formula-driven symbol ?bug?

[timelyportfolio]

I discovered this as I was assembling this Plotly + statebins post. I am not convinced it is a bug yet, but it is certainly very confusing to me. While I experienced this behavior with symbol, I am guessing that it extends to other arguments, such as color, x, etc. If I had to choose I would say the behavior in the last example is closest to what I would expect, but of course using add_markers instead of the add_trace.

library(plotly)
df <- data.frame( x = 1:10 )

doesn't work

# doesn't work
df %>%
  plot_ly() %>%
  add_markers(
    x = ~x, y = ~x,
    symbol = ~1:nrow(df) > 5,
    symbols = c("triangle-down","triangle-up"),
    size = I(200)
  )

works

# works
df %>%
  plot_ly() %>%
  add_markers(
    x = ~x, y = ~x,
    symbol = c(rep("a",5),rep("b",5)),
    symbols = c("triangle-down","triangle-up"),
    size = I(200)
  )

works

# works
df %>%
  plot_ly() %>%
  add_markers(
    x = ~x, y = ~x,
    symbol = c(rep("triangle-down",5),rep("triangle-up",5)),
    symbols = c("triangle-down","triangle-up"),
    size = I(200)
  )

works

# works
df %>%
  plot_ly() %>%
  add_trace(
    x = ~x, y = ~x,
    type = "scatter",
    mode = "markers",
    marker = list(
      symbol = ~ifelse(1:nrow(df) > 5, "triangle-down", "triangle-up")
    ),
    size = I(200)
  )