Fix #2455, #2460: element_blank panel.border no longer creates empty shapes

The make_panel_border() function now checks if panel.border is NULL or
element_blank before processing. This prevents creating useless invisible
shapes when themes like theme_grey() or theme_classic() have blank borders.

Themes with visible borders (like theme_bw()) continue to work correctly.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cpsievert

R/ggplotly.R

@@ -1389,7 +1389,12 @@ make_strip_rect <- function(xdom, ydom, theme, side = "top") {
 
 # theme(panel.border) -> plotly.js rect shape
 make_panel_border <- function(xdom, ydom, theme) {
-  rekt <- rect2shape(theme[["panel.border"]])
+  border <- theme[["panel.border"]]
+  # Don't draw anything if panel.border is blank or NULL
+  if (is.null(border) || is_blank(border)) {
+    return(list())
+  }
+  rekt <- rect2shape(border)
   rekt$x0 <- xdom[1]
   rekt$x1 <- xdom[2]
   rekt$y0 <- ydom[1]

tests/testthat/test-ggplot-theme.R

@@ -65,12 +65,28 @@ test_that("marker default shape is a circle", {
 test_that("plot panel border is translated correctly", {
   ggpenguin <- penguin.base + theme_grey() # has no panel.border
   info <- expect_doppelganger_built(ggpenguin, "theme-panel-border-1")
-  
+
   red <- ggplot(palmerpenguins::penguins) +
     theme_grey() +
     geom_point(aes(bill_length_mm, bill_depth_mm)) +
     theme(panel.border = element_rect(colour = "red", fill = NA))
-  
+
   info <- expect_doppelganger_built(red, "theme-panel-border-2")
   expect_true(info$layout$shapes[[1]]$line$color == toRGB("red"))
 })
+
+test_that("element_blank panel.border does not create empty shapes (#2455, #2460)", {
+  # theme_grey() has element_blank() panel.border - should NOT create a shape
+  p_grey <- ggplot(mtcars, aes(wt, mpg)) + geom_point() + theme_grey()
+  L_grey <- plotly_build(ggplotly(p_grey))$x
+  # No panel border shapes should be created for element_blank
+  grey_shapes <- Filter(function(s) identical(s$xref, "paper") && identical(s$yref, "paper"), L_grey$layout$shapes)
+  expect_equal(length(grey_shapes), 0)
+
+  # theme_bw() has visible panel.border - SHOULD create a shape
+  p_bw <- ggplot(mtcars, aes(wt, mpg)) + geom_point() + theme_bw()
+  L_bw <- plotly_build(ggplotly(p_bw))$x
+  bw_shapes <- Filter(function(s) identical(s$xref, "paper") && identical(s$yref, "paper"), L_bw$layout$shapes)
+  expect_true(length(bw_shapes) > 0)
+  expect_false(is.na(bw_shapes[[1]]$line$color))
+})