py: Add keyword arg support to enumerate constructor.

Need to have a policy as to how far we go adding keyword support to
built ins.  It's nice to have, and gets better CPython compatibility,
but hurts the micro nature of uPy.

Addresses issue #577.

py/argcheck.c

@@ -103,3 +103,9 @@ void mp_arg_parse_all(uint n_pos, const mp_obj_t *pos, mp_map_t *kws, uint n_all
         nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "extra keyword arguments given"));
     }
 }
+
+void mp_arg_parse_all_kw_array(uint n_pos, uint n_kw, const mp_obj_t *args, uint n_allowed, const mp_arg_t *allowed, mp_arg_val_t *out_vals) {
+    mp_map_t kw_args;
+    mp_map_init_fixed_table(&kw_args, n_kw, args + n_pos);
+    mp_arg_parse_all(n_pos, args, &kw_args, n_allowed, allowed, out_vals);
+}

py/objenumerate.c

@@ -41,14 +41,23 @@ typedef struct _mp_obj_enumerate_t {
 
 STATIC mp_obj_t enumerate_iternext(mp_obj_t self_in);
 
-/* TODO: enumerate is one of the ones that can take args or kwargs.
-   Sticking to args for now */
+STATIC const mp_arg_t enumerate_make_new_args[] = {
+    { MP_QSTR_iterable, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+    { MP_QSTR_start, MP_ARG_INT, {.u_int = 0} },
+};
+#define ENUMERATE_MAKE_NEW_NUM_ARGS ARRAY_SIZE(enumerate_make_new_args)
+
 STATIC mp_obj_t enumerate_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
-    assert(n_args > 0);
+    // parse args
+    mp_arg_val_t vals[ENUMERATE_MAKE_NEW_NUM_ARGS];
+    mp_arg_parse_all_kw_array(n_args, n_kw, args, ENUMERATE_MAKE_NEW_NUM_ARGS, enumerate_make_new_args, vals);
+
+    // create enumerate object
     mp_obj_enumerate_t *o = m_new_obj(mp_obj_enumerate_t);
     o->base.type = &mp_type_enumerate;
-    o->iter = mp_getiter(args[0]);
-    o->cur = n_args > 1 ? mp_obj_get_int(args[1]) : 0;
+    o->iter = mp_getiter(vals[0].u_obj);
+    o->cur = vals[1].u_int;
+
     return o;
 }
 

py/qstrdefs.h

@@ -238,6 +238,8 @@ Q(startswith)
 Q(replace)
 Q(partition)
 Q(rpartition)
+Q(iterable)
+Q(start)
 
 Q(bound_method)
 Q(closure)

py/runtime.h

@@ -56,6 +56,7 @@ void mp_deinit(void);
 
 void mp_arg_check_num(uint n_args, uint n_kw, uint n_args_min, uint n_args_max, bool takes_kw);
 void mp_arg_parse_all(uint n_pos, const mp_obj_t *pos, mp_map_t *kws, uint n_allowed, const mp_arg_t *allowed, mp_arg_val_t *out_vals);
+void mp_arg_parse_all_kw_array(uint n_pos, uint n_kw, const mp_obj_t *args, uint n_allowed, const mp_arg_t *allowed, mp_arg_val_t *out_vals);
 
 mp_obj_dict_t *mp_locals_get(void);
 void mp_locals_set(mp_obj_dict_t *d);

stmhal/extint.c

@@ -302,10 +302,8 @@ STATIC mp_obj_t extint_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
     // type_in == extint_obj_type
 
     // parse args
-    mp_map_t kw_args;
-    mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
     mp_arg_val_t vals[PYB_EXTINT_MAKE_NEW_NUM_ARGS];
-    mp_arg_parse_all(n_args, args, &kw_args, PYB_EXTINT_MAKE_NEW_NUM_ARGS, pyb_extint_make_new_args, vals);
+    mp_arg_parse_all_kw_array(n_args, n_kw, args, PYB_EXTINT_MAKE_NEW_NUM_ARGS, pyb_extint_make_new_args, vals);
 
     extint_obj_t *self = m_new_obj(extint_obj_t);
     self->base.type = type_in;

tests/basics/enumerate.py

@@ -4,3 +4,7 @@ print(list(enumerate([1, 2, 3], 5)))
 print(list(enumerate([1, 2, 3], -5)))
 print(list(enumerate(range(1000))))
 
+# specifying args with keywords
+print(list(enumerate([1, 2, 3], start=1)))
+print(list(enumerate(iterable=[1, 2, 3])))
+print(list(enumerate(iterable=[1, 2, 3], start=1)))