legendrank scrambled by fillcolor with type='scatter'

Expected behavior

When making a stacked area chart, the ordering of the legend values follows the ordering of the legendrank argument.

Actual behavior

When making a stacked area chart, the ordering of the legend values depends on the legendrank argument in combination with the alphabetical ordering of the fillcolor argument. Somehow the fillcolors seem to be scrambling the order.

Here's an example:

# The goal is to make a stacked area chart, where each fill color is a severity
# level. Then, the legend should be ordered by severity
library(plotly)

severities = c('Mild', 'Moderate', 'Severe')
severity_colors = c('#FF0000', '#440000', '#AA0000')
# ^ colors chosen specifically to be out of alphabetical order
severity_color_dict = setNames(severity_colors, severities)

timeline = data.frame(Time = rep(1:15, 3),
                      coverage = rep(1, 45),
                      Severity = factor(rep(severities, each = 15)))
timeline$fill = severity_color_dict[timeline$Severity]

# default order
plot_ly(timeline, x = ~Time, y = ~coverage, name = ~Severity, type = 'scatter',
        mode = 'none', stackgroup = 'one', groupnorm = '')

# add fillcolor-- now the legend is in alphabetical order of fillcolor
plot_ly(timeline, x = ~Time, y = ~coverage, name = ~Severity, type = 'scatter',
        mode = 'none', stackgroup = 'one', groupnorm = '', fillcolor = ~fill)

# this should be ordered by Severity, but it's still in alphabetical order of
# fillcolor
plot_ly(timeline, x = ~Time, y = ~coverage, name = ~Severity, type = 'scatter',
        mode = 'none', stackgroup = 'one', groupnorm = '', fillcolor = ~fill,
        legendrank = ~as.integer(Severity))

# The intended order can only be acheived by using the alphabetical ordering of
# the fill colors to "unscramble" the legendrank
unscramble_dict = order(severity_colors)
plot_ly(timeline, x = ~Time, y = ~coverage, name = ~Severity, type = 'scatter',
        mode = 'none', stackgroup = 'one', groupnorm = '', fillcolor = ~fill,
        legendrank = ~unscramble_dict[as.integer(Severity)])

Session info

R version 4.1.2 (2021-11-01)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 22.04.2 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3
LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.20.so

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8     LC_MONETARY=en_US.UTF-8   
 [6] LC_MESSAGES=en_US.UTF-8    LC_PAPER=en_US.UTF-8       LC_NAME=C                  LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] plotly_4.10.2 ggplot2_3.4.2

loaded via a namespace (and not attached):
 [1] magrittr_2.0.3    tidyselect_1.2.0  munsell_0.5.0     viridisLite_0.4.2 colorspace_2.1-0  R6_2.5.1          rlang_1.1.1      
 [8] fastmap_1.1.1     fansi_1.0.4       httr_1.4.6        dplyr_1.1.2       tools_4.1.2       parallel_4.1.2    grid_4.1.2       
[15] data.table_1.14.8 gtable_0.3.3      utf8_1.2.3        cli_3.6.1         withr_2.5.0       ellipsis_0.3.2    crosstalk_1.2.0  
[22] htmltools_0.5.5   yaml_2.3.7        lazyeval_0.2.2    digest_0.6.31     tibble_3.2.1      lifecycle_1.0.3   tidyr_1.3.0      
[29] purrr_1.0.1       htmlwidgets_1.6.2 vctrs_0.6.2       glue_1.6.2        compiler_4.1.2    pillar_1.9.0      generics_0.1.3   
[36] scales_1.2.1      jsonlite_1.8.5    pkgconfig_2.0.3  

首先运行使用 plot_ly 以及 type='scatter'、stackgroup、fillcolor 和 legendrank 的可复现 R 示例。跟踪堆叠面积图的图例顺序如何响应这些参数；完成标准是无论 fillcolor 的顺序如何，图例顺序都始终遵循 legendrank，同时保留已报告的行为。