     } else {
-      self$geom_params$legend <- self$legend_key_type
+      self$computed_legend_key_type <- self$legend_key_type
     }
     data
+  },
+  compute_geom_1 = function(self, data) {
+    data <- ggproto_parent(Layer, self)$compute_geom_1(data)
+
+    # Add legend type after computed_geom_params has been calculated
+    self$computed_geom_params$legend <- self$computed_legend_key_type
+    data
   }
 )
 

tests/testthat/test-geom-sf.R

@@ -33,23 +33,23 @@ test_that("geom_sf() determines the legend type automatically", {
 
   # test the automatic choice
   expect_identical(fun_geom_sf(mp, TRUE)$plot$layers[[1]]$show.legend, TRUE)
-  expect_identical(fun_geom_sf(mp, TRUE)$plot$layers[[1]]$geom_params$legend, "point")
+  expect_identical(fun_geom_sf(mp, TRUE)$plot$layers[[1]]$computed_geom_params$legend, "point")
 
   expect_identical(fun_geom_sf(mls, TRUE)$plot$layers[[1]]$show.legend, TRUE)
-  expect_identical(fun_geom_sf(mls, TRUE)$plot$layers[[1]]$geom_params$legend, "line")
+  expect_identical(fun_geom_sf(mls, TRUE)$plot$layers[[1]]$computed_geom_params$legend, "line")
 
   expect_identical(fun_geom_sf(mpol, TRUE)$plot$layers[[1]]$show.legend, TRUE)
-  expect_identical(fun_geom_sf(mpol, TRUE)$plot$layers[[1]]$geom_params$legend, "polygon")
+  expect_identical(fun_geom_sf(mpol, TRUE)$plot$layers[[1]]$computed_geom_params$legend, "polygon")
 
   # test that automatic choice can be overridden manually
   expect_identical(fun_geom_sf(mp, "point")$plot$layers[[1]]$show.legend, TRUE)
-  expect_identical(fun_geom_sf(mp, "point")$plot$layers[[1]]$geom_params$legend, "point")
+  expect_identical(fun_geom_sf(mp, "point")$plot$layers[[1]]$computed_geom_params$legend, "point")
 
   expect_identical(fun_geom_sf(mls, "point")$plot$layers[[1]]$show.legend, TRUE)
-  expect_identical(fun_geom_sf(mls, "point")$plot$layers[[1]]$geom_params$legend, "point")
+  expect_identical(fun_geom_sf(mls, "point")$plot$layers[[1]]$computed_geom_params$legend, "point")
 
   expect_identical(fun_geom_sf(mpol, "point")$plot$layers[[1]]$show.legend, TRUE)
-  expect_identical(fun_geom_sf(mpol, "point")$plot$layers[[1]]$geom_params$legend, "point")
+  expect_identical(fun_geom_sf(mpol, "point")$plot$layers[[1]]$computed_geom_params$legend, "point")
 })
 
 test_that("geom_sf() determines the legend type from mapped geometry column", {
@@ -70,19 +70,19 @@ test_that("geom_sf() determines the legend type from mapped geometry column", {
   p <- ggplot_build(
     ggplot(d_sf) + geom_sf(aes(geometry = g_point, colour = "a"))
   )
-  expect_identical(p$plot$layers[[1]]$geom_params$legend, "point")
+  expect_identical(p$plot$layers[[1]]$computed_geom_params$legend, "point")
 
   p <- ggplot_build(
     ggplot(d_sf) + geom_sf(aes(geometry = g_line, colour = "a"))
   )
-  expect_identical(p$plot$layers[[1]]$geom_params$legend, "line")
+  expect_identical(p$plot$layers[[1]]$computed_geom_params$legend, "line")
 
   # If `geometry` is not a symbol, `LayerSf$setup_layer()` gives up guessing
   # the legend type, and falls back to "polygon"
   p <- ggplot_build(
     ggplot(d_sf) + geom_sf(aes(geometry = identity(g_point), colour = "a"))
   )
-  expect_identical(p$plot$layers[[1]]$geom_params$legend, "polygon")
+  expect_identical(p$plot$layers[[1]]$computed_geom_params$legend, "polygon")
 })
 
 test_that("geom_sf() removes rows containing missing aes", {