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Bug? Strange behavior when using geom_ribbon with ggplotly() in R

Dear all,

today I encountered unexpected behavior of plotly when using it from R. I want to plot the uncertainty region around a time series forecast using geom_ribbon. This is why my data has two columsn - one for the upper, one for the lower end of the region - which I pad with NAs until the forecast horizon starts. In regular ggplots the ribbon is thus invisible as long as upper and lower point is NA, but not so in plotly. A reproducible example below:

y <- rnorm(144, 0, 2)

y_comp <- data.frame(mean = y,
                     x = 1:144,
                     upper = c(rep(NA, (130)), y[131:144]+3),
                     lower = c(rep(NA, (130)), y[131:144]-3)

p <- ggplot(y_comp, aes(x = x, y = mean, ymin = lower, ymax = upper)) + geom_line() +
  geom_ribbon(alpha = .25)


Which gives:

Is this expected behavior, or a bug?