Remove dependency on R_NamespaceRegistry (#1890)

The R-level `ns_registry_env()` is only used in pkgload and I can work
around there. On older R versions it keeps working to facilitate transition.
On newer R versions, it now fails.

The C-level function can call into R. Note that this is also what the
existing `R_FindNamespace()` does
(https://github.com/r-devel/r-svn/blob/c709c242bae2aac5018385d24ab2a6a6c6de3ded/src/main/envir.c#L4232).
I've opted to call `.getNamespace()` which does not load the namespace
if not found (see
https://github.com/r-devel/r-svn/blob/c709c242bae2aac5018385d24ab2a6a6c6de3ded/src/library/base/R/namespace.R#L26-L30).

Author: lionel-

NEWS.md

@@ -1,5 +1,7 @@
 # rlang (development version)
 
+* `ns_registry_env()` is defunct in R >= 4.6.0 for compliance with the C API of R.
+
 * New type-checking functions exported from rlang: `check_bool()`,
   `check_string()`, `check_name()`, `check_number_decimal()`,
   `check_number_whole()`, and `check_data_frame()`. These were

R/env-special.R

@@ -343,15 +343,14 @@ env_label <- function(env) {
 }
 
 #' Return the namespace registry env
-#'
-#' Note that the namespace registry does not behave like a normal
-#' environment because the parent is `NULL` instead of the empty
-#' environment. This is exported for expert usage in development tools
-#' only.
-#'
+#' @description
+#' `r lifecycle::badge("defunct")`
 #' @keywords internal
 #' @export
 ns_registry_env <- function() {
+  if (getRversion() >= "4.6") {
+    deprecate_stop("`ns_registry_env()` is defunct.")
+  }
   .Call(ffi_ns_registry_env)
 }
 

man/ns_registry_env.Rd

@@ -510,7 +510,11 @@ r_obj* ffi_env_bind_list(r_obj* env, r_obj* names, r_obj* data) {
 }
 
 r_obj* ffi_ns_registry_env(void) {
+#if R_VERSION < R_Version(4, 6, 0)
   return R_NamespaceRegistry;
+#else
+  r_abort("`ns_registry_env()` is defunct as of R 4.6.");
+#endif
 }
 
 

src/internal/exported.c

@@ -28,5 +28,8 @@ r_obj* list2env_call;
 static
 r_obj* missing_prim;
 
+static
+r_obj* get_ns_call;
+
 static
 void env_coalesce_plain(r_obj* env, r_obj* from, r_obj* nms);

src/rlang/decl/env-decl.h

@@ -6,12 +6,15 @@ r_obj* rlang_ns_env;
 
 
 r_obj* r_ns_env(const char* pkg) {
-  r_obj* pkg_sym = r_sym(pkg);
-  if (!r_env_has(R_NamespaceRegistry, pkg_sym)) {
+  r_obj* pkg_str = KEEP(r_chr(pkg));
+  r_obj* ns = r_eval_with_x(get_ns_call, pkg_str, r_envs.base);
+  FREE(1);
+
+  if (ns == r_null) {
     r_abort("Can't find namespace `%s`", pkg);
   }
 
-  return r_env_get(R_NamespaceRegistry, pkg_sym);
+  return ns;
 }
 
 r_obj* r_base_ns_get(const char* name) {
@@ -278,6 +281,9 @@ void r_init_library_env(void) {
   r_preserve(remove_call);
 
   r_methods_ns_env = r_parse_eval("asNamespace('methods')", r_envs.base);
+
+  get_ns_call = r_parse(".getNamespace(x)");
+  r_preserve(get_ns_call);
 }
 
 r_obj* rlang_ns_env = NULL;
@@ -308,3 +314,6 @@ r_obj* list2env_call = NULL;
 
 static
 r_obj* missing_prim = NULL;
+
+static
+r_obj* get_ns_call = NULL;