py/builtinimport: Remove partially-loaded modules from sys.modules.

Prior to this commit, importing a module that exists but has a syntax error
or some other problem that happens at import time would result in a
potentially-incomplete module object getting added to sys.modules.
Subsequent imports would use that object, resulting in confusing error
messages that hide the root cause of the problem.

This commit fixes that issue by removing the failed module from sys.modules
using the new NLR callback mechanism.

Note that it is still important to add the module to sys.modules while the
import is happening so that we can support circular imports just like
CPython does.

Fixes issue #967.

Signed-off-by: David Grayson <davidegrayson@gmail.com>
This commit is contained in:
David Grayson 2023-06-04 19:55:41 -07:00 committed by Damien George
parent ce31e5a2dc
commit a79a6ab364
8 changed files with 62 additions and 19 deletions

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@ -346,6 +346,17 @@ STATIC void evaluate_relative_import(mp_int_t level, const char **module_name, s
*module_name_len = new_module_name_len; *module_name_len = new_module_name_len;
} }
typedef struct _nlr_jump_callback_node_unregister_module_t {
nlr_jump_callback_node_t callback;
qstr name;
} nlr_jump_callback_node_unregister_module_t;
STATIC void unregister_module_from_nlr_jump_callback(void *ctx_in) {
nlr_jump_callback_node_unregister_module_t *ctx = ctx_in;
mp_map_t *mp_loaded_modules_map = &MP_STATE_VM(mp_loaded_modules_dict).map;
mp_map_lookup(mp_loaded_modules_map, MP_OBJ_NEW_QSTR(ctx->name), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
}
// Load a module at the specified absolute path, possibly as a submodule of the given outer module. // Load a module at the specified absolute path, possibly as a submodule of the given outer module.
// full_mod_name: The full absolute path up to this level (e.g. "foo.bar.baz"). // full_mod_name: The full absolute path up to this level (e.g. "foo.bar.baz").
// level_mod_name: The final component of the path (e.g. "baz"). // level_mod_name: The final component of the path (e.g. "baz").
@ -467,8 +478,13 @@ STATIC mp_obj_t process_import_at_level(qstr full_mod_name, qstr level_mod_name,
// Module was found on the filesystem/frozen, try and load it. // Module was found on the filesystem/frozen, try and load it.
DEBUG_printf("Found path to load: %.*s\n", (int)vstr_len(&path), vstr_str(&path)); DEBUG_printf("Found path to load: %.*s\n", (int)vstr_len(&path), vstr_str(&path));
// Prepare for loading from the filesystem. Create a new shell module. // Prepare for loading from the filesystem. Create a new shell module
// and register it in sys.modules. Also make sure we remove it if
// there is any problem below.
module_obj = mp_obj_new_module(full_mod_name); module_obj = mp_obj_new_module(full_mod_name);
nlr_jump_callback_node_unregister_module_t ctx;
ctx.name = full_mod_name;
nlr_push_jump_callback(&ctx.callback, unregister_module_from_nlr_jump_callback);
#if MICROPY_MODULE_OVERRIDE_MAIN_IMPORT #if MICROPY_MODULE_OVERRIDE_MAIN_IMPORT
// If this module is being loaded via -m on unix, then // If this module is being loaded via -m on unix, then
@ -526,6 +542,8 @@ STATIC mp_obj_t process_import_at_level(qstr full_mod_name, qstr level_mod_name,
mp_store_attr(outer_module_obj, level_mod_name, module_obj); mp_store_attr(outer_module_obj, level_mod_name, module_obj);
} }
nlr_pop_jump_callback(false);
return module_obj; return module_obj;
} }

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@ -1,18 +0,0 @@
"""
categories: Core,import
description: Failed to load modules are still registered as loaded
cause: To make module handling more efficient, it's not wrapped with exception handling.
workaround: Test modules before production use; during development, use ``del sys.modules["name"]``, or just soft or hard reset the board.
"""
import sys
try:
from modules import foo
except NameError as e:
print(e)
try:
from modules import foo
print("Should not get here")
except NameError as e:
print(e)

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@ -0,0 +1,2 @@
import pkg2
import broken.zerodiv

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@ -0,0 +1 @@
1 / 0

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@ -0,0 +1,4 @@
x = 1
import circular.sub
print(circular.sub.y)

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@ -0,0 +1,3 @@
from circular.main import x
y = x + 20

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@ -0,0 +1,32 @@
import sys, pkg
# Modules we import are usually added to sys.modules.
print("pkg" in sys.modules)
try:
from broken.zerodiv import x
except Exception as e:
print(e.__class__.__name__)
# The broken module we tried to import should not be in sys.modules.
print("broken.zerodiv" in sys.modules)
# If we try to import the module again, the code should
# run again and we should get the same error.
try:
from broken.zerodiv import x
except Exception as e:
print(e.__class__.__name__)
# Import a module that successfully imports some other modules
# before importing the problematic module.
try:
import broken.pkg2_and_zerodiv
except ZeroDivisionError:
pass
print("pkg2" in sys.modules)
print("pkg2.mod1" in sys.modules)
print("pkg2.mod2" in sys.modules)
print("broken.zerodiv" in sys.modules)
print("broken.pkg2_and_zerodiv" in sys.modules)

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@ -0,0 +1 @@
import circular.main