Fix #2467: multi-aesthetic scales now show legend and split traces correctly

When a scale has multiple aesthetics (e.g., aesthetics = c("colour", "fill")),
the discreteScales registry now stores each aesthetic separately instead of
combining them with "_". This ensures that "colour_plotlyDomain" matches
discreteScales[["colour"]] for proper trace splitting and legend generation.

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

Author: cpsievert

R/layers2traces.R

@@ -78,11 +78,15 @@ layers2traces <- function(data, prestats_data, layout, p) {
   }, data, hoverTextAes)
 
   # draw legends only for discrete scales
+  # Register each aesthetic separately for proper legend matching (fixes #2467)
+  # When a scale has multiple aesthetics (e.g., c("colour", "fill")), we need
+  # individual entries so "colour_plotlyDomain" matches discreteScales[["colour"]]
   discreteScales <- list()
   for (sc in p$scales$non_position_scales()$scales) {
     if (sc$is_discrete()) {
-      nm <- paste(sc$aesthetics, collapse = "_")
-      discreteScales[[nm]] <- sc
+      for (aes_name in sc$aesthetics) {
+        discreteScales[[aes_name]] <- sc
+      }
     }
   }
   # Convert "high-level" geoms to their "low-level" counterpart

tests/testthat/test-ggplot-color.R

@@ -17,7 +17,25 @@ test_that("scale_*_manual with unused aesthetics does not error (#2466)", {
       aesthetics = c("colour", "fill")
     )
   # Should not error with "undefined columns selected"
-  # (Note: trace splitting with multi-aesthetic scales is a separate issue #2467)
   expect_error(plotly_build(ggplotly(p)), NA)
 })
 
+test_that("multi-aesthetic scales show legend and split traces correctly (#2467)", {
+  # When scale has aesthetics = c('colour', 'fill') and both are used,
+  # traces should be split by the variable and legend should appear
+  p <- ggplot(iris, aes(Sepal.Length, Sepal.Width, colour = Species, fill = Species)) +
+    geom_point(shape = 21) +
+    scale_colour_manual(
+      values = c("setosa" = "red", "versicolor" = "blue", "virginica" = "green"),
+      aesthetics = c("colour", "fill")
+    )
+  L <- plotly_build(ggplotly(p))$x
+  # Should have 3 traces (one per Species level)
+  expect_equal(length(L$data), 3)
+  # Should show legend
+  expect_true(any(sapply(L$data, function(d) isTRUE(d$showlegend))))
+  # Trace names should be the species names
+  trace_names <- sapply(L$data, function(d) d$name)
+  expect_true(all(c("setosa", "versicolor", "virginica") %in% trace_names))
+})
+