scattermapbox non-circle marker symbols not shown in legend since v4.12.0

Start with the supplied R reprex using scattermapbox traces and compare the legend behavior between plotly 4.11.0 and 4.12.0. Trace how marker symbols are passed through add_trace and inspect the scattermapbox legend handling; done means circle, diamond, square, and marker entries render correctly without affecting scattergeo or scatter behavior.

Since upgrading to plotly 4.12.0, only the "circle" symbol is rendered correctly in the legend for scattermapbox traces. Other marker symbols (e.g. "diamond", "square") are no longer displayed — the legend shows a blank entry for those.

v 4.12.0

v 4.11.0

(note that already in previuos versions, the non-circle markers were not shown on the canvas itself, but this was not an issue in our use case, because we only wanted to create the custom legend with the square markers)

reprex

library(plotly)

symbols_to_try <- c(
  "circle",
  "diamond",
  "square",
  "marker"
)

traces <- lapply(seq_along(symbols_to_try), function(i) {
  list(
    type       = "scattermapbox",
    mode       = "markers",
    lon        = i * 2,
    lat        = 51,
    name       = symbols_to_try[i],
    showlegend = TRUE,
    hoverinfo  = "name",
    marker     = list(
      color  = "steelblue",
      size   = 20,
      symbol = symbols_to_try[i]
    )
  )
})

p <- plotly_empty() |>
  layout(
    mapbox = list(
      style  = "carto-positron",
      center = list(lon = 5, lat = 51),
      zoom   = 3
    ),
    legend = list(x = 1, xanchor = "right", y = 1)
  ) |>
  config(displaylogo = FALSE)

for (tr in traces) {
  p <- add_trace(p,
    inherit    = FALSE,
    type       = tr$type,
    mode       = tr$mode,
    lon        = tr$lon,
    lat        = tr$lat,
    name       = tr$name,
    showlegend = tr$showlegend,
    hoverinfo  = tr$hoverinfo,
    marker     = tr$marker
  )
}

p

packageVersion("plotly")

Further info:

The legend (and markers on canvas) work fine with "scattergeo" or even "scatter", but it has other side-effects in our setting that makes the plot be drawn twice, even if setting the layout like

plotly::layout(
    plotly_object,
    geo = list(
      visible = FALSE,
      showframe = FALSE,
      showcoastlines = FALSE,
      showland = FALSE,
      showocean = FALSE
    )
  )