Apparent Inconsistency Between `Facet$setup_data` and `Facet$finish_data` usage

[brodieG]

Facet$setup_data is called by Layout with all of the plot and layer data, as seen in Layout$Setup:

    data <- c(list(plot_data), data)

    # Setup facets
    self$facet_params <- self$facet$setup_params(data, self$facet$params)
    self$facet_params$plot_env <- plot_env
    data <- self$facet$setup_data(data, self$facet_params)

However, Facet$finish_data is called repeatedly with each layer data in Layout$finish_data:

  finish_data = function(self, data) {
    lapply(data, self$facet$finish_data,
      layout = self$layout,
      x_scales = self$panel_scales_x,
      y_scales = self$panel_scales_y,
      params = self$facet_params
    )
  }

Since Facet is somewhat orthogonal to the layers (or at least applies to all the layers), it feels that the treatment in setup_data is more appropriate.

It may be too late to change this, but I imagine usage of this method is rare enough that fixing it (assuming you agree this ideally would be fixed) might not be too painful in terms of breaking existing code.

[teunbrand]

Thanks for this suggestion, I agree that it would make a nice symmetry in methods.
However, unless a practical need arises I don't think we should proceed this with this as it would break some extensions.