objstr: Implement kwargs support for str.format().

py/modbuiltins.c

@@ -141,7 +141,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_any_obj, mp_builtin_any);
 
 STATIC mp_obj_t mp_builtin_bin(mp_obj_t o_in) {
     mp_obj_t args[] = { MP_OBJ_NEW_QSTR(MP_QSTR__brace_open__colon__hash_b_brace_close_), o_in };
-    return mp_obj_str_format(MP_ARRAY_SIZE(args), args);
+    return mp_obj_str_format(MP_ARRAY_SIZE(args), args, MP_OBJ_NULL);
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_bin_obj, mp_builtin_bin);
 

py/objstr.c

@@ -832,7 +832,7 @@ STATIC NORETURN void terse_str_format_value_error(void) {
     nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "bad format string"));
 }
 
-mp_obj_t mp_obj_str_format(mp_uint_t n_args, const mp_obj_t *args) {
+mp_obj_t mp_obj_str_format(mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
     assert(MP_OBJ_IS_STR_OR_BYTES(args[0]));
 
     GET_STR_DATA_LEN(args[0], str, len);
@@ -932,6 +932,10 @@ mp_obj_t mp_obj_str_format(mp_uint_t n_args, const mp_obj_t *args) {
         mp_obj_t arg = mp_const_none;
 
         if (field_name) {
+            int index = 0;
+            const char *field = vstr_str(field_name);
+            const char *lookup = NULL;
+            if (MP_LIKELY(unichar_isdigit(*field))) {
                 if (arg_i > 0) {
                     if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
                         terse_str_format_value_error();
@@ -940,15 +944,24 @@ mp_obj_t mp_obj_str_format(mp_uint_t n_args, const mp_obj_t *args) {
                             "can't switch from automatic field numbering to manual field specification"));
                     }
                 }
-            int index = 0;
-            if (str_to_int(vstr_str(field_name), &index) != vstr_len(field_name) - 1) {
-                nlr_raise(mp_obj_new_exception_msg(&mp_type_KeyError, "attributes not supported yet"));
-            }
+                lookup = str_to_int(vstr_str(field_name), &index) + field;
                 if (index >= n_args - 1) {
                     nlr_raise(mp_obj_new_exception_msg(&mp_type_IndexError, "tuple index out of range"));
                 }
                 arg = args[index + 1];
                 arg_i = -1;
+            } else {
+                for (lookup = field; *lookup && *lookup != '.' && *lookup != '['; lookup++);
+                mp_obj_t field_q = mp_obj_new_str(field, lookup - field, true/*?*/);
+                mp_map_elem_t *key_elem = mp_map_lookup(kwargs, field_q, MP_MAP_LOOKUP);
+                if (key_elem == NULL) {
+                    nlr_raise(mp_obj_new_exception_arg1(&mp_type_KeyError, field_q));
+                }
+                arg = key_elem->value;
+            }
+            if (*lookup) {
+                nlr_raise(mp_obj_new_exception_msg(&mp_type_NotImplementedError, "attributes not supported yet"));
+            }
             vstr_free(field_name);
             field_name = NULL;
         } else {
@@ -1775,7 +1788,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_endswith_obj, 2, 3, str_endswith);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_strip_obj, 1, 2, str_strip);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_lstrip_obj, 1, 2, str_lstrip);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rstrip_obj, 1, 2, str_rstrip);
-MP_DEFINE_CONST_FUN_OBJ_VAR(str_format_obj, 1, mp_obj_str_format);
+MP_DEFINE_CONST_FUN_OBJ_KW(str_format_obj, 1, mp_obj_str_format);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_replace_obj, 3, 4, str_replace);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_count_obj, 2, 4, str_count);
 MP_DEFINE_CONST_FUN_OBJ_2(str_partition_obj, str_partition);

py/objstr.h

@@ -55,7 +55,7 @@ typedef struct _mp_obj_str_t {
     else { str_len = ((mp_obj_str_t*)str_obj_in)->len; str_data = ((mp_obj_str_t*)str_obj_in)->data; }
 
 void mp_str_print_json(void (*print)(void *env, const char *fmt, ...), void *env, const byte *str_data, mp_uint_t str_len);
-mp_obj_t mp_obj_str_format(mp_uint_t n_args, const mp_obj_t *args);
+mp_obj_t mp_obj_str_format(mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kwargs);
 mp_obj_t mp_obj_new_str_of_type(const mp_obj_type_t *type, const byte* data, mp_uint_t len);
 
 mp_obj_t mp_obj_str_binary_op(mp_uint_t op, mp_obj_t lhs_in, mp_obj_t rhs_in);

tests/basics/string_format.py

@@ -60,6 +60,10 @@ test("{:@<6d}",  -123)
 test("{:@=6d}",  -123)
 test("{:06d}",  -123)
 
+print("{foo}/foo".format(foo="bar"))
+print("{}".format(123, foo="bar"))
+print("{}-{foo}".format(123, foo="bar"))
+
 def test_fmt(conv, fill, alignment, sign, prefix, width, precision, type, arg):
     fmt = '{'
     if conv: