ggplot2 3.5.0+结合ggnewscale多分类填充图例异常求助

我维护着一个用ggplot2展示脑成像数据的R包ggbrain，该包依赖ggnewscale实现多图层复用fill映射。在ggplot2 3.5.0之前，通过在scale_fill_*中设置drop=FALSE、仅对需隐藏图例的图层设show.legend=FALSE，可保留分类图例的未使用因子水平。但ggplot2 3.5.0发布后，需设置show.legend=TRUE才能保留未使用水平，导致后续图层覆盖之前的设置，出现无意义的全黑图例。我已尝试用gginnards查看对象，也按官方建议指定show.legend参数，但均无效果。

案例1：设show.legend=NA时，缺失水平未被绘制 #

data1 <- expand.grid(dim1=1:10, dim2=1:10)
data1$value1 <- rnorm(100)

data2 <- expand.grid(dim1=1:10, dim2=1:10)
data2$value2 <- factor(sample(c(NA, "f1", "f2", "f3", "f4"), size = 100, replace=TRUE), levels = paste0("f", 1:5))

data3 <- expand.grid(dim1=1:10, dim2=1:10)
data3$value3 <- factor(sample(c(NA, "i1", "i2", "i3", "i4"), size = 100, replace=TRUE), levels = paste0("i", 1:5))

ggplot(mapping=aes(x=dim1, y=dim2)) +
  geom_raster(data=data1, mapping=aes(fill=value1), show.legend = FALSE) +
  scale_fill_gradient(low = "grey8", high = "grey92") +
  ggnewscale::new_scale_fill() +
  geom_raster(data=data2, mapping=aes(fill=value2), show.legend=NA) +
  scale_fill_brewer("layer2", palette = "Set3", drop=FALSE, na.value = "transparent", na.translate=FALSE) +
  ggnewscale::new_scale_fill() +
  geom_raster(data=data3, mapping=aes(fill=value3), show.legend = NA) +
  scale_fill_brewer("layer3", palette = "Dark2", drop=FALSE, na.value = "transparent", na.translate=FALSE)

案例2：按ggplot2 3.5.0+建议设show.legend=TRUE，破坏下层图层 #

ggplot(mapping=aes(x=dim1, y=dim2)) +
  geom_raster(data=data1, mapping=aes(fill=value1), show.legend = FALSE) + # 将变为fill_ggnewscale_2
  scale_fill_gradient(low = "grey8", high = "grey92") +
  ggnewscale::new_scale_fill() +
  geom_raster(data=data2, mapping=aes(fill=value2), show.legend=TRUE) +
  scale_fill_brewer("layer2", palette = "Set3", drop=FALSE, na.value = "transparent", na.translate=FALSE) + # 将变为fill_ggnewscale_1
  ggnewscale::new_scale_fill() +
  geom_raster(data=data3, mapping=aes(fill=value3), show.legend = TRUE) +
  scale_fill_brewer("layer3", palette = "Dark2", drop=FALSE, na.value = "transparent", na.translate=FALSE)

案例3：明确指定show.legend参数，仍无效果 #

ggplot(mapping=aes(x=dim1, y=dim2)) +
  geom_raster(data=data1, mapping=aes(fill=value1), show.legend = c(fill_ggnewscale_2=FALSE)) + # 将变为fill_ggnewscale_2
  scale_fill_gradient(low = "grey8", high = "grey92") +
  ggnewscale::new_scale_fill() +
  geom_raster(data=data2, mapping=aes(fill=value2), show.legend=c(fill_ggnewscale_1=TRUE)) +
  scale_fill_brewer("layer2", palette = "Set3", drop=FALSE, na.value = "transparent", na.translate=FALSE) + # 将变为fill_ggnewscale_1
  ggnewscale::new_scale_fill() +
  geom_raster(data=data3, mapping=aes(fill=value3), show.legend = c(fill=TRUE)) +
  scale_fill_brewer("layer3", palette = "Dark2", drop=FALSE, na.value = "transparent", na.translate=FALSE)

恳请各位提供解决建议！

内容的提问来源于stack exchange，提问作者Michael Hallquist