Discrete scales cannot handle continuous values

[yutannihilation]

It seems discrete scales cannot handle continuous values with the current master (the CRAN version works).

When I ran tests on my local, I saw some warnings around here:

ggplot2/tests/testthat/test-scale-discrete.R

Lines 51 to 61 in 141c775

	test_that("discrete ranges also encompass continuous values", {
	df <- data_frame(x1 = c("a", "b", "c"), x2 = c(0, 2, 4), y = 1:3)
	base <- ggplot(df, aes(y = y)) + scale_x_discrete()
	x_range <- function(x) {
	layer_scales(x)$x$dimension()
	}
	expect_equal(x_range(base + geom_point(aes(x1))), c(1, 3))
	expect_equal(x_range(base + geom_point(aes(x2))), c(0, 4))

#> Warning in structure(in_domain, pos = match(in_domain, breaks)): Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
#>   Consider 'structure(list(), *)' instead.

For a simple example:

library(ggplot2)

df <- data.frame(x = c(0, 2, 4), y = 1:3, stringsAsFactors = FALSE)

ggplot(df, aes(x, y)) +
  geom_point() +
  scale_x_discrete()
#> Warning in structure(in_domain, pos = match(in_domain, breaks)): Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
#>   Consider 'structure(list(), *)' instead.

#> Warning in structure(in_domain, pos = match(in_domain, breaks)): Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
#>   Consider 'structure(list(), *)' instead.
#> Error in UseMethod("rescale"): no applicable method for 'rescale' applied to an object of class "list"

^{Created on 2019-07-30 by the reprex package (v0.3.0)}

Session info

devtools::session_info()
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[yutannihilation]

It seems the change was introduced by #3426.

[yutannihilation]

self$range$range can be NULL because train() is bypassed when is.discrete() returns FALSE.

ggplot2/R/scale-discrete-.r

Lines 77 to 83 in 141c775

	train = function(self, x) {
	if (is.discrete(x)) {
	self$range$train(x, drop = self$drop, na.rm = !self$na.translate)
	} else {
	self$range_c$train(x)
	}
	},

So, to fix this minimally, we can change the line 91 to self$range$range %||% integer():

ggplot2/R/scale-discrete-.r

Lines 85 to 97 in 141c775

	get_limits = function(self) {
	if (self$is_empty()) {
	c(0, 1)
	} else if (!is.null(self$limits) & !is.function(self$limits)){
	self$limits
	} else if (is.null(self$limits)) {
	self$range$range
	} else if (is.function(self$limits)) {
	self$limits(self$range$range)
	} else {
	integer(0)
	}
	},

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/