highlight() function: setting the 'off' event to 'plotly_unhover' results in an error.

This is a modified example from here:

library(plotly)

# load the `txhousing` dataset
data(txhousing, package = "ggplot2")

# declare `city` as the SQL 'query by' column
tx <- highlight_key(txhousing, ~city)

# initiate a plotly object
base <- plot_ly(tx, color = I("black")) %>% 
  group_by(city)

# create a time series of median house price
time_series <- base %>%
  group_by(city) %>%
  add_lines(x = ~date, y = ~median)

highlight(
  time_series, 
  on = "plotly_hover",
  off = "plotly_hover", # causes error
  selectize = FALSE, 
  dynamic = FALSE,
  color = "red",
  persistent = FALSE
)

Not providing off results in a warning:

Setting the off event (i.e., 'plotly_doubleclick') to match the on event (i.e., 'plotly_hover'). You can change this default via the highlight() function.

Setting off to plotly_hover or plotly_unhover (my initial intention) results in an error:

Error in match.arg(off, off_options) :
'arg' should be one of “plotly_doubleclick”, “plotly_deselect”, “plotly_relayout”

Found this via: https://stackoverflow.com/a/64387370/9841389

PS: using the latest CRAN version of plotly.

从 highlight() 入口点开始，复现将 off 设置为 plotly_hover 和 plotly_unhover 的修改版 txhousing 示例。检查 off_options 验证，并将其与文档所述的事件行为进行比较；完成的标准是，有效的 off 事件不再引发所报告的 match.arg 错误，并且示例按预期运行。