pybricks.tools: Fix race=False in multitask().

Fix wrong index direction for fetching the race keyword argument in
pb_type_Task_new().

n_args - 1 would be the last positional argument, n_args would be the
race keyword itself and n_args + 1 is the value of the race keyword
argument, which is what we want.

Also add a test to verify that it is working as expected.

Author: dlech

CHANGELOG.md

@@ -8,10 +8,12 @@
 - Make 3D orientation default for heading and drivebase heading control ([support#1962]).
 
 ### Fixed
+- Fixed `race=False` ignored in `pybricks.tools.multitask()`. ([support#2468])
 - Fixed Essential Hub button being disabled after power off so it could not be
   switched on again.
 
 [support#1962]: https://github.com/pybricks/support/issues/1962
+[support#2468]: https://github.com/pybricks/support/issues/2468
 
 ## [4.0.0b2] - 2025-11-25
 
@@ -22,7 +24,7 @@
 
 ### Added
 - Experimental support for USB connectivity on SPIKE Prime ([pybricks-micropython#208]). Currently disabled by default.
-- Initial support for `pybricks.iodevices.UARTDevice` ([support#220]). 
+- Initial support for `pybricks.iodevices.UARTDevice` ([support#220]).
 - Enabled previously hidden support for multiple code
   slots ([pybricks-micropython#264], [pybricks-micropython#312]).
 - Added the following status flags to the Pybricks protocol:
@@ -185,7 +187,7 @@
 - Fixed battery charging timeout if it didn't reach 100% after about 6 hours.
   This is same behavior observed in official firmware. ([pybricks-micropython#292]).
 - Fixed inconsistent battery level reported to user. Now it uses the same value
-  as used by the light indicator ([support#2055]). 
+  as used by the light indicator ([support#2055]).
 - Fixed `DriveBase.angle()` getting an incorrectly rounded gyro value, which
   could cause `turn(360)` to be off by a degree ([support#1844]).
 - Fixed `hub` silently ignoring non-orthogonal base axis when it should raise.

pybricks/tools/pb_type_task.c

@@ -138,7 +138,7 @@ MP_DEFINE_CONST_DICT(pb_type_Task_locals_dict, pb_type_Task_locals_dict_table);
 static mp_obj_t pb_type_Task_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
 
     // Whether to race until one task is done (True) or wait for all tasks (False).
-    bool race = n_kw == 1 && mp_obj_is_true(args[n_args - 1]);
+    bool race = n_kw == 1 && mp_obj_is_true(args[n_args + 1]);
 
     pb_type_Task_obj_t *self = mp_obj_malloc(pb_type_Task_obj_t, type);
     self->num_tasks = n_args;

tests/virtualhub/multitasking/basic.py

@@ -163,11 +163,40 @@ async def test_race_2():
         print(type(e), e.args)
 
 
+async def test_race_false():
+    print("test_race_false")
+
+    task1_cancel = CallCounter()
+    task2_cancel = CallCounter()
+
+    task1 = return_after(1, task1_cancel)
+    task2 = return_after(2, task2_cancel)
+
+    # returns [0, 1] - both allowed to complete
+    print(await multitask(task1, task2, race=False))
+
+    # neither should be canceled
+    print(task1_cancel.count, task2_cancel.count)
+
+    # both should raise StopIteration because they are done
+
+    try:
+        next(task1)
+    except StopIteration as e:
+        print(type(e), e.args)
+
+    try:
+        next(task2)
+    except StopIteration as e:
+        print(type(e), e.args)
+
+
 async def main():
     await test_all_1()
     await test_all_2()
     await test_race_1()
     await test_race_2()
+    await test_race_false()
 
 
 run_task(main())

tests/virtualhub/multitasking/basic.py.exp

@@ -18,3 +18,8 @@ test_race_2
 1 0
 <class 'StopIteration'> ()
 <class 'StopIteration'> ()
+test_race_false
+(0, 1)
+0 0
+<class 'StopIteration'> ()
+<class 'StopIteration'> ()