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)
  )

Inizia eseguendo l’esempio R fornito con n=3, quindi varia n e confronta le larghezze delle barre e la visibilità in modalità overlay tra le due tracce. Analizza la gestione di barre e Date in plotly.R utilizzata da questo esempio e considera conclusa l’issue quando le tracce Date sparse mantengono larghezze appropriate e un singolo valore viene renderizzato senza richiedere date fittizie con valore zero.