mp_obj_t mp_builtin___import__(mp_uint_t n_args, const mp_obj_t *args) {
#if DEBUG_PRINT
    DEBUG_printf("__import__:\n");
    for (mp_uint_t i = 0; i < n_args; i++) {
        DEBUG_printf("  ");
        mp_obj_print(args[i], PRINT_REPR);
        DEBUG_printf("\n");
    }
#endif

    mp_obj_t module_name = args[0];
    mp_obj_t fromtuple = mp_const_none;
    mp_int_t level = 0;
    if (n_args >= 4) {
        fromtuple = args[3];
        if (n_args >= 5) {
            level = MP_OBJ_SMALL_INT_VALUE(args[4]);
        }
    }

    mp_uint_t mod_len;
    const char *mod_str = mp_obj_str_get_data(module_name, &mod_len);

    if (level != 0) {
        // What we want to do here is to take name of current module,
        // chop <level> trailing components, and concatenate with passed-in
        // module name, thus resolving relative import name into absolue.
        // This even appears to be correct per
        // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
        // "Relative imports use a module's __name__ attribute to determine that
        // module's position in the package hierarchy."
        level--;
        mp_obj_t this_name_q = mp_obj_dict_get(mp_globals_get(), MP_OBJ_NEW_QSTR(MP_QSTR___name__));
        assert(this_name_q != MP_OBJ_NULL);
        #if MICROPY_CPYTHON_COMPAT
        if (MP_OBJ_QSTR_VALUE(this_name_q) == MP_QSTR___main__) {
            // This is a module run by -m command-line switch, get its real name from backup attribute
            this_name_q = mp_obj_dict_get(mp_globals_get(), MP_OBJ_NEW_QSTR(MP_QSTR___main__));
        }
        #endif
        mp_map_t *globals_map = mp_obj_dict_get_map(mp_globals_get());
        mp_map_elem_t *elem = mp_map_lookup(globals_map, MP_OBJ_NEW_QSTR(MP_QSTR___path__), MP_MAP_LOOKUP);
        bool is_pkg = (elem != NULL);

#if DEBUG_PRINT
        DEBUG_printf("Current module/package: ");
        mp_obj_print(this_name_q, PRINT_REPR);
        DEBUG_printf(", is_package: %d", is_pkg);
        DEBUG_printf("\n");
#endif

        mp_uint_t this_name_l;
        const char *this_name = mp_obj_str_get_data(this_name_q, &this_name_l);

        const char *p = this_name + this_name_l;
        if (!is_pkg) {
            // We have module, but relative imports are anchored at package, so
            // go there.
            chop_component(this_name, &p);
        }


        uint dots_seen = 0;
        while (level--) {
            chop_component(this_name, &p);
            dots_seen++;
        }

        if (dots_seen == 0 && level >= 1) {
            // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
            // "If the module's name does not contain any package information
            // (e.g. it is set to '__main__') then relative imports are
            // resolved as if the module were a top level module, regardless
            // of where the module is actually located on the file system."
            // Supposedly this if catches this condition and resolve it properly
            // TODO: But nobody knows for sure. This condition happens when
            // package's __init__.py does something like "import .submod". So,
            // maybe we should check for package here? But quote above doesn't
            // talk about packages, it talks about dot-less module names.
            DEBUG_printf("Warning: no dots in current module name and level>0\n");
            p = this_name + this_name_l;
        } else if (level != -1) {
            nlr_raise(mp_obj_new_exception_msg(&mp_type_ImportError, "Invalid relative import"));
        }

        uint new_mod_l = (mod_len == 0 ? (size_t)(p - this_name) : (size_t)(p - this_name) + 1 + mod_len);
        char *new_mod = alloca(new_mod_l);
        memcpy(new_mod, this_name, p - this_name);
        if (mod_len != 0) {
            new_mod[p - this_name] = '.';
            memcpy(new_mod + (p - this_name) + 1, mod_str, mod_len);
        }

        qstr new_mod_q = qstr_from_strn(new_mod, new_mod_l);
        DEBUG_printf("Resolved base name for relative import: '%s'\n", qstr_str(new_mod_q));
        if (new_mod_q == MP_QSTR_) {
            // CPython raises SystemError
            nlr_raise(mp_obj_new_exception_msg(&mp_type_ImportError, "cannot perform relative import"));
        }
        module_name = MP_OBJ_NEW_QSTR(new_mod_q);
        mod_str = new_mod;
        mod_len = new_mod_l;
    }

    // check if module already exists
    qstr module_name_qstr = mp_obj_str_get_qstr(module_name);
    mp_obj_t module_obj = mp_module_get(module_name_qstr);
    if (module_obj != MP_OBJ_NULL) {
        DEBUG_printf("Module already loaded\n");
        // If it's not a package, return module right away
        char *p = strchr(mod_str, '.');
        if (p == NULL) {
            return module_obj;
        }
        // If fromlist is not empty, return leaf module
        if (fromtuple != mp_const_none) {
            return module_obj;
        }
        // Otherwise, we need to return top-level package
        qstr pkg_name = qstr_from_strn(mod_str, p - mod_str);
        return mp_module_get(pkg_name);
    }
    DEBUG_printf("Module not yet loaded\n");

    #if MICROPY_MODULE_FROZEN
    mp_lexer_t *lex = mp_find_frozen_module(mod_str, mod_len);
    if (lex != NULL) {
        module_obj = mp_obj_new_module(module_name_qstr);
        // if args[3] (fromtuple) has magic value False, set up
        // this module for command-line "-m" option (set module's
        // name to __main__ instead of real name).
        // TODO: Duplicated below too.
        if (fromtuple == mp_const_false) {
            mp_obj_module_t *o = module_obj;
            mp_obj_dict_store(o->globals, MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR___main__));
        }
        do_load_from_lexer(module_obj, lex, mod_str);
        return module_obj;
    }
    #endif

    uint last = 0;
    VSTR_FIXED(path, MICROPY_ALLOC_PATH_MAX)
    module_obj = MP_OBJ_NULL;
    mp_obj_t top_module_obj = MP_OBJ_NULL;
    mp_obj_t outer_module_obj = MP_OBJ_NULL;
    uint i;
    for (i = 1; i <= mod_len; i++) {
        if (i == mod_len || mod_str[i] == '.') {
            // create a qstr for the module name up to this depth
            qstr mod_name = qstr_from_strn(mod_str, i);
            DEBUG_printf("Processing module: %s\n", qstr_str(mod_name));
            DEBUG_printf("Previous path: =%.*s=\n", vstr_len(&path), vstr_str(&path));

            // find the file corresponding to the module name
            mp_import_stat_t stat;
            if (vstr_len(&path) == 0) {
                // first module in the dotted-name; search for a directory or file
                stat = find_file(mod_str, i, &path);
            } else {
                // latter module in the dotted-name; append to path
                vstr_add_char(&path, PATH_SEP_CHAR);
                vstr_add_strn(&path, mod_str + last, i - last);
                stat = stat_dir_or_file(&path);
            }
            DEBUG_printf("Current path: %.*s\n", vstr_len(&path), vstr_str(&path));

            if (stat == MP_IMPORT_STAT_NO_EXIST) {
                #if MICROPY_MODULE_WEAK_LINKS
                // check if there is a weak link to this module
                if (i == mod_len) {
                    mp_map_elem_t *el = mp_map_lookup((mp_map_t*)&mp_builtin_module_weak_links_map, MP_OBJ_NEW_QSTR(mod_name), MP_MAP_LOOKUP);
                    if (el == NULL) {
                        goto no_exist;
                    }
                    // found weak linked module
                    module_obj = el->value;
                } else {
                    no_exist:
                #else
                {
                #endif
                    // couldn't find the file, so fail
                    if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
                        nlr_raise(mp_obj_new_exception_msg(&mp_type_ImportError, "module not found"));
                    } else {
                        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ImportError,
                            "no module named '%q'", mod_name));
                    }
                }
            } else {
                // found the file, so get the module
                module_obj = mp_module_get(mod_name);
            }

            if (module_obj == MP_OBJ_NULL) {
                // module not already loaded, so load it!

                module_obj = mp_obj_new_module(mod_name);

                // if args[3] (fromtuple) has magic value False, set up
                // this module for command-line "-m" option (set module's
                // name to __main__ instead of real name).
                if (i == mod_len && fromtuple == mp_const_false) {
                    mp_obj_module_t *o = module_obj;
                    mp_obj_dict_store(o->globals, MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR___main__));
                    #if MICROPY_CPYTHON_COMPAT
                    // Store real name in "__main__" attribute. Choosen semi-randonly, to reuse existing qstr's.
                    mp_obj_dict_store(o->globals, MP_OBJ_NEW_QSTR(MP_QSTR___main__), MP_OBJ_NEW_QSTR(mod_name));
                    #endif
                }

                if (stat == MP_IMPORT_STAT_DIR) {
                    DEBUG_printf("%.*s is dir\n", vstr_len(&path), vstr_str(&path));
                    // https://docs.python.org/3/reference/import.html
                    // "Specifically, any module that contains a __path__ attribute is considered a package."
                    mp_store_attr(module_obj, MP_QSTR___path__, mp_obj_new_str(vstr_str(&path), vstr_len(&path), false));
                    vstr_add_char(&path, PATH_SEP_CHAR);
                    vstr_add_str(&path, "__init__.py");
                    if (mp_import_stat(vstr_null_terminated_str(&path)) != MP_IMPORT_STAT_FILE) {
                        vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                        mp_warning("%s is imported as namespace package", vstr_str(&path));
                    } else {
                        do_load(module_obj, &path);
                        vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                    }
                } else { // MP_IMPORT_STAT_FILE
                    do_load(module_obj, &path);
                    // TODO: We cannot just break here, at the very least, we must execute
                    // trailer code below. But otherwise if there're remaining components,
                    // that would be (??) object path within module, not modules path within FS.
                    // break;
                }
            }
            if (outer_module_obj != MP_OBJ_NULL) {
                qstr s = qstr_from_strn(mod_str + last, i - last);
                mp_store_attr(outer_module_obj, s, module_obj);
            }
            outer_module_obj = module_obj;
            if (top_module_obj == MP_OBJ_NULL) {
                top_module_obj = module_obj;
            }
            last = i + 1;
        }
    }
mp_obj_t mp_builtin___import__(size_t n_args, const mp_obj_t *args) {
#if DEBUG_PRINT
    DEBUG_printf("__import__:\n");
    for (size_t i = 0; i < n_args; i++) {
        DEBUG_printf("  ");
        mp_obj_print(args[i], PRINT_REPR);
        DEBUG_printf("\n");
    }
#endif

    mp_obj_t module_name = args[0];
    mp_obj_t fromtuple = mp_const_none;
    mp_int_t level = 0;
    if (n_args >= 4) {
        fromtuple = args[3];
        if (n_args >= 5) {
            level = MP_OBJ_SMALL_INT_VALUE(args[4]);
            if (level < 0) {
                mp_raise_ValueError(NULL);
            }
        }
    }

    size_t mod_len;
    const char *mod_str = mp_obj_str_get_data(module_name, &mod_len);

    if (level != 0) {
        // What we want to do here is to take name of current module,
        // chop <level> trailing components, and concatenate with passed-in
        // module name, thus resolving relative import name into absolute.
        // This even appears to be correct per
        // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
        // "Relative imports use a module's __name__ attribute to determine that
        // module's position in the package hierarchy."
        level--;
        mp_obj_t this_name_q = mp_obj_dict_get(MP_OBJ_FROM_PTR(mp_globals_get()), MP_OBJ_NEW_QSTR(MP_QSTR___name__));
        assert(this_name_q != MP_OBJ_NULL);
        #if MICROPY_CPYTHON_COMPAT
        if (MP_OBJ_QSTR_VALUE(this_name_q) == MP_QSTR___main__) {
            // This is a module run by -m command-line switch, get its real name from backup attribute
            this_name_q = mp_obj_dict_get(MP_OBJ_FROM_PTR(mp_globals_get()), MP_OBJ_NEW_QSTR(MP_QSTR___main__));
        }
        #endif
        mp_map_t *globals_map = &mp_globals_get()->map;
        mp_map_elem_t *elem = mp_map_lookup(globals_map, MP_OBJ_NEW_QSTR(MP_QSTR___path__), MP_MAP_LOOKUP);
        bool is_pkg = (elem != NULL);

#if DEBUG_PRINT
        DEBUG_printf("Current module/package: ");
        mp_obj_print(this_name_q, PRINT_REPR);
        DEBUG_printf(", is_package: %d", is_pkg);
        DEBUG_printf("\n");
#endif

        size_t this_name_l;
        const char *this_name = mp_obj_str_get_data(this_name_q, &this_name_l);

        const char *p = this_name + this_name_l;
        if (!is_pkg) {
            // We have module, but relative imports are anchored at package, so
            // go there.
            chop_component(this_name, &p);
        }

        while (level--) {
            chop_component(this_name, &p);
        }

        // We must have some component left over to import from
        if (p == this_name) {
            mp_raise_ValueError("cannot perform relative import");
        }

        uint new_mod_l = (mod_len == 0 ? (size_t)(p - this_name) : (size_t)(p - this_name) + 1 + mod_len);
        char *new_mod = mp_local_alloc(new_mod_l);
        memcpy(new_mod, this_name, p - this_name);
        if (mod_len != 0) {
            new_mod[p - this_name] = '.';
            memcpy(new_mod + (p - this_name) + 1, mod_str, mod_len);
        }

        qstr new_mod_q = qstr_from_strn(new_mod, new_mod_l);
        mp_local_free(new_mod);
        DEBUG_printf("Resolved base name for relative import: '%s'\n", qstr_str(new_mod_q));
        module_name = MP_OBJ_NEW_QSTR(new_mod_q);
        mod_str = qstr_str(new_mod_q);
        mod_len = new_mod_l;
    }

    // check if module already exists
    qstr module_name_qstr = mp_obj_str_get_qstr(module_name);
    mp_obj_t module_obj = mp_module_get(module_name_qstr);
    if (module_obj != MP_OBJ_NULL) {
        DEBUG_printf("Module already loaded\n");
        // If it's not a package, return module right away
        char *p = strchr(mod_str, '.');
        if (p == NULL) {
            return module_obj;
        }
        // If fromlist is not empty, return leaf module
        if (fromtuple != mp_const_none) {
            return module_obj;
        }
        // Otherwise, we need to return top-level package
        qstr pkg_name = qstr_from_strn(mod_str, p - mod_str);
        return mp_module_get(pkg_name);
    }
    DEBUG_printf("Module not yet loaded\n");

    uint last = 0;
    VSTR_FIXED(path, MICROPY_ALLOC_PATH_MAX)
    module_obj = MP_OBJ_NULL;
    mp_obj_t top_module_obj = MP_OBJ_NULL;
    mp_obj_t outer_module_obj = MP_OBJ_NULL;
    uint i;
    for (i = 1; i <= mod_len; i++) {
        if (i == mod_len || mod_str[i] == '.') {
            // create a qstr for the module name up to this depth
            qstr mod_name = qstr_from_strn(mod_str, i);
            DEBUG_printf("Processing module: %s\n", qstr_str(mod_name));
            DEBUG_printf("Previous path: =%.*s=\n", vstr_len(&path), vstr_str(&path));

            // find the file corresponding to the module name
            mp_import_stat_t stat;
            if (vstr_len(&path) == 0) {
                // first module in the dotted-name; search for a directory or file
                stat = find_file(mod_str, i, &path);
            } else {
                // latter module in the dotted-name; append to path
                vstr_add_char(&path, PATH_SEP_CHAR);
                vstr_add_strn(&path, mod_str + last, i - last);
                stat = stat_dir_or_file(&path);
            }
            DEBUG_printf("Current path: %.*s\n", vstr_len(&path), vstr_str(&path));

            if (stat == MP_IMPORT_STAT_NO_EXIST) {
                #if MICROPY_MODULE_WEAK_LINKS
                // check if there is a weak link to this module
                if (i == mod_len) {
                    mp_map_elem_t *el = mp_map_lookup((mp_map_t*)&mp_builtin_module_weak_links_map, MP_OBJ_NEW_QSTR(mod_name), MP_MAP_LOOKUP);
                    if (el == NULL) {
                        goto no_exist;
                    }
                    // found weak linked module
                    module_obj = el->value;
                    mp_module_call_init(mod_name, module_obj);
                } else {
                    no_exist:
                #else
                {
                #endif
                    // couldn't find the file, so fail
                    if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
                        mp_raise_msg(&mp_type_ImportError, "module not found");
                    } else {
                        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ImportError,
                            "no module named '%q'", mod_name));
                    }
                }
            } else {
                // found the file, so get the module
                module_obj = mp_module_get(mod_name);
            }

            if (module_obj == MP_OBJ_NULL) {
                // module not already loaded, so load it!

                module_obj = mp_obj_new_module(mod_name);

                // if args[3] (fromtuple) has magic value False, set up
                // this module for command-line "-m" option (set module's
                // name to __main__ instead of real name). Do this only
                // for *modules* however - packages never have their names
                // replaced, instead they're -m'ed using a special __main__
                // submodule in them. (This all apparently is done to not
                // touch package name itself, which is important for future
                // imports).
                if (i == mod_len && fromtuple == mp_const_false && stat != MP_IMPORT_STAT_DIR) {
                    mp_obj_module_t *o = MP_OBJ_TO_PTR(module_obj);
                    mp_obj_dict_store(MP_OBJ_FROM_PTR(o->globals), MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR___main__));
                    #if MICROPY_CPYTHON_COMPAT
                    // Store module as "__main__" in the dictionary of loaded modules (returned by sys.modules).
                    mp_obj_dict_store(MP_OBJ_FROM_PTR(&MP_STATE_VM(mp_loaded_modules_dict)), MP_OBJ_NEW_QSTR(MP_QSTR___main__), module_obj);
                    // Store real name in "__main__" attribute. Chosen semi-randonly, to reuse existing qstr's.
                    mp_obj_dict_store(MP_OBJ_FROM_PTR(o->globals), MP_OBJ_NEW_QSTR(MP_QSTR___main__), MP_OBJ_NEW_QSTR(mod_name));
                    #endif
                }

                if (stat == MP_IMPORT_STAT_DIR) {
                    DEBUG_printf("%.*s is dir\n", vstr_len(&path), vstr_str(&path));
                    // https://docs.python.org/3/reference/import.html
                    // "Specifically, any module that contains a __path__ attribute is considered a package."
                    mp_store_attr(module_obj, MP_QSTR___path__, mp_obj_new_str(vstr_str(&path), vstr_len(&path)));
                    size_t orig_path_len = path.len;
                    vstr_add_char(&path, PATH_SEP_CHAR);
                    vstr_add_str(&path, "__init__.py");
                    if (stat_file_py_or_mpy(&path) != MP_IMPORT_STAT_FILE) {
                        //mp_warning("%s is imported as namespace package", vstr_str(&path));
                    } else {
                        do_load(module_obj, &path);
                    }
                    path.len = orig_path_len;
                } else { // MP_IMPORT_STAT_FILE
                    do_load(module_obj, &path);
                    // This should be the last component in the import path.  If there are
                    // remaining components then it's an ImportError because the current path
                    // (the module that was just loaded) is not a package.  This will be caught
                    // on the next iteration because the file will not exist.
                }
            }
            if (outer_module_obj != MP_OBJ_NULL) {
                qstr s = qstr_from_strn(mod_str + last, i - last);
                mp_store_attr(outer_module_obj, s, module_obj);
            }
            outer_module_obj = module_obj;
            if (top_module_obj == MP_OBJ_NULL) {
                top_module_obj = module_obj;
            }
            last = i + 1;
        }
    }
Exemple #3
0
mp_obj_t mp_builtin___import__(uint n_args, mp_obj_t *args) {
#if DEBUG_PRINT
    printf("__import__:\n");
    for (int i = 0; i < n_args; i++) {
        printf("  ");
        mp_obj_print(args[i], PRINT_REPR);
        printf("\n");
    }
#endif

    mp_obj_t module_name = args[0];
    mp_obj_t fromtuple = mp_const_none;
    int level = 0;
    if (n_args >= 4) {
        fromtuple = args[3];
        if (n_args >= 5) {
            level = MP_OBJ_SMALL_INT_VALUE(args[4]);
        }
    }

    uint mod_len;
    const char *mod_str = (const char*)mp_obj_str_get_data(module_name, &mod_len);

    if (level != 0) {
        // What we want to do here is to take name of current module,
        // chop <level> trailing components, and concatenate with passed-in
        // module name, thus resolving relative import name into absolue.
        // This even appears to be correct per
        // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
        // "Relative imports use a module's __name__ attribute to determine that
        // module's position in the package hierarchy."
        mp_obj_t this_name_q = mp_obj_dict_get(mp_globals_get(), MP_OBJ_NEW_QSTR(MP_QSTR___name__));
        assert(this_name_q != MP_OBJ_NULL);
#if DEBUG_PRINT
        printf("Current module: ");
        mp_obj_print(this_name_q, PRINT_REPR);
        printf("\n");
#endif

        uint this_name_l;
        const char *this_name = (const char*)mp_obj_str_get_data(this_name_q, &this_name_l);

        uint dots_seen = 0;
        const char *p = this_name + this_name_l - 1;
        while (p > this_name) {
            if (*p == '.') {
                dots_seen++;
                if (--level == 0) {
                    break;
                }
            }
            p--;
        }

        if (dots_seen == 0 && level == 1) {
            // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
            // "If the module's name does not contain any package information
            // (e.g. it is set to '__main__') then relative imports are
            // resolved as if the module were a top level module, regardless
            // of where the module is actually located on the file system."
            // Supposedly this if catches this condition and resolve it properly
            // TODO: But nobody knows for sure. This condition happens when
            // package's __init__.py does something like "import .submod". So,
            // maybe we should check for package here? But quote above doesn't
            // talk about packages, it talks about dot-less module names.
            p = this_name + this_name_l;
        } else if (level != 0) {
            nlr_raise(mp_obj_new_exception_msg(&mp_type_ImportError, "Invalid relative import"));
        }

        uint new_mod_l = (mod_len == 0 ? p - this_name : p - this_name + 1 + mod_len);
        char *new_mod = alloca(new_mod_l);
        memcpy(new_mod, this_name, p - this_name);
        if (mod_len != 0) {
            new_mod[p - this_name] = '.';
            memcpy(new_mod + (p - this_name) + 1, mod_str, mod_len);
        }

        qstr new_mod_q = qstr_from_strn(new_mod, new_mod_l);
        DEBUG_printf("Resolved relative name: %s\n", qstr_str(new_mod_q));
        module_name = MP_OBJ_NEW_QSTR(new_mod_q);
        mod_str = new_mod;
        mod_len = new_mod_l;
    }

    // check if module already exists
    mp_obj_t module_obj = mp_module_get(mp_obj_str_get_qstr(module_name));
    if (module_obj != MP_OBJ_NULL) {
        DEBUG_printf("Module already loaded\n");
        // If it's not a package, return module right away
        char *p = strchr(mod_str, '.');
        if (p == NULL) {
            return module_obj;
        }
        // If fromlist is not empty, return leaf module
        if (fromtuple != mp_const_none) {
            return module_obj;
        }
        // Otherwise, we need to return top-level package
        qstr pkg_name = qstr_from_strn(mod_str, p - mod_str);
        return mp_module_get(pkg_name);
    }
    DEBUG_printf("Module not yet loaded\n");

    uint last = 0;
    VSTR_FIXED(path, MICROPY_ALLOC_PATH_MAX)
    module_obj = MP_OBJ_NULL;
    mp_obj_t top_module_obj = MP_OBJ_NULL;
    mp_obj_t outer_module_obj = MP_OBJ_NULL;
    uint i;
    for (i = 1; i <= mod_len; i++) {
        if (i == mod_len || mod_str[i] == '.') {
            // create a qstr for the module name up to this depth
            qstr mod_name = qstr_from_strn(mod_str, i);
            DEBUG_printf("Processing module: %s\n", qstr_str(mod_name));
            DEBUG_printf("Previous path: %s\n", vstr_str(&path));

            // find the file corresponding to the module name
            mp_import_stat_t stat;
            if (vstr_len(&path) == 0) {
                // first module in the dotted-name; search for a directory or file
                stat = find_file(mod_str, i, &path);
            } else {
                // latter module in the dotted-name; append to path
                vstr_add_char(&path, PATH_SEP_CHAR);
                vstr_add_strn(&path, mod_str + last, i - last);
                stat = stat_dir_or_file(&path);
            }
            DEBUG_printf("Current path: %s\n", vstr_str(&path));

            // fail if we couldn't find the file
            if (stat == MP_IMPORT_STAT_NO_EXIST) {
                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ImportError, "No module named '%s'", qstr_str(mod_name)));
            }

            module_obj = mp_module_get(mod_name);
            if (module_obj == MP_OBJ_NULL) {
                // module not already loaded, so load it!

                module_obj = mp_obj_new_module(mod_name);

                if (stat == MP_IMPORT_STAT_DIR) {
                    DEBUG_printf("%s is dir\n", vstr_str(&path));
                    // https://docs.python.org/3/reference/import.html
                    // "Specifically, any module that contains a __path__ attribute is considered a package."
                    mp_store_attr(module_obj, MP_QSTR___path__, mp_obj_new_str(vstr_str(&path), vstr_len(&path), false));
                    vstr_add_char(&path, PATH_SEP_CHAR);
                    vstr_add_str(&path, "__init__.py");
                    if (mp_import_stat(vstr_str(&path)) != MP_IMPORT_STAT_FILE) {
                        vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                        printf("Notice: %s is imported as namespace package\n", vstr_str(&path));
                    } else {
                        do_load(module_obj, &path);
                        vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                    }
                } else { // MP_IMPORT_STAT_FILE
                    do_load(module_obj, &path);
                    // TODO: We cannot just break here, at the very least, we must execute
                    // trailer code below. But otherwise if there're remaining components,
                    // that would be (??) object path within module, not modules path within FS.
                    // break;
                }
            }
            if (outer_module_obj != MP_OBJ_NULL) {
                qstr s = qstr_from_strn(mod_str + last, i - last);
                mp_store_attr(outer_module_obj, s, module_obj);
            }
            outer_module_obj = module_obj;
            if (top_module_obj == MP_OBJ_NULL) {
                top_module_obj = module_obj;
            }
            last = i + 1;
        }
    }

    if (i < mod_len) {
        // we loaded a package, now need to load objects from within that package
        // TODO
        assert(0);
    }

    // If fromlist is not empty, return leaf module
    if (fromtuple != mp_const_none) {
        return module_obj;
    }
    // Otherwise, we need to return top-level package
    return top_module_obj;
}
mp_obj_t mp_builtin___import__(uint n_args, mp_obj_t *args) {
    /*
    printf("import:\n");
    for (int i = 0; i < n_args; i++) {
        printf("  ");
        mp_obj_print(args[i], PRINT_REPR);
        printf("\n");
    }
    */

    mp_obj_t fromtuple = mp_const_none;
    int level = 0;
    if (n_args >= 4) {
        fromtuple = args[3];
        if (n_args >= 5) {
            level = MP_OBJ_SMALL_INT_VALUE(args[4]);
        }
    }

    if (level != 0) {
        nlr_jump(mp_obj_new_exception_msg(&mp_type_NotImplementedError,
            "Relative import is not implemented"));
    }

    uint mod_len;
    const char *mod_str = (const char*)mp_obj_str_get_data(args[0], &mod_len);

    // check if module already exists
    mp_obj_t module_obj = mp_module_get(mp_obj_str_get_qstr(args[0]));
    if (module_obj != MP_OBJ_NULL) {
        // If it's not a package, return module right away
        char *p = strchr(mod_str, '.');
        if (p == NULL) {
            return module_obj;
        }
        // If fromlist is not empty, return leaf module
        if (fromtuple != mp_const_none) {
            return module_obj;
        }
        // Otherwise, we need to return top-level package
        qstr pkg_name = qstr_from_strn(mod_str, p - mod_str);
        return mp_module_get(pkg_name);
    }

    uint last = 0;
    VSTR_FIXED(path, MICROPY_PATH_MAX)
    module_obj = MP_OBJ_NULL;
    mp_obj_t top_module_obj = MP_OBJ_NULL;
    mp_obj_t outer_module_obj = MP_OBJ_NULL;
    uint i;
    for (i = 1; i <= mod_len; i++) {
        if (i == mod_len || mod_str[i] == '.') {
            // create a qstr for the module name up to this depth
            qstr mod_name = qstr_from_strn(mod_str, i);

            // find the file corresponding to the module name
            mp_import_stat_t stat;
            if (vstr_len(&path) == 0) {
                // first module in the dotted-name; search for a directory or file
                stat = find_file(mod_str, i, &path);
            } else {
                // latter module in the dotted-name; append to path
                vstr_add_char(&path, PATH_SEP_CHAR);
                vstr_add_strn(&path, mod_str + last, i - last);
                stat = stat_dir_or_file(&path);
            }

            // fail if we couldn't find the file
            if (stat == MP_IMPORT_STAT_NO_EXIST) {
                nlr_jump(mp_obj_new_exception_msg_varg(&mp_type_ImportError, "ImportError: No module named '%s'", qstr_str(mod_name)));
            }

            module_obj = mp_module_get(mod_name);
            if (module_obj == MP_OBJ_NULL) {
                // module not already loaded, so load it!

                module_obj = mp_obj_new_module(mod_name);

                if (stat == MP_IMPORT_STAT_DIR) {
                    vstr_add_char(&path, PATH_SEP_CHAR);
                    vstr_add_str(&path, "__init__.py");
                    if (mp_import_stat(vstr_str(&path)) != MP_IMPORT_STAT_FILE) {
                        vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                        nlr_jump(mp_obj_new_exception_msg_varg(&mp_type_ImportError,
                            "Per PEP-420 a dir without __init__.py (%s) is a namespace package; "
                            "namespace packages are not supported", vstr_str(&path)));
                    }
                    do_load(module_obj, &path);
                    vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                } else { // MP_IMPORT_STAT_FILE
                    do_load(module_obj, &path);
                    // TODO: We cannot just break here, at the very least, we must execute
                    // trailer code below. But otherwise if there're remaining components,
                    // that would be (??) object path within module, not modules path within FS.
                    // break;
                }
            }
            if (outer_module_obj != MP_OBJ_NULL) {
                qstr s = qstr_from_strn(mod_str + last, i - last);
                mp_store_attr(outer_module_obj, s, module_obj);
            }
            outer_module_obj = module_obj;
            if (top_module_obj == MP_OBJ_NULL) {
                top_module_obj = module_obj;
            }
            last = i + 1;
        }
    }

    if (i < mod_len) {
        // we loaded a package, now need to load objects from within that package
        // TODO
        assert(0);
    }

    // If fromlist is not empty, return leaf module
    if (fromtuple != mp_const_none) {
        return module_obj;
    }
    // Otherwise, we need to return top-level package
    return top_module_obj;
}