Support Ruby3.0 keyword arguments.

The Difference

Since Ruby1.9, the keyword arguments were emulated by Ruby using the hash
object at the bottom of the arguments. But we have gradually moved toward
keyword arguments separated from normal (positinal) arguments.

At the same time, we value compatibility, so that Ruby3.0 keyword
arguments are somewhat compromise. Basically, keyword arguments are
separated from positional arguments, except when the method does not
take any formal keyword arguments, given keyword arguments (packed
in the hash object) are considered as the last argument.

And we also allow non symbol keys in the keyword arguments. In that
case, those keys are just passed in the `**` hash (or raise
`ArgumentError` for unknown keys).

The Instruction Changes

We have changed `OP_SEND` instruction. `OP_SEND` instruction used to
take 3 operands, the register, the symbol, the number of (positional)
arguments. The meaning of the third operand has been changed. It is now
considered as `n|(nk<<4)`, where `n` is the number of positional
arguments, and `nk` is the number of keyword arguments, both occupies
4 bits in the operand.

The number `15` in both `n` and `nk` means variable sized arguments are
packed in the object. Positional arguments will be packed in the array,
and keyword arguments will be packed in the hash object. That means
arguments more than 14 values are always packed in the object.

Arguments information for other instructions (`OP_SENDB` and `OP_SUPER`)
are also changed. It works as the third operand of `OP_SEND`. the
difference between `OP_SEND` and `OP_SENDB` is just trivial. It assigns
`nil` to the block hidden arguments (right after arguments).

The instruction `OP_SENDV` and `OP_SENDVB` are removed. Those
instructions are replaced by `OP_SEND` and `OP_SENDB` respectively with
the `15` (variable sized) argument information.

Calling Convention

When calling a method, the stack elements shall be in the order of the
receiver of the method, positional arguments, keyword arguments and the
block argument. If the number of positional or keyword arugument (`n` or
`nk`) is zero, corresponding arguments will be empty. So when `n=0` and
`nk=0` the stack layout (from bottom to top) will be:

+-----------------------+
| recv | block (or nil) |
+-----------------------+

The last elements `block` should be explicitly filled before `OP_SEND`
or assigned to `nil` by `OP_SENDB` internally. In other words, the
following have exactly same behavior:

OP_SENDB clears `block` implicitly:

```
OP_SENDB reg sym 0
```

OP_SEND clears `block` implicitly:

```
OP_LOADNIL  R2
OP_SEND     R2 sym 0
```

When calling a method with only positional arguments (n=0..14) without
keyword arguments, the stack layout will be like following:

+--------------------------------------------+
| recv | arg1 | ... | arg_n | block (or nil) |
+--------------------------------------------+

When calling a method with arguments packed in the array (n=15) which
means argument splat (*) is used in the actual arguments, or more than
14 arguments are passed the stack layout will be like following:

+-------------------------------+
| recv | array | block (or nil) |
+-------------------------------+

The number of the actual arguments is determined by the length of the
argument array.

When keyword arguments are given (nk>0), keyword arguments are passed
between positional arguments and the block argument. For example, when
we pass one positional argument `1` and one keyword argument `a: 2`,
the stack layout will be like:

+------------------------------------+
| recv | 1 | :a | 2 | block (or nil) |
+------------------------------------+

Note that keyword arguments consume `2*nk` elements in the stack when
`nk=0..14` (unpacked).

When calling a method with keyword arguments packed in the hash object
(nk=15) which means keyword argument splat (**) is used or more than
14 keyword arguments in the actual arguments, the stack layout will
be like:

+------------------------------+
| recv | hash | block (or nil) |
+------------------------------+

Note for mruby/c

When mruby/c authors try to support new keyword arguments, they need
to handle the new meaning of the argument information operand. If they
choose not to support keyword arguments in mruby/c, it just raise
error when `nk` (taken by `(c>>4)&0xf`) is not zero. And combine
`OP_SENDV` behavior with `OP_SEND` when `n` is `15`.

If they want to support keyword arguments seriously, contact me at
<[email protected]> or `@yukihiro_matz`. I can help you.

1 files changed, 67 insertions, 42 deletions

diff --git a/src/class.c b/src/class.c
index fdf63794b..1403ed48e 100644
--- a/src/class.c
+++ b/src/class.c
@@ -812,9 +812,9 @@ ensure_class_type(mrb_state *mrb, mrb_value val)
 MRB_API mrb_int
 mrb_get_argc(mrb_state *mrb)
 {
-  mrb_int argc = mrb->c->ci->argc;
+  mrb_int argc = mrb->c->ci->n;
 
-  if (argc < 0) {
+  if (argc == 15) {
     struct RArray *a = mrb_ary_ptr(mrb->c->ci->stack[1]);
 
     argc = ARY_LEN(a);
@@ -825,9 +825,9 @@ mrb_get_argc(mrb_state *mrb)
 MRB_API const mrb_value*
 mrb_get_argv(mrb_state *mrb)
 {
-  mrb_int argc = mrb->c->ci->argc;
+  mrb_int argc = mrb->c->ci->n;
   mrb_value *array_argv = mrb->c->ci->stack + 1;
-  if (argc < 0) {
+  if (argc == 15) {
     struct RArray *a = mrb_ary_ptr(*array_argv);
 
     array_argv = ARY_PTR(a);
@@ -838,33 +838,37 @@ mrb_get_argv(mrb_state *mrb)
 MRB_API mrb_value
 mrb_get_arg1(mrb_state *mrb)
 {
-  mrb_int argc = mrb->c->ci->argc;
-  mrb_value *array_argv = mrb->c->ci->stack + 1;
-  if (argc < 0) {
+  mrb_callinfo *ci = mrb->c->ci;
+  mrb_int argc = ci->n;
+  mrb_value *array_argv = ci->stack + 1;
+  if (argc == 15) {
     struct RArray *a = mrb_ary_ptr(*array_argv);
 
     argc = ARY_LEN(a);
     array_argv = ARY_PTR(a);
   }
+  if (argc == 0 && ci->nk == 15) {
+    mrb_int n = ci->n;
+    if (n == 15) n = 1;
+    return ci->stack[n+1];      /* kwhash next to positional arguments */
+  }
   if (argc != 1) {
     mrb_argnum_error(mrb, argc, 1, 1);
   }
   return array_argv[0];
 }
 
+mrb_int mrb_ci_bidx(mrb_callinfo *ci);
+
 MRB_API mrb_bool
 mrb_block_given_p(mrb_state *mrb)
 {
-  const mrb_callinfo *ci = mrb->c->ci;
-  int argc = ci->argc;
-  int idx = (argc < 0) ? 2 : argc + 1;
-  mrb_value b = ci->stack[idx];
+  mrb_callinfo *ci = mrb->c->ci;
+  mrb_value b = ci->stack[mrb_ci_bidx(ci)];
 
   return !mrb_nil_p(b);
 }
 
-void mrb_hash_check_kdict(mrb_state *mrb, mrb_value self);
-
 /*
   retrieve arguments from mrb_state.
 
@@ -911,21 +915,17 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
   char c;
   int i = 0;
   va_list ap;
-  int argc = mrb->c->ci->argc;
-  const mrb_value *argv = mrb->c->ci->stack+1;
-  mrb_bool argv_on_stack = argc >= 0;
+  mrb_callinfo *ci = mrb->c->ci;
+  int argc = ci->n;
+  const mrb_value *argv = ci->stack+1;
+  mrb_bool argv_on_stack;
   mrb_bool opt = FALSE;
   mrb_bool opt_skip = TRUE;
   const mrb_value *pickarg = NULL; /* arguments currently being processed */
-  mrb_value kdict;
+  mrb_value kdict = mrb_nil_value();
   mrb_bool reqkarg = FALSE;
   int argc_min = 0, argc_max = 0;
 
-  if (!argv_on_stack) {
-    struct RArray *a = mrb_ary_ptr(*argv);
-    argv = ARY_PTR(a);
-    argc = ARY_LEN(a);
-  }
   va_start(ap, format);
 
   while ((c = *fmt++)) {
@@ -955,12 +955,41 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
   }
 
  check_exit:
-  if (reqkarg && argc > argc_min && mrb_hash_p(kdict = argv[argc - 1])) {
-    mrb_hash_check_kdict(mrb, kdict);
-    argc--;
+  if (!reqkarg && ci->nk > 0) {
+    mrb_assert(ci->nk == 15);
+    kdict = ci->stack[mrb_ci_bidx(ci)-1];
+    if (mrb_hash_p(kdict) && mrb_hash_size(mrb, kdict) > 0) {
+      if (argc < 14) {
+        ci->n++;
+        argc++;    /* include kdict in normal arguments */
+      }
+      else {
+        /* 14+1 == 15 so pack first */
+        if (argc == 14) {
+          /* pack arguments and kdict */
+          ci->stack[1] = mrb_ary_new_from_values(mrb, argc+1, &ci->stack[1]);
+          argc = ci->n = 15;
+        }
+        else {
+          /* push kdict to packed arguments */
+          mrb_ary_push(mrb, ci->stack[1], kdict);
+        }
+        ci->stack[2] = ci->stack[mrb_ci_bidx(ci)];
+      }
+      ci->nk = 0;
+    }
   }
-  else {
-    kdict = mrb_nil_value();
+  if (reqkarg && ci->nk > 0) {
+    kdict = ci->stack[mrb_ci_bidx(ci)-1];
+    mrb_assert(ci->nk == 15);
+    mrb_assert(mrb_hash_p(kdict));
+  }
+
+  argv_on_stack = argc < 15;
+  if (!argv_on_stack) {
+    struct RArray *a = mrb_ary_ptr(*argv);
+    argv = ARY_PTR(a);
+    argc = ARY_LEN(a);
   }
 
   opt = FALSE;
@@ -989,7 +1018,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
     case '|': case '*': case '&': case '?': case ':':
       if (needmodify) {
       bad_needmodify:
-        mrb_raisef(mrb, E_ARGUMENT_ERROR, "wrong `%c+` modified specifer`", c);
+        mrb_raisef(mrb, E_ARGUMENT_ERROR, "wrong `%c+` modified specifier`", c);
       }
       break;
     default:
@@ -1200,12 +1229,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
         mrb_value *p, *bp;
 
         p = va_arg(ap, mrb_value*);
-        if (mrb->c->ci->argc < 0) {
-          bp = mrb->c->ci->stack + 2;
-        }
-        else {
-          bp = mrb->c->ci->stack + mrb->c->ci->argc + 1;
-        }
+        bp = ci->stack + mrb_ci_bidx(ci);
         if (altmode && mrb_nil_p(*bp)) {
           mrb_raise(mrb, E_ARGUMENT_ERROR, "no block given");
         }
@@ -2812,14 +2836,15 @@ inspect_main(mrb_state *mrb, mrb_value mod)
 }
 
 static const mrb_code new_iseq[] = {
-  OP_ENTER, 0x0, 0x10, 0x1,  /* OP_ENTER     0:0:1:0:0:0:1 */
-  OP_LOADSELF, 0x3,          /* OP_LOADSELF  R3 */
-  OP_SEND, 0x3, 0x0, 0x0,    /* OP_SEND      R3  :allocate  0 */
-  OP_MOVE, 0x0, 0x3,         /* OP_MOVE      R0  R3 */
-  OP_MOVE, 0x4, 0x1,         /* OP_MOVE      R4  R1 */
-  OP_MOVE, 0x5, 0x2,         /* OP_MOVE      R5  R2 */
-  OP_SENDVB, 0x3, 0x1,       /* OP_SENDVB    R3  :initialize */
-  OP_RETURN, 0x0             /* OP_RETURN    R0 */
+  OP_ENTER, 0x0, 0x10, 0x3,  // OP_ENTER     0:0:1:0:0:1:1
+  OP_LOADSELF, 4,            // OP_LOADSELF  R4
+  OP_SEND, 4, 0, 0,          // OP_SEND      R4  :allocate  n=0
+  OP_MOVE, 0, 4,             // OP_MOVE      R0  R4
+  OP_MOVE, 5, 1,             // OP_MOVE      R5  R1 (*)
+  OP_MOVE, 6, 2,             // OP_MOVE      R6  R2 (**)
+  OP_MOVE, 7, 3,             // OP_MOVE      R7  R3
+  OP_SENDB, 4, 1, 255,       // OP_SENDB     R4  :initialize n=*|nk=*
+  OP_RETURN, 0               // OP_RETURN    R0
 };
 
 MRB_PRESYM_DEFINE_VAR_AND_INITER(new_syms, 2, MRB_SYM(allocate), MRB_SYM(initialize))