Convert empty keyword hash to required positional argument and warn

In general, we want to ignore empty keyword hashes.  The only case
where we want to allow them for backwards compatibility is when
they are necessary to satify the final required positional argument.
In that case, we want to not ignore them, but we do want to warn,
as that will be going away in Ruby 3.

This commit implements this support for regular methods and
attr_writer methods.

In order to allow send to forward arguments correctly, send no
longer removes empty keyword hashes.  It is the responsibility of
the final method to remove the empty keyword hashes now.  This
change was necessary as otherwise send could remove the empty
keyword hashes before the regular or attr_writer methods could
move them to required positional arguments.

For completeness, add tests for keyword handling regular
methods calls.

This makes rb_warn_keyword_to_last_hash non-static in vm_args.c
so it can be reused in vm_insnhelper.c, and also moves declarations
before statements in the rb_warn_* functions in vm_args.c.

1 files changed, 32 insertions, 14 deletions

diff --git a/vm_args.c b/vm_args.c
index 5f8eb12869..e9a11bd255 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -581,15 +581,16 @@ ignore_keyword_hash_p(VALUE keyword_hash, const rb_iseq_t * const iseq) {
 
 VALUE rb_iseq_location(const rb_iseq_t *iseq);
 
-static inline void
+void
 rb_warn_keyword_to_last_hash(struct rb_calling_info *calling, const struct rb_call_info *ci, const rb_iseq_t * const iseq)
 {
+    VALUE name, loc;
     if (calling->recv == Qundef) {
         rb_warn("The keyword argument is passed as the last hash parameter");
         return;
     }
-    VALUE name = rb_id2str(ci->mid);
-    VALUE loc = rb_iseq_location(iseq);
+    name = rb_id2str(ci->mid);
+    loc = rb_iseq_location(iseq);
     if (NIL_P(loc)) {
         rb_warn("The keyword argument for `%"PRIsVALUE"' is passed as the last hash parameter",
                 name);
@@ -604,9 +605,10 @@ rb_warn_keyword_to_last_hash(struct rb_calling_info *calling, const struct rb_ca
 static inline void
 rb_warn_split_last_hash_to_keyword(struct rb_calling_info *calling, const struct rb_call_info *ci, const rb_iseq_t * const iseq)
 {
+    VALUE name, loc;
     if (calling->recv == Qundef) return;
-    VALUE name = rb_id2str(ci->mid);
-    VALUE loc = rb_iseq_location(iseq);
+    name = rb_id2str(ci->mid);
+    loc = rb_iseq_location(iseq);
     if (NIL_P(loc)) {
         rb_warn("The last argument for `%"PRIsVALUE"' is split into positional and keyword parameters",
                 name);
@@ -621,9 +623,10 @@ rb_warn_split_last_hash_to_keyword(struct rb_calling_info *calling, const struct
 static inline void
 rb_warn_last_hash_to_keyword(struct rb_calling_info *calling, const struct rb_call_info *ci, const rb_iseq_t * const iseq)
 {
+    VALUE name, loc;
     if (calling->recv == Qundef) return;
-    VALUE name = rb_id2str(ci->mid);
-    VALUE loc = rb_iseq_location(iseq);
+    name = rb_id2str(ci->mid);
+    loc = rb_iseq_location(iseq);
     if (NIL_P(loc)) {
         rb_warn("The last argument for `%"PRIsVALUE"' is used as the keyword parameter",
                 name);
@@ -651,6 +654,7 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
     VALUE keyword_hash = Qnil;
     VALUE * const orig_sp = ec->cfp->sp;
     unsigned int i;
+    int remove_empty_keyword_hash = 1;
 
     vm_check_canary(ec, orig_sp);
     /*
@@ -700,6 +704,10 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
 	args->kw_argv = NULL;
     }
 
+    if (given_argc == min_argc) {
+        remove_empty_keyword_hash = 0;
+    }
+
     if (ci->flag & VM_CALL_ARGS_SPLAT) {
 	args->rest = locals[--args->argc];
 	args->rest_index = 0;
@@ -707,19 +715,29 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
         if (kw_flag & VM_CALL_KW_SPLAT) {
             int len = RARRAY_LENINT(args->rest);
             if (len > 0 && ignore_keyword_hash_p(RARRAY_AREF(args->rest, len - 1), iseq)) {
-                arg_rest_dup(args);
-                rb_ary_pop(args->rest);
-                given_argc--;
-                kw_flag &= ~VM_CALL_KW_SPLAT;
+                if (remove_empty_keyword_hash) {
+                    arg_rest_dup(args);
+                    rb_ary_pop(args->rest);
+                    given_argc--;
+                    kw_flag &= ~VM_CALL_KW_SPLAT;
+                }
+                else {
+                    rb_warn_keyword_to_last_hash(calling, ci, iseq);
+                }
 	    }
         }
     }
     else {
         if (kw_flag & VM_CALL_KW_SPLAT) {
             if (ignore_keyword_hash_p(args->argv[args->argc-1], iseq)) {
-                args->argc--;
-                given_argc--;
-                kw_flag &= ~VM_CALL_KW_SPLAT;
+                if (remove_empty_keyword_hash) {
+                    args->argc--;
+                    given_argc--;
+                    kw_flag &= ~VM_CALL_KW_SPLAT;
+                }
+                else {
+                    rb_warn_keyword_to_last_hash(calling, ci, iseq);
+                }
 	    }
         }
 	args->rest = Qfalse;