py: Implement default keyword only args.

Should finish addressing issue #524.

py/compile.c

@@ -1035,7 +1035,10 @@ void compile_funcdef_param(compiler_t *comp, mp_parse_node_t pn) {
 
             if (comp->have_star) {
                 comp->num_dict_params += 1;
-#if !MICROPY_EMIT_CPYTHON
+#if MICROPY_EMIT_CPYTHON
+                EMIT_ARG(load_const_str, MP_PARSE_NODE_LEAF_ARG(pn_id), false);
+                compile_node(comp, pn_equal);
+#else
                 // in Micro Python we put the default dict parameters into a dictionary using the bytecode
                 if (comp->num_dict_params == 1) {
                     // in Micro Python we put the default positional parameters into a tuple using the bytecode
@@ -1048,11 +1051,10 @@ void compile_funcdef_param(compiler_t *comp, mp_parse_node_t pn) {
                     // first default dict param, so make the map
                     EMIT_ARG(build_map, 0);
                 }
-#endif
-                EMIT_ARG(load_const_str, MP_PARSE_NODE_LEAF_ARG(pn_id), false);
+
+                // compile value then key, then store it to the dict
                 compile_node(comp, pn_equal);
-#if !MICROPY_EMIT_CPYTHON
-                // in Micro Python we put the default dict parameters into a dictionary using the bytecode
+                EMIT_ARG(load_const_str, MP_PARSE_NODE_LEAF_ARG(pn_id), false);
                 EMIT(store_map);
 #endif
             } else {

py/emitglue.c

@@ -119,14 +119,14 @@ mp_obj_t mp_make_function_from_raw_code(mp_raw_code_t *rc, mp_obj_t def_args, mp
     // def_args must be MP_OBJ_NULL or a tuple
     assert(def_args == MP_OBJ_NULL || MP_OBJ_IS_TYPE(def_args, &mp_type_tuple));
 
-    // TODO implement default kw args
-    assert(def_kw_args == MP_OBJ_NULL);
+    // def_kw_args must be MP_OBJ_NULL or a dict
+    assert(def_kw_args == MP_OBJ_NULL || MP_OBJ_IS_TYPE(def_kw_args, &mp_type_dict));
 
     // make the function, depending on the raw code kind
     mp_obj_t fun;
     switch (rc->kind) {
         case MP_CODE_BYTECODE:
-            fun = mp_obj_new_fun_bc(rc->scope_flags, rc->arg_names, rc->n_pos_args, rc->n_kwonly_args, def_args, rc->u_byte.code);
+            fun = mp_obj_new_fun_bc(rc->scope_flags, rc->arg_names, rc->n_pos_args, rc->n_kwonly_args, def_args, def_kw_args, rc->u_byte.code);
             break;
         case MP_CODE_NATIVE_PY:
             fun = mp_make_function_n(rc->n_pos_args, rc->u_native.fun);

py/obj.h

@@ -380,7 +380,7 @@ mp_obj_t mp_obj_new_exception_arg1(const mp_obj_type_t *exc_type, mp_obj_t arg);
 mp_obj_t mp_obj_new_exception_args(const mp_obj_type_t *exc_type, uint n_args, const mp_obj_t *args);
 mp_obj_t mp_obj_new_exception_msg(const mp_obj_type_t *exc_type, const char *msg);
 mp_obj_t mp_obj_new_exception_msg_varg(const mp_obj_type_t *exc_type, const char *fmt, ...); // counts args by number of % symbols in fmt, excluding %%; can only handle void* sizes (ie no float/double!)
-mp_obj_t mp_obj_new_fun_bc(uint scope_flags, qstr *args, uint n_pos_args, uint n_kwonly_args, mp_obj_t def_args, const byte *code);
+mp_obj_t mp_obj_new_fun_bc(uint scope_flags, qstr *args, uint n_pos_args, uint n_kwonly_args, mp_obj_t def_args, mp_obj_t def_kw_args, const byte *code);
 mp_obj_t mp_obj_new_fun_asm(uint n_args, void *fun);
 mp_obj_t mp_obj_new_gen_wrap(mp_obj_t fun);
 mp_obj_t mp_obj_new_closure(mp_obj_t fun, uint n_closed, const mp_obj_t *closed);

py/objfun.c

@@ -249,6 +249,10 @@ STATIC mp_obj_t fun_bc_call(mp_obj_t self_in, uint n_args, uint n_kw, const mp_o
     // This function is pretty complicated.  It's main aim is to be efficient in speed and RAM
     // usage for the common case of positional only args.
     //
+    // TODO Now that we allocate the state for the bytecode execution, we probably don't
+    // need extra_args anymore, and definitely don't need flat_args.
+    //
+    // TODO The following comment is obsolete and probably wrong:
     // extra_args layout: def_args, var_arg tuple, kwonly args, var_kw dict
 
     DEBUG_printf("Input n_args: %d, n_kw: %d\n", n_args, n_kw);
@@ -260,7 +264,7 @@ STATIC mp_obj_t fun_bc_call(mp_obj_t self_in, uint n_args, uint n_kw, const mp_o
     DEBUG_printf("Func n_def_args: %d\n", self->n_def_args);
 
     const mp_obj_t *kwargs = args + n_args;
-    mp_obj_t *extra_args = self->extra_args + self->n_def_args;
+    mp_obj_t *extra_args = self->extra_args + self->n_def_args + self->has_def_kw_args;
     uint n_extra_args = 0;
 
     // check positional arguments
@@ -295,7 +299,7 @@ STATIC mp_obj_t fun_bc_call(mp_obj_t self_in, uint n_args, uint n_kw, const mp_o
 
     // check keyword arguments
 
-    if (n_kw != 0) {
+    if (n_kw != 0 || self->has_def_kw_args) {
         // We cannot use dynamically-sized array here, because GCC indeed
         // deallocates it on leaving defining scope (unlike most static stack allocs).
         // So, we have 2 choices: allocate it unconditionally at the top of function
@@ -355,10 +359,19 @@ continue2:;
         }
 
         // Check that all mandatory keyword args are specified
+        // Fill in default kw args if we have them
         for (int i = 0; i < self->n_kwonly_args; i++) {
             if (flat_args[self->n_pos_args + i] == MP_OBJ_NULL) {
-                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
-                    "function missing required keyword argument '%s'", qstr_str(self->args[self->n_pos_args + i])));
+                mp_map_elem_t *elem = NULL;
+                if (self->has_def_kw_args) {
+                    elem = mp_map_lookup(&((mp_obj_dict_t*)self->extra_args[self->n_def_args])->map, MP_OBJ_NEW_QSTR(self->args[self->n_pos_args + i]), MP_MAP_LOOKUP);
+                }
+                if (elem != NULL) {
+                    flat_args[self->n_pos_args + i] = elem->value;
+                } else {
+                    nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
+                        "function missing required keyword argument '%s'", qstr_str(self->args[self->n_pos_args + i])));
+                }
             }
         }
 
@@ -513,7 +526,7 @@ const mp_obj_type_t mp_type_fun_bc = {
     .binary_op = fun_binary_op,
 };
 
-mp_obj_t mp_obj_new_fun_bc(uint scope_flags, qstr *args, uint n_pos_args, uint n_kwonly_args, mp_obj_t def_args_in, const byte *code) {
+mp_obj_t mp_obj_new_fun_bc(uint scope_flags, qstr *args, uint n_pos_args, uint n_kwonly_args, mp_obj_t def_args_in, mp_obj_t def_kw_args, const byte *code) {
     uint n_def_args = 0;
     uint n_extra_args = 0;
     mp_obj_tuple_t *def_args = def_args_in;
@@ -522,6 +535,9 @@ mp_obj_t mp_obj_new_fun_bc(uint scope_flags, qstr *args, uint n_pos_args, uint n
         n_def_args = def_args->len;
         n_extra_args = def_args->len;
     }
+    if (def_kw_args != MP_OBJ_NULL) {
+        n_extra_args += 1;
+    }
     if ((scope_flags & MP_SCOPE_FLAG_VARARGS) != 0) {
         n_extra_args += 1;
     }
@@ -535,18 +551,24 @@ mp_obj_t mp_obj_new_fun_bc(uint scope_flags, qstr *args, uint n_pos_args, uint n
     o->n_pos_args = n_pos_args;
     o->n_kwonly_args = n_kwonly_args;
     o->n_def_args = n_def_args;
+    o->has_def_kw_args = def_kw_args != MP_OBJ_NULL;
     o->takes_var_args = (scope_flags & MP_SCOPE_FLAG_VARARGS) != 0;
     o->takes_kw_args = (scope_flags & MP_SCOPE_FLAG_VARKEYWORDS) != 0;
     o->bytecode = code;
-    memset(o->extra_args, 0, n_extra_args * sizeof(mp_obj_t));
+    mp_obj_t *extra_args = o->extra_args;
+    memset(extra_args, 0, n_extra_args * sizeof(mp_obj_t));
     if (def_args != MP_OBJ_NULL) {
-        memcpy(o->extra_args, def_args->items, n_def_args * sizeof(mp_obj_t));
+        memcpy(extra_args, def_args->items, n_def_args * sizeof(mp_obj_t));
+        extra_args += n_def_args;
+    }
+    if (def_kw_args != MP_OBJ_NULL) {
+        *extra_args++ = def_kw_args;
     }
     if ((scope_flags & MP_SCOPE_FLAG_VARARGS) != 0) {
-        o->extra_args[n_def_args] = MP_OBJ_NULL;
+        *extra_args++ = MP_OBJ_NULL;
     }
     if ((scope_flags & MP_SCOPE_FLAG_VARARGS) != 0) {
-        o->extra_args[n_extra_args - 1] = MP_OBJ_NULL;
+        *extra_args = MP_OBJ_NULL;
     }
     return o;
 }

py/objfun.h

@@ -30,10 +30,15 @@ typedef struct _mp_obj_fun_bc_t {
     machine_uint_t n_pos_args : 16;     // number of arguments this function takes
     machine_uint_t n_kwonly_args : 16;  // number of arguments this function takes
     machine_uint_t n_def_args : 16;     // number of default arguments
+    machine_uint_t has_def_kw_args : 1; // set if this function has default keyword args
     machine_uint_t takes_var_args : 1;  // set if this function takes variable args
     machine_uint_t takes_kw_args : 1;   // set if this function takes keyword args
     const byte *bytecode;   // bytecode for the function
     qstr *args;             // argument names (needed to resolve positional args passed as keywords)
-    // values of default args (if any), plus a slot at the end for var args and/or kw args (if it takes them)
+    // the following extra_args array is allocated space to take (in order):
+    //  - values of positional default args (if any)
+    //  - a single slot for default kw args dict (if it has them)
+    //  - a single slot for var args tuple (if it takes them)
+    //  - a single slot for kw args dict (if it takes them)
     mp_obj_t extra_args[];
 } mp_obj_fun_bc_t;

tests/basics/fun-kwonly.py

@@ -43,14 +43,14 @@ def f(a, *, b, **kw):
 f(1, b=2)
 f(1, b=2, c=3)
 
-## with a default value; not currently working
-#def g(a, *, b=2, c):
-#    print(a, b, c)
-#
-#g(1, c=3)
-#g(1, b=3, c=4)
-#g(1, **{'c':3})
-#g(1, **{'b':'3', 'c':4})
+# with a default value
+def g(a, *, b=2, c):
+    print(a, b, c)
+
+g(1, c=3)
+g(1, b=3, c=4)
+g(1, **{'c':3})
+g(1, **{'b':'3', 'c':4})
 
 # with named star
 def f(*a, b, c):