Call for feature: supporting of expressions

When I try use expression object as lab labels, ggplotly raises an error.

p <- ggplot(data=de$table, aes(x=logFC, y=-log10(PValue), colour=threshold)) +
        geom_point(size=1.75, alpha = 0.4) +
        # ylim(c(0, input$ylmslider)) +
        xlab(expression("log"[2]*"(Fold Change)")) + ylab(expression("-log"[10]*"(p-value)")) +
        geom_vline(xintercept = 0, colour = "grey",
  linetype = "dashed", size = 2) + # add line at 0
        geom_hline(yintercept = -log10(0.05), colour = "grey",
  linetype = "dashed", size = 2) + theme(legend.position = "none") # p(0.05) = 1.3
#> Everything is ok up to now
ggplotly(p)
#> Error in unique.default(x) : unimplemented type 'expression' in 'HashTableSetup'

You can reproduce this scenario by using any expression as axis titles.

首先使用提供的 ggplotly 示例和 expression 轴标题重现该问题。跟踪 ggplotly 如何处理这些标签，然后验证同一图形能够在不出现 HashTableSetup 错误的情况下完成转换，并且 expression 标签得到保留。