Problems with barcharts with barmode='overlay' and Date objects

I need to plot several barcharts with Date objects on the x-axis with barmode = 'overlay' for a whole year. When there are enough values to plot, everything works fine, as I would like the bars to have equal widths along all traces.

But when one trace has few elements, the width of those traces are expanded.
And when one trace only has 1 value, it is not shown at all.

I could overcome those problems by creating fictional Dates with 0 y-values for the rest of the year, but I was hoping there is a better way of solving that.

The variable n in the example can be used to determine the amount of bars for the problematic
trace.

library(plotly)
n = 3

## All days of 2019 ###############
Days2019 <- data.frame(
  date = seq(as.Date("2019-01-01"), as.Date("2019-12-31"), by = "days")
)

## Sample n Days of 2019 ###############
df <- data.frame(
  date = sort(sample(Days2019$date, size = n, replace = F)),
  val = sample(1:100, n, replace = T)
)

## Merge fictional 0 y-Values #################
# df = merge(df, Days2019, by="date", all=T)
# df[is.na(df$val),]$val=0

## Sample 30 Days of 2019 ###############
holiday1 <- data.frame(
  date = sort(sample(Days2019$date, size = 30, replace = F))
)

## Plot Plotly ###############
maxY = max(df$val)
plot_ly() %>%
  add_trace(data = holiday1, x = ~date, y = maxY, marker = list(color = "gray"), type="bar", name="Holidays") %>% 
  add_trace(data = df, x = ~date, y = ~val, marker = list(color = "red"), type="bar", name="Values") %>% 
  plotly::layout(autosize = F,
                 barmode = 'overlay',
                 bargap = 0.05,
                 xaxis = list(
                   type = "date",
                   range = c(as.Date("2019-01-01")-1,
                             as.Date("2019-12-31")+1),
                   autorange = FALSE,
                   tickmode = "auto",
                   nticks = 14L,
                   automargin = F)
  )

首先运行提供的 R 示例并设置 n=3，然后改变 n，比较两条 trace 之间在 overlay 模式下的条形宽度和可见性。跟踪此示例所使用的 plotly.R 对 bar 和 Date 的处理，并在稀疏的 Date trace 保持适当宽度且单个值无需虚构的零值日期即可渲染时，视为 issue 完成。