Rework case_when() on top of vctrs::vec_case_when() (#7727)

* Rework `case_when()` on top of `vctrs::vec_case_when()`

* NEWS

* Bring over a few tests from `vec_case_when()`

* Switch from `cases` to `conditions` to match vctrs

Author: DavisVaughan

NEWS.md

@@ -29,9 +29,10 @@
 
   The recycling behavior that allows this style of `case_when()` to work is unsafe, and can result in silent bugs that we'd like to guard against with an error in the future (#7082).
 
-* The following vector functions have gotten significantly faster and use much less memory due to a rewrite in C via vctrs (#7723):
+* The following vector functions have gotten significantly faster and use much less memory due to a rewrite in C via vctrs (#7723, #7725, #7727):
 
   * `if_else()`
+  * `case_when()`
   * `coalesce()`
 
 * `if_else()` no longer allows `condition` to be a logical array. It must be a logical vector with no `dim` attribute (#7723).

R/case-match.R

@@ -168,30 +168,24 @@ vec_case_match <- function(
   obj_check_list(haystacks, arg = haystacks_arg, call = call)
   list_check_all_vectors(haystacks, arg = haystacks_arg, call = call)
 
-  if (length(haystacks) == 0L) {
-    # `case_match()` is like `case_when()` and doesn't allow empty `...`,
-    # even though `vec_case_when()` is well defined for this case.
-    abort("At least one condition must be supplied.", call = call)
-  }
-
   haystacks <- vec_cast_common(
     !!!haystacks,
     .to = needles,
     .arg = haystacks_arg,
     .call = call
   )
 
-  cases <- map(haystacks, vec_in, needles = needles)
+  conditions <- map(haystacks, vec_in, needles = needles)
 
   size <- vec_size(needles)
 
-  vctrs::vec_case_when(
-    cases = cases,
+  vec_case_when(
+    conditions = conditions,
     values = values,
     default = default,
     ptype = ptype,
     size = size,
-    cases_arg = "",
+    conditions_arg = "",
     values_arg = values_arg,
     default_arg = default_arg,
     error_call = call

R/case-when.R

@@ -170,20 +170,20 @@ case_when <- function(..., .default = NULL, .ptype = NULL, .size = NULL) {
   )
 
   # Only recycle `conditions`. Expect that `vec_case_when()` requires all
-  # `conditions` to be the same size, but can efficiently recycle `values`
-  # at the C level without extra allocations.
+  # `conditions` to be the same size, but can efficiently recycle `values` at
+  # the C level without extra allocations.
   conditions <- vec_recycle_common(!!!conditions, .size = .size)
 
   vec_case_when(
     conditions = conditions,
     values = values,
-    conditions_arg = "",
-    values_arg = "",
     default = .default,
-    default_arg = ".default",
     ptype = .ptype,
     size = .size,
-    call = current_env()
+    conditions_arg = "",
+    values_arg = "",
+    default_arg = ".default",
+    error_call = current_env()
   )
 }
 
@@ -335,6 +335,10 @@ case_formula_evaluate <- function(args, default_env, dots_env, error_call) {
   n_args <- length(args)
   seq_args <- seq_len(n_args)
 
+  if (n_args == 0L) {
+    abort("At least one condition must be supplied.", call = error_call)
+  }
+
   pairs <- map2(
     .x = args,
     .y = seq_args,

R/coalesce.R

@@ -73,12 +73,12 @@ coalesce <- function(..., .ptype = NULL, .size = NULL) {
   values <- args$values
   default <- args$default
 
-  cases <- map(values, function(value) {
+  conditions <- map(values, function(value) {
     !vec_detect_missing(value)
   })
 
-  vctrs::vec_case_when(
-    cases = cases,
+  vec_case_when(
+    conditions = conditions,
     values = values,
     default = default,
     ptype = .ptype,

R/utils.R

@@ -8,6 +8,11 @@ paste_line <- function(...) {
   paste(chr(...), collapse = "\n")
 }
 
+vec_paste0 <- function(...) {
+  args <- vec_recycle_common(...)
+  exec(paste0, !!!args)
+}
+
 # Until vctrs::new_data_frame() forwards row names automatically
 dplyr_new_data_frame <- function(
   x = data.frame(),

R/vec-case-when.R

@@ -14,14 +14,6 @@
       Error in `case_match()`:
       ! At least one condition must be supplied.
 
----
-
-    Code
-      vec_case_match(1, haystacks = list(), values = list())
-    Condition
-      Error in `vec_case_match()`:
-      ! At least one condition must be supplied.
-
 # `.default` is part of common type computation
 
     Code