return unmodified plot with shade_*(NULL) (#567)

Author: simonpcouch

NEWS.md

@@ -1,5 +1,8 @@
 # infer (development version)
 
+* Fixed bug where adding `shade_confidence_interval(NULL)` or `shade_p_value(NULL)` 
+  to plots resulted in `list()` rather than the unmodified plot (#566).
+
 * Introduced support for arbitrary test statistics in `calculate()`. In addition
   to the pre-implemented `calculate(stat)` options, taken as strings, users can
   now supply a function defining any scalar-valued test statistic. See

R/shade_confidence_interval.R

@@ -162,11 +162,12 @@ shade_confidence_interval_term <- function(
   endpoints <- impute_endpoints(endpoints, plot, call = call)
   check_shade_confidence_interval_args(color, fill)
 
-  res <- list()
   if (is.null(endpoints)) {
-    return(res)
+    return(plot)
   }
 
+  res <- list()
+
   if (!is.null(fill)) {
     # Making extra step of precomputing arguments in order to have default value
     # of `alpha = 0.6` overwritable in `...`

R/shade_p_value.R

@@ -168,11 +168,12 @@ shade_p_value_term <- function(
 
   term <- x_axis_label(plot)
 
-  res <- list()
   if (is.null(obs_stat)) {
-    return(res)
+    return(plot)
   }
 
+  res <- list()
+
   # Add shading
   if (!is.null(direction) && !is.null(fill)) {
     if (direction %in% c("less", "left", "greater", "right")) {