Better scale messages

[teunbrand]

This PR aims to fix #4185, fix #4258 and fix #1312.

Briefly, this PR sets the call field of a Scale ggproto class to a more informative call, and uses that call in the messaging.

Less brief: errors thrown in scales led to some confusion about which scale was throwing the error. Getting the appropriate call for every scale helps in throwing more informative messages. In addition, this PR deprecates the scale_name argument to scale constructors, as the call takes over its function. This is in opposition to suggested approach here: #1312 (comment). Some selected examples follow.

Previously, the below would throw:

Error: Continuous value supplied to discrete scale

Note that now it mentions the scale, and which values are unexpected.

devtools::load_all("~/packages/ggplot2")
#> ℹ Loading ggplot2

# See #4258
ggplot() + 
  geom_point(aes(x = "A", y = 2)) +
  scale_x_continuous()
#> Error in `scale_x_continuous()`:
#> ! Discrete values supplied to continuous scale
#> ℹ Example values: "A"

Previously the following would throw the very awkward:

#> Warning in log(x, base): NaNs produced
#> Warning: Transformation introduced infinite values in discrete y-axis

Now it mentions the correct scale and the transformation.

# See #4185
ggplot() +
  geom_point(aes(1, 1, colour = -1)) +
  scale_colour_viridis_c(trans = "log10")
#> Warning in log(x, base): NaNs produced
#> Warning in scale_colour_viridis_c(trans = "log10"): 
#> log-10 transformation introduced infinite values.

I also passed down some calls to several checkers, which previously simply didn't mention the scale.

scale_alpha_continuous(breaks = 1:2, labels = "A")
#> Error in `scale_alpha_continuous()`:
#> ! `breaks` and `labels` must have the same length

^{Created on 2023-07-04 with reprex v2.0.2}

Lastly, I also have an alternate reason for this PR. If we'd ever want to solve #4269, we'd need to know which parameters we're allowed to override. For example, if the user provides limits in a proper scale, but not breaks, we should be allowed to override the breaks (and maybe limits). In any case, we'd need to figure out what arguments were user supplied. This is now a lot easier:

scale <- scale_colour_discrete(breaks = c("A", "B", "C"), name = "My Scale")
call_args_names(scale$call)
#> [1] "breaks" "name"

[thomasp85]

Not hugely important but shouldn't these reference self$call as well

[teunbrand]

These don't have self as an argument, so I was hesitant about this. Should I give them self as an argument?

[thomasp85]

same as above

[thomasp85]

Apart from the few comments LGTM

[teunbrand]

I'm merging this despite Thomas' comments (to be fair, 'not hugely important' eerily looks like 'good enough').
The messages that currently lack a reported call are mostly developer-facing, and users should never see these.
Combined with a mild reluctance on my part to change the function signature: I'm happy with this as-is.

[averissimo]

I think this change created a problem when calling scale_y_continous within another package function via the double colon pkg::example_fun(...).

as.character(call[[1]]) contents is of length 3 and makes the if clause fails.

# [1] "::"         "tern"       "g_lineplot"

I created issue #5436