In ggplot2, is it possible to identify which aesthetics are set based on the ggplot build object?

In ggplot2, is it possible to identify which aesthetics are set based on the ggplot build object?

library(tidyverse)

p <- ggplot2::faithfuld |>
  ggplot() +
  geom_contour(aes(x = waiting, y = eruptions, z = density,
              col = after_stat(level)),
    bins = 8
  )

ggplot_build(p)$data[[1]] |> tibble()
#> # A tibble: 829 × 13
#>    colour  order level     x     y piece group     nlevel PANEL weight linewidth
#>    <chr>   <dbl> <dbl> <dbl> <dbl> <int> <fct>      <dbl> <fct>  <dbl>     <dbl>
#>  1 #132B43 0.005 0.005  74.7  5.1      1 -1-002-0…  0.143 1          1       0.5
#>  2 #132B43 0.005 0.005  74.5  5.09     1 -1-002-0…  0.143 1          1       0.5
#>  3 #132B43 0.005 0.005  73.9  5.05     1 -1-002-0…  0.143 1          1       0.5
#>  4 #132B43 0.005 0.005  73.8  5.05     1 -1-002-0…  0.143 1          1       0.5
#>  5 #132B43 0.005 0.005  73.3  5.01     1 -1-002-0…  0.143 1          1       0.5
#>  6 #132B43 0.005 0.005  73.1  4.99     1 -1-002-0…  0.143 1          1       0.5
#>  7 #132B43 0.005 0.005  72.7  4.96     1 -1-002-0…  0.143 1          1       0.5
#>  8 #132B43 0.005 0.005  72.4  4.92     1 -1-002-0…  0.143 1          1       0.5
#>  9 #132B43 0.005 0.005  72.3  4.91     1 -1-002-0…  0.143 1          1       0.5
#> 10 #132B43 0.005 0.005  71.9  4.86     1 -1-002-0…  0.143 1          1       0.5
#> # ℹ 819 more rows
#> # ℹ 2 more variables: linetype <dbl>, alpha <lgl>
ggplot_build(p)$layout
#> <ggproto object: Class Layout, gg>
#>     coord: <ggproto object: Class CoordCartesian, Coord, gg>
#>         aspect: function
#>         backtransform_range: function
#>         clip: on
#>         default: TRUE
#>         distance: function
#>         expand: TRUE
#>         is_free: function
#>         is_linear: function
#>         labels: function
#>         limits: list
#>         modify_scales: function
#>         range: function
#>         render_axis_h: function
#>         render_axis_v: function
#>         render_bg: function
#>         render_fg: function
#>         setup_data: function
#>         setup_layout: function
#>         setup_panel_guides: function
#>         setup_panel_params: function
#>         setup_params: function
#>         train_panel_guides: function
#>         transform: function
#>         super:  <ggproto object: Class CoordCartesian, Coord, gg>
#>     coord_params: list
#>     facet: <ggproto object: Class FacetNull, Facet, gg>
#>         compute_layout: function
#>         draw_back: function
#>         draw_front: function
#>         draw_labels: function
#>         draw_panels: function
#>         finish_data: function
#>         init_scales: function
#>         map_data: function
#>         params: list
#>         setup_data: function
#>         setup_params: function
#>         shrink: TRUE
#>         train_scales: function
#>         vars: function
#>         super:  <ggproto object: Class FacetNull, Facet, gg>
#>     facet_params: list
#>     finish_data: function
#>     get_scales: function
#>     layout: data.frame
#>     map_position: function
#>     panel_params: list
#>     panel_scales_x: list
#>     panel_scales_y: list
#>     render: function
#>     render_labels: function
#>     reset_scales: function
#>     resolve_label: function
#>     setup: function
#>     setup_panel_guides: function
#>     setup_panel_params: function
#>     train_position: function
#>     super:  <ggproto object: Class Layout, gg>

Created on 2023-08-25 with reprex v2.0.2

geom: <ggproto object: Class GeomContour, GeomPath, Geom, gg>

this can be dug out of str(g)

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