Error in validate_guide() when not attaching ggraph

[gdagstn]

Hi,

I have a peculiar use case which triggers an error that I do not know how to address. Not sure if this can be really considered a bug, but I thought I'd report it anyway.

I want to use ggraph in a package where I have listed it as an optional dependency in Suggests, so rather than having the package and its functions imported to the NAMESPACE, I am calling the functions directly using ggraph::ggraph().

However, this triggers what I can only understand as some sort of conflict between ggraph and ggplot2 when I try to define a colour scale for edges.

Consider this reprex:

# Loading these packages as they are imported by the package
library(igraph)
library(ggplot2)

gr = make_graph("zachary")

# Mock up numeric attributes to mimic my use case
E(gr)$weight = runif(length(E(gr)))
E(gr)$prop = runif(length(E(gr)))
V(gr)$type = sample(c("A", "B", "C"), size = length(V(gr)), replace = TRUE)
V(gr)$name = paste0(V(gr)$type, V(gr))  

ggraph::ggraph(gr, layout = "fr") + 
  ggraph::geom_edge_link(aes(edge_color = .data[["weight"]], 
                                                     alpha = .data[["prop"]]), 
                                                     width = 1,
                                                     arrow = grid::arrow(length = unit(4, 'mm')),
                                                     end_cap = ggraph::circle(3, 'mm')) + 
  ggraph::geom_node_point(aes(color = .data[["type"]]), size = 3) + 
  ggraph::geom_node_text(aes(label = .data[["name"]])) +
  ggraph::scale_edge_color_continuous()

Error in `validate_guide()`:
! Unknown guide: edge_colourbar
Run `rlang::last_trace()` to see where the error occurred.

validate_guide() is a ggplot2 internal, and in fact last_trace() gives:

---
Backtrace:
     ▆
  1. ├─base (local) `<fn>`(x)
  2. └─ggplot2:::print.ggplot(x)
  3.   ├─ggplot2::ggplot_build(x)
  4.   ├─ggraph:::ggplot_build.ggraph(x)
  5.   ├─base::NextMethod()
  6.   └─ggplot2:::ggplot_build.ggplot(x)
  7.     └─plot$guides$build(npscales, plot$layers, plot$labels, data)
  8.       └─ggplot2 (local) build(..., self = self)
  9.         └─self$setup(scales, aesthetics = aesthetics)
 10.           └─ggplot2 (local) setup(..., self = self)
 11.             └─base::lapply(...)
 12.               └─ggplot2 (local) FUN(X[[i]], ...)
 13.                 └─ggplot2:::validate_guide(guide)
Run rlang::last_trace(drop = FALSE) to see 2 hidden frames.

Note that if I remove the ggraph::scale_edge_color_continuous() line, the plot works:

ggraph::ggraph(gr, layout = "fr") + 
  ggraph::geom_edge_link(aes(edge_color = .data[["weight"]], 
                                                     alpha = .data[["prop"]]), 
                                                     width = 1,
                                                     arrow = grid::arrow(length = unit(4, 'mm')),
                                                     end_cap = ggraph::circle(3, 'mm')) + 
  ggraph::geom_node_point(aes(color = .data[["type"]]), size = 3) + 
  ggraph::geom_node_text(aes(label = .data[["name"]]))

But it is clearly not what I want to do. Similarly, if I attach ggraph the code works, but that means adding it as a dependency, which I would like to avoid if possible.

Is there anything that can be done other than attaching ggraph?

Thanks in advance!

[m-delem]

Same context and same issue here!

[teunbrand]

Thanks for the report. This seems to me to be the same as #133.