scale_colour_manual(palette=foo): cannot coerce type 'closure' to vector of type 'character'

[sjackman]

Using the palette argument of scale_colour_manual yields the error:
Error in as.vector(x, "character"): cannot coerce type 'closure' to vector of type 'character'

My apologies in advance if it's my error.

@th4ckl on Twitter says…

I don't think this works at the moment. palette is passed to manual_scale, but it looks like manual_scale always defines a new pal that is then passed on to discrete_scale. Looks like a bug to me.

https://twitter.com/th4ckl/status/1104207569034199040

Reprex

library(ggplot2)
library(Polychrome)

# Does not work.
alphabet_colors <- function(n) as.vector(Polychrome::alphabet.colors(n))
ggplot(diamonds, aes(x = carat, y = price, colour = clarity)) +
    geom_point() +
    scale_colour_manual(palette = alphabet_colors)
#> Error in as.vector(x, "character"): cannot coerce type 'closure' to vector of type 'character'

# Works!
ggplot(diamonds, aes(x = carat, y = price, colour = clarity)) +
    geom_point() +
    scale_colour_manual(values = as.vector(Polychrome::alphabet.colors(8)))

^{Created on 2019-03-09 by the reprex package (v0.2.1)}

[clauswilke]

I don't think scale_colour_manual() was ever meant to be used this way but I see that the documentation creates this impression. It would be fairly easy to fix this for the manual scales, but now I'm worrying that the problem exists for many other scales also. The fundamental problem is overly eager forwarding of arguments to discrete_scale().

library(ggplot2)
library(Polychrome)

# Does not work.
alphabet_colors <- function(n) as.vector(Polychrome::alphabet.colors(n))
ggplot(diamonds, aes(x = carat, y = price, colour = clarity)) +
  geom_point() +
  scale_colour_viridis_d(palette = alphabet_colors)
#> Error in as.vector(x, "character"): cannot coerce type 'closure' to vector of type 'character'

^{Created on 2019-03-10 by the reprex package (v0.2.1)}

[sjackman]

Settings values rather than palette works well enough for me. How is the palette argument meant to be used; is there an example in the documentation?

[clauswilke]

It's not meant to be used at all. The bug is that palette is accessible and mentioned in the documentation.

[sjackman]

Great. Thanks for the clarification. Feel free to close this issue if you like.

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