Faster list2(), and deprecate rlang_env_dots_values() and rlang_env_dots_list()

NEWS.md

@@ -1,5 +1,7 @@
 # rlang (development version)
 
+* `list2()` is now a little faster (#1837).
+
 * New `%&&%` operator that returns RHS when LHS is non-NULL (#1774, @snystrom).
 
 * C code no longer calls `memcpy()` and `memset()` on 0-length R object memory

R/dots.R

@@ -88,16 +88,7 @@ NULL
 #'
 #' @export
 list2 <- function(...) {
-  .Call(
-    ffi_dots_list,
-    frame_env = environment(),
-    named = NULL,
-    ignore_empty = "trailing",
-    preserve_empty = FALSE,
-    unquote_names = TRUE,
-    homonyms = "keep",
-    check_assign = FALSE
-  )
+  .External2(ffi_list2)
 }
 #' @rdname list2
 #' @usage NULL

src/internal/cnd-handlers.c

@@ -7,6 +7,9 @@
 r_obj* ffi_try_fetch(r_obj* try_fetch_args) {
   r_obj* env = r_node_cadr(try_fetch_args);
 
+  // TODO: `rlang_env_dots_list()` will always clone `handlers`
+  // on the way out, and we could probably avoid that by switching
+  // to or creating another variant that doesn't clone.
   r_obj* handlers = KEEP(rlang_env_dots_list(env));
   r_env_poke(env, rlang_syms.handlers, handlers);
 

src/internal/dots.c

@@ -957,6 +957,8 @@ r_obj* ffi_dots_values(r_obj* args) {
   return out;
 }
 
+// Deprecated
+// Used by vctrs <= 0.6.5, so can't easily remove.
 // [[ export() ]]
 r_obj* rlang_env_dots_values(r_obj* env) {
   return dots_values_impl(env,
@@ -969,6 +971,8 @@ r_obj* rlang_env_dots_values(r_obj* env) {
                           false);
 }
 
+// Deprecated
+// Used by vctrs <= 0.6.5, so can't easily remove.
 // [[ export() ]]
 r_obj* rlang_env_dots_list(r_obj* env) {
   r_obj* out = KEEP(dots_values_impl(env,
@@ -979,12 +983,28 @@ r_obj* rlang_env_dots_list(r_obj* env) {
                                      rlang_objs_keep,
                                      r_false,
                                      true));
+  // Deprecated due to this clone being unnecessary.
+  // `rlang_env_dots_list()` has the exact same defaults as `list2()`, and
+  // `list2()` avoids the clone, so in vctrs we now just use that instead.
   out = r_vec_clone_shared(out);
 
   FREE(1);
   return out;
 }
 
+// Specialization for maximum performance via `External2()`, which is a little
+// faster than `.Call()` and gives us `frame_env` for free rather than needing
+// an R level `environment()` call
+r_obj* ffi_list2(r_obj* call, r_obj* op, r_obj* args, r_obj* frame_env) {
+  return dots_values_impl(frame_env,
+                          r_null,
+                          rlang_objs_trailing,
+                          r_false,
+                          r_true,
+                          rlang_objs_keep,
+                          r_false,
+                          true);
+}
 r_obj* ffi_dots_list(r_obj* frame_env,
                      r_obj* named,
                      r_obj* ignore_empty,

src/internal/internal.c

@@ -346,6 +346,7 @@ static const R_ExternalMethodDef externals[] = {
   {"ffi_exec",                          (DL_FUNC) &ffi_exec, 2},
   {"ffi_tilde_eval",                    (DL_FUNC) &ffi_tilde_eval, 3},
   {"ffi_try_fetch",                     (DL_FUNC) &ffi_try_fetch, 1},
+  {"ffi_list2",                         (DL_FUNC) &ffi_list2, 0},
   {NULL, NULL, 0}
 };
 
@@ -387,8 +388,6 @@ void R_init_rlang(DllInfo* dll) {
   R_RegisterCCallable("rlang", "rlang_xxh3_64bits",            (DL_FUNC) &XXH3_64bits);
 
   // Maturing
-  R_RegisterCCallable("rlang", "rlang_env_dots_list",          (DL_FUNC) &rlang_env_dots_list);
-  R_RegisterCCallable("rlang", "rlang_env_dots_values",        (DL_FUNC) &rlang_env_dots_values);
   R_RegisterCCallable("rlang", "rlang_is_splice_box",          (DL_FUNC) &is_splice_box);
   R_RegisterCCallable("rlang", "rlang_obj_encode_utf8",        (DL_FUNC) &obj_encode_utf8);
   R_RegisterCCallable("rlang", "rlang_str_as_symbol",          (DL_FUNC) &r_str_as_symbol);
@@ -399,6 +398,10 @@ void R_init_rlang(DllInfo* dll) {
   // Experimental
   R_RegisterCCallable("rlang", "rlang_squash_if",              (DL_FUNC) &r_squash_if);
 
+  // Deprecated
+  R_RegisterCCallable("rlang", "rlang_env_dots_list",          (DL_FUNC) &rlang_env_dots_list);
+  R_RegisterCCallable("rlang", "rlang_env_dots_values",        (DL_FUNC) &rlang_env_dots_values);
+
   // Compatibility
   R_RegisterCCallable("rlang", "rlang_as_data_mask",           (DL_FUNC) &ffi_as_data_mask_compat);
   R_RegisterCCallable("rlang", "rlang_new_data_mask",          (DL_FUNC) &ffi_new_data_mask_compat);