py: Add builtin help function to core, with default help msg.

This builtin is configured using MICROPY_PY_BUILTINS_HELP, and is disabled
by default.

py/builtin.h

@@ -53,6 +53,7 @@ MP_DECLARE_CONST_FUN_OBJ_3(mp_builtin_setattr_obj);
 MP_DECLARE_CONST_FUN_OBJ_0(mp_builtin_globals_obj);
 MP_DECLARE_CONST_FUN_OBJ_2(mp_builtin_hasattr_obj);
 MP_DECLARE_CONST_FUN_OBJ_1(mp_builtin_hash_obj);
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_help_obj);
 MP_DECLARE_CONST_FUN_OBJ_1(mp_builtin_hex_obj);
 MP_DECLARE_CONST_FUN_OBJ_1(mp_builtin_id_obj);
 MP_DECLARE_CONST_FUN_OBJ_2(mp_builtin_isinstance_obj);
@@ -72,7 +73,6 @@ MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_round_obj);
 MP_DECLARE_CONST_FUN_OBJ_KW(mp_builtin_sorted_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_sum_obj);
 // Defined by a port, but declared here for simplicity
-MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_help_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_input_obj);
 MP_DECLARE_CONST_FUN_OBJ_KW(mp_builtin_open_obj);
 
@@ -118,4 +118,6 @@ extern const mp_obj_module_t mp_module_webrepl;
 extern const mp_obj_module_t mp_module_framebuf;
 extern const mp_obj_module_t mp_module_btree;
 
+extern const char *MICROPY_PY_BUILTINS_HELP_TEXT;
+
 #endif // __MICROPY_INCLUDED_PY_BUILTIN_H__

py/builtinhelp.c

@@ -0,0 +1,98 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2016 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdio.h>
+
+#include "py/builtin.h"
+
+#if MICROPY_PY_BUILTINS_HELP
+
+const char *mp_help_default_text =
+"Welcome to MicroPython!\n"
+"\n"
+"For online docs please visit http://docs.micropython.org/\n"
+"\n"
+"Control commands:\n"
+"  CTRL-A        -- on a blank line, enter raw REPL mode\n"
+"  CTRL-B        -- on a blank line, enter normal REPL mode\n"
+"  CTRL-C        -- interrupt a running program\n"
+"  CTRL-D        -- on a blank line, exit or do a soft reset\n"
+"  CTRL-E        -- on a blank line, enter paste mode\n"
+"\n"
+"For further help on a specific object, type help(obj)\n"
+;
+
+STATIC void mp_help_print_info_about_object(mp_obj_t name_o, mp_obj_t value) {
+    mp_print_str(MP_PYTHON_PRINTER, "  ");
+    mp_obj_print(name_o, PRINT_STR);
+    mp_print_str(MP_PYTHON_PRINTER, " -- ");
+    mp_obj_print(value, PRINT_STR);
+    mp_print_str(MP_PYTHON_PRINTER, "\n");
+}
+
+STATIC void mp_help_print_obj(const mp_obj_t obj) {
+    // try to print something sensible about the given object
+    mp_print_str(MP_PYTHON_PRINTER, "object ");
+    mp_obj_print(obj, PRINT_STR);
+    mp_printf(MP_PYTHON_PRINTER, " is of type %s\n", mp_obj_get_type_str(obj));
+
+    mp_map_t *map = NULL;
+    if (MP_OBJ_IS_TYPE(obj, &mp_type_module)) {
+        map = mp_obj_dict_get_map(mp_obj_module_get_globals(obj));
+    } else {
+        mp_obj_type_t *type;
+        if (MP_OBJ_IS_TYPE(obj, &mp_type_type)) {
+            type = obj;
+        } else {
+            type = mp_obj_get_type(obj);
+        }
+        if (type->locals_dict != MP_OBJ_NULL && MP_OBJ_IS_TYPE(type->locals_dict, &mp_type_dict)) {
+            map = mp_obj_dict_get_map(type->locals_dict);
+        }
+    }
+    if (map != NULL) {
+        for (uint i = 0; i < map->alloc; i++) {
+            if (map->table[i].key != MP_OBJ_NULL) {
+                mp_help_print_info_about_object(map->table[i].key, map->table[i].value);
+            }
+        }
+    }
+}
+
+STATIC mp_obj_t mp_builtin_help(size_t n_args, const mp_obj_t *args) {
+    if (n_args == 0) {
+        // print a general help message
+        mp_print_str(MP_PYTHON_PRINTER, MICROPY_PY_BUILTINS_HELP_TEXT);
+    } else {
+        // try to print something sensible about the given object
+        mp_help_print_obj(args[0]);
+    }
+
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin_help_obj, 0, 1, mp_builtin_help);
+
+#endif // MICROPY_PY_BUILTINS_HELP

py/modbuiltins.c

@@ -666,6 +666,9 @@ STATIC const mp_rom_map_elem_t mp_module_builtins_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_globals), MP_ROM_PTR(&mp_builtin_globals_obj) },
     { MP_ROM_QSTR(MP_QSTR_hasattr), MP_ROM_PTR(&mp_builtin_hasattr_obj) },
     { MP_ROM_QSTR(MP_QSTR_hash), MP_ROM_PTR(&mp_builtin_hash_obj) },
+    #if MICROPY_PY_BUILTINS_HELP
+    { MP_ROM_QSTR(MP_QSTR_help), MP_ROM_PTR(&mp_builtin_help_obj) },
+    #endif
     { MP_ROM_QSTR(MP_QSTR_hex), MP_ROM_PTR(&mp_builtin_hex_obj) },
     { MP_ROM_QSTR(MP_QSTR_id), MP_ROM_PTR(&mp_builtin_id_obj) },
     { MP_ROM_QSTR(MP_QSTR_isinstance), MP_ROM_PTR(&mp_builtin_isinstance_obj) },

py/mpconfig.h

@@ -759,6 +759,17 @@ typedef double mp_float_t;
 #define MICROPY_PY_BUILTINS_MIN_MAX (1)
 #endif
 
+// Whether to provide the help function
+#ifndef MICROPY_PY_BUILTINS_HELP
+#define MICROPY_PY_BUILTINS_HELP (0)
+#endif
+
+// Use this to configure the help text shown for help().  It should be a
+// variable with the type "const char*".  A sensible default is provided.
+#ifndef MICROPY_PY_BUILTINS_HELP_TEXT
+#define MICROPY_PY_BUILTINS_HELP_TEXT mp_help_default_text
+#endif
+
 // Whether to set __file__ for imported modules
 #ifndef MICROPY_PY___FILE__
 #define MICROPY_PY___FILE__ (1)

py/py.mk

@@ -189,6 +189,7 @@ PY_O_BASENAME = \
 	binary.o \
 	builtinimport.o \
 	builtinevex.o \
+	builtinhelp.o \
 	modarray.o \
 	modbuiltins.o \
 	modcollections.o \