py: Automatically provide weak links from "foo" to "ufoo" module name.

This commit implements automatic module weak links for all built-in
modules, by searching for "ufoo" in the built-in module list if "foo"
cannot be found.  This means that all modules named "ufoo" are always
available as "foo".  Also, a port can no longer add any other weak links,
which makes strict the definition of a weak link.

It saves some code size (about 100-200 bytes) on ports that previously had
lots of weak links.

Some changes from the previous behaviour:
- It doesn't intern the non-u module names (eg "foo" is not interned),
  which saves code size, but will mean that "import foo" creates a new qstr
  (namely "foo") in RAM (unless the importing module is frozen).
- help('modules') no longer lists non-u module names, only the u-variants;
  this reduces duplication in the help listing.

Weak links are effectively the same as having a set of symbolic links on
the filesystem that is searched last.  So an "import foo" will search
built-in modules first, then all paths in sys.path, then weak links last,
importing "ufoo" if it exists.  Thus a file called "foo.py" somewhere in
sys.path will still have precedence over the weak link of "foo" to "ufoo".

See issues: #1740, #4449, #5229, #5241.

7 files changed, 0 insertions, 101 deletions

diff --git a/ports/cc3200/mpconfigport.h b/ports/cc3200/mpconfigport.h
index e7894dd02..d5c3c07e4 100644
--- a/ports/cc3200/mpconfigport.h
+++ b/ports/cc3200/mpconfigport.h
@@ -169,19 +169,6 @@ extern const struct _mp_obj_module_t mp_module_ussl;
     { MP_ROM_QSTR(MP_QSTR_ubinascii),   MP_ROM_PTR(&mp_module_ubinascii) }, \
     { MP_ROM_QSTR(MP_QSTR_ussl),        MP_ROM_PTR(&mp_module_ussl) },      \
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_errno),       MP_ROM_PTR(&mp_module_uerrno) },    \
-    { MP_ROM_QSTR(MP_QSTR_struct),      MP_ROM_PTR(&mp_module_ustruct) },   \
-    { MP_ROM_QSTR(MP_QSTR_re),          MP_ROM_PTR(&mp_module_ure) },       \
-    { MP_ROM_QSTR(MP_QSTR_json),        MP_ROM_PTR(&mp_module_ujson) },     \
-    { MP_ROM_QSTR(MP_QSTR_os),          MP_ROM_PTR(&mp_module_uos) },       \
-    { MP_ROM_QSTR(MP_QSTR_time),        MP_ROM_PTR(&mp_module_utime) },     \
-    { MP_ROM_QSTR(MP_QSTR_select),      MP_ROM_PTR(&mp_module_uselect) },   \
-    { MP_ROM_QSTR(MP_QSTR_socket),      MP_ROM_PTR(&mp_module_usocket) },   \
-    { MP_ROM_QSTR(MP_QSTR_binascii),    MP_ROM_PTR(&mp_module_ubinascii) }, \
-    { MP_ROM_QSTR(MP_QSTR_ssl),         MP_ROM_PTR(&mp_module_ussl) },      \
-    { MP_ROM_QSTR(MP_QSTR_machine),     MP_ROM_PTR(&machine_module) },      \
-
 // extra constants
 #define MICROPY_PORT_CONSTANTS \
     { MP_ROM_QSTR(MP_QSTR_umachine),     MP_ROM_PTR(&machine_module) },      \
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index 5c9d602ab..89e537347 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -212,24 +212,6 @@ extern const struct _mp_obj_module_t mp_module_onewire;
     { MP_OBJ_NEW_QSTR(MP_QSTR__onewire), (mp_obj_t)&mp_module_onewire }, \
     { MP_OBJ_NEW_QSTR(MP_QSTR_uhashlib), (mp_obj_t)&mp_module_uhashlib }, \
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_binascii), (mp_obj_t)&mp_module_ubinascii }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_collections), (mp_obj_t)&mp_module_collections }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_errno), (mp_obj_t)&mp_module_uerrno }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_hashlib), (mp_obj_t)&mp_module_uhashlib }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_heapq), (mp_obj_t)&mp_module_uheapq }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_io), (mp_obj_t)&mp_module_io }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_json), (mp_obj_t)&mp_module_ujson }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_os), (mp_obj_t)&uos_module }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_random), (mp_obj_t)&mp_module_urandom }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_re), (mp_obj_t)&mp_module_ure }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_select), (mp_obj_t)&mp_module_uselect }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_socket), (mp_obj_t)&mp_module_usocket }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_ssl), (mp_obj_t)&mp_module_ussl }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_struct), (mp_obj_t)&mp_module_ustruct }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_time), (mp_obj_t)&utime_module }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR_zlib), (mp_obj_t)&mp_module_uzlib }, \
-
 #define MP_STATE_PORT MP_STATE_VM
 
 struct _machine_timer_obj_t;
diff --git a/ports/esp8266/mpconfigport.h b/ports/esp8266/mpconfigport.h
index e77f88c83..726319392 100644
--- a/ports/esp8266/mpconfigport.h
+++ b/ports/esp8266/mpconfigport.h
@@ -167,23 +167,6 @@ extern const struct _mp_obj_module_t mp_module_onewire;
     { MP_ROM_QSTR(MP_QSTR_machine), MP_ROM_PTR(&mp_module_machine) }, \
     { MP_ROM_QSTR(MP_QSTR__onewire), MP_ROM_PTR(&mp_module_onewire) }, \
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_binascii), MP_ROM_PTR(&mp_module_ubinascii) }, \
-    { MP_ROM_QSTR(MP_QSTR_collections), MP_ROM_PTR(&mp_module_collections) }, \
-    { MP_ROM_QSTR(MP_QSTR_errno), MP_ROM_PTR(&mp_module_uerrno) }, \
-    { MP_ROM_QSTR(MP_QSTR_hashlib), MP_ROM_PTR(&mp_module_uhashlib) }, \
-    { MP_ROM_QSTR(MP_QSTR_io), MP_ROM_PTR(&mp_module_io) }, \
-    { MP_ROM_QSTR(MP_QSTR_json), MP_ROM_PTR(&mp_module_ujson) }, \
-    { MP_ROM_QSTR(MP_QSTR_os), MP_ROM_PTR(&uos_module) }, \
-    { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&mp_module_urandom) }, \
-    { MP_ROM_QSTR(MP_QSTR_re), MP_ROM_PTR(&mp_module_ure) }, \
-    { MP_ROM_QSTR(MP_QSTR_select), MP_ROM_PTR(&mp_module_uselect) }, \
-    { MP_ROM_QSTR(MP_QSTR_socket), MP_ROM_PTR(&mp_module_lwip) }, \
-    { MP_ROM_QSTR(MP_QSTR_ssl), MP_ROM_PTR(&mp_module_ussl) }, \
-    { MP_ROM_QSTR(MP_QSTR_struct), MP_ROM_PTR(&mp_module_ustruct) }, \
-    { MP_ROM_QSTR(MP_QSTR_time), MP_ROM_PTR(&utime_module) }, \
-    { MP_ROM_QSTR(MP_QSTR_zlib), MP_ROM_PTR(&mp_module_uzlib) }, \
-
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
diff --git a/ports/javascript/mpconfigport.h b/ports/javascript/mpconfigport.h
index 02d83f402..8ea43d84c 100644
--- a/ports/javascript/mpconfigport.h
+++ b/ports/javascript/mpconfigport.h
@@ -131,21 +131,6 @@ extern const struct _mp_obj_module_t mp_module_utime;
 #define MICROPY_PORT_BUILTIN_MODULES \
     { MP_ROM_QSTR(MP_QSTR_utime), MP_ROM_PTR(&mp_module_utime) }, \
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_binascii), MP_ROM_PTR(&mp_module_ubinascii) }, \
-    { MP_ROM_QSTR(MP_QSTR_collections), MP_ROM_PTR(&mp_module_collections) }, \
-    { MP_ROM_QSTR(MP_QSTR_re), MP_ROM_PTR(&mp_module_ure) }, \
-    { MP_ROM_QSTR(MP_QSTR_zlib), MP_ROM_PTR(&mp_module_uzlib) }, \
-    { MP_ROM_QSTR(MP_QSTR_json), MP_ROM_PTR(&mp_module_ujson) }, \
-    { MP_ROM_QSTR(MP_QSTR_heapq), MP_ROM_PTR(&mp_module_uheapq) }, \
-    { MP_ROM_QSTR(MP_QSTR_hashlib), MP_ROM_PTR(&mp_module_uhashlib) }, \
-    { MP_ROM_QSTR(MP_QSTR_io), MP_ROM_PTR(&mp_module_io) }, \
-    { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&mp_module_urandom) }, \
-    { MP_ROM_QSTR(MP_QSTR_time), MP_ROM_PTR(&mp_module_utime) }, \
-    { MP_ROM_QSTR(MP_QSTR_select), MP_ROM_PTR(&mp_module_uselect) }, \
-    { MP_ROM_QSTR(MP_QSTR_struct), MP_ROM_PTR(&mp_module_ustruct) }, \
-    { MP_ROM_QSTR(MP_QSTR_errno), MP_ROM_PTR(&mp_module_uerrno) }, \
-
 //#define MICROPY_EVENT_POLL_HOOK {ets_event_poll();}
 #if MICROPY_PY_THREAD
 #define MICROPY_EVENT_POLL_HOOK \
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index da9a03e1d..71f9f6804 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -281,10 +281,6 @@ extern const struct _mp_obj_module_t ble_module;
 
 #endif // BLUETOOTH_SD
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_os), MP_ROM_PTR(&mp_module_uos) }, \
-    { MP_ROM_QSTR(MP_QSTR_time), MP_ROM_PTR(&mp_module_utime) }, \
-
 // extra built in names to add to the global namespace
 #define MICROPY_PORT_BUILTINS \
     { MP_ROM_QSTR(MP_QSTR_help), MP_ROM_PTR(&mp_builtin_help_obj) }, \
diff --git a/ports/stm32/mpconfigport.h b/ports/stm32/mpconfigport.h
index 580675511..2cc37e3bf 100644
--- a/ports/stm32/mpconfigport.h
+++ b/ports/stm32/mpconfigport.h
@@ -223,21 +223,12 @@ extern const struct _mp_obj_module_t mp_module_onewire;
 #if MICROPY_PY_USOCKET && MICROPY_PY_LWIP
 // usocket implementation provided by lwIP
 #define SOCKET_BUILTIN_MODULE               { MP_ROM_QSTR(MP_QSTR_usocket), MP_ROM_PTR(&mp_module_lwip) },
-#define SOCKET_BUILTIN_MODULE_WEAK_LINKS    { MP_ROM_QSTR(MP_QSTR_socket), MP_ROM_PTR(&mp_module_lwip) },
 #elif MICROPY_PY_USOCKET
 // usocket implementation provided by skeleton wrapper
 #define SOCKET_BUILTIN_MODULE               { MP_ROM_QSTR(MP_QSTR_usocket), MP_ROM_PTR(&mp_module_usocket) },
-#define SOCKET_BUILTIN_MODULE_WEAK_LINKS    { MP_ROM_QSTR(MP_QSTR_socket), MP_ROM_PTR(&mp_module_usocket) },
 #else
 // no usocket module
 #define SOCKET_BUILTIN_MODULE
-#define SOCKET_BUILTIN_MODULE_WEAK_LINKS
-#endif
-
-#if MICROPY_PY_USSL
-#define SSL_BUILTIN_MODULE_WEAK_LINKS       { MP_ROM_QSTR(MP_QSTR_ssl), MP_ROM_PTR(&mp_module_ussl) },
-#else
-#define SSL_BUILTIN_MODULE_WEAK_LINKS
 #endif
 
 #if MICROPY_PY_NETWORK
@@ -263,25 +254,6 @@ extern const struct _mp_obj_module_t mp_module_onewire;
     BLUETOOTH_BUILTIN_MODULE \
     { MP_ROM_QSTR(MP_QSTR__onewire), MP_ROM_PTR(&mp_module_onewire) }, \
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_binascii), MP_ROM_PTR(&mp_module_ubinascii) }, \
-    { MP_ROM_QSTR(MP_QSTR_collections), MP_ROM_PTR(&mp_module_collections) }, \
-    { MP_ROM_QSTR(MP_QSTR_re), MP_ROM_PTR(&mp_module_ure) }, \
-    { MP_ROM_QSTR(MP_QSTR_zlib), MP_ROM_PTR(&mp_module_uzlib) }, \
-    { MP_ROM_QSTR(MP_QSTR_json), MP_ROM_PTR(&mp_module_ujson) }, \
-    { MP_ROM_QSTR(MP_QSTR_heapq), MP_ROM_PTR(&mp_module_uheapq) }, \
-    { MP_ROM_QSTR(MP_QSTR_hashlib), MP_ROM_PTR(&mp_module_uhashlib) }, \
-    { MP_ROM_QSTR(MP_QSTR_io), MP_ROM_PTR(&mp_module_io) }, \
-    { MP_ROM_QSTR(MP_QSTR_os), MP_ROM_PTR(&mp_module_uos) }, \
-    { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&mp_module_urandom) }, \
-    { MP_ROM_QSTR(MP_QSTR_time), MP_ROM_PTR(&mp_module_utime) }, \
-    { MP_ROM_QSTR(MP_QSTR_select), MP_ROM_PTR(&mp_module_uselect) }, \
-    SOCKET_BUILTIN_MODULE_WEAK_LINKS \
-    SSL_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_struct), MP_ROM_PTR(&mp_module_ustruct) }, \
-    { MP_ROM_QSTR(MP_QSTR_machine), MP_ROM_PTR(&machine_module) }, \
-    { MP_ROM_QSTR(MP_QSTR_errno), MP_ROM_PTR(&mp_module_uerrno) }, \
-
 // extra constants
 #define MICROPY_PORT_CONSTANTS \
     { MP_ROM_QSTR(MP_QSTR_umachine), MP_ROM_PTR(&machine_module) }, \
diff --git a/ports/zephyr/mpconfigport.h b/ports/zephyr/mpconfigport.h
index 0b35de35b..1ca357756 100644
--- a/ports/zephyr/mpconfigport.h
+++ b/ports/zephyr/mpconfigport.h
@@ -119,10 +119,8 @@ extern const struct _mp_obj_module_t mp_module_zsensor;
 
 #if MICROPY_PY_USOCKET
 #define MICROPY_PY_USOCKET_DEF { MP_ROM_QSTR(MP_QSTR_usocket), MP_ROM_PTR(&mp_module_usocket) },
-#define MICROPY_PY_USOCKET_WEAK_DEF { MP_ROM_QSTR(MP_QSTR_socket), MP_ROM_PTR(&mp_module_usocket) },
 #else
 #define MICROPY_PY_USOCKET_DEF
-#define MICROPY_PY_USOCKET_WEAK_DEF
 #endif
 
 #if MICROPY_PY_UTIME
@@ -150,10 +148,6 @@ extern const struct _mp_obj_module_t mp_module_zsensor;
     MICROPY_PY_ZEPHYR_DEF \
     MICROPY_PY_ZSENSOR_DEF \
 
-#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
-    { MP_ROM_QSTR(MP_QSTR_time), MP_ROM_PTR(&mp_module_time) }, \
-    MICROPY_PY_USOCKET_WEAK_DEF \
-
 // extra built in names to add to the global namespace
 #define MICROPY_PORT_BUILTINS \