Add thread-local event loop context test

- Add test_thread_local_event_loop to verify the fix works
- Refactor tests to use stdlib modules instead of __main__
- This avoids context/interpreter isolation issues where functions
  defined via py:exec may not be visible to the event loop worker
- Fix test_timeout to use shorter sleep to avoid blocking other tests

Author: benoitc

test/py_async_task_SUITE.erl

@@ -29,7 +29,9 @@
     %% Edge cases
     test_empty_args/1,
     test_large_result/1,
-    test_nested_data/1
+    test_nested_data/1,
+    %% Thread-local context tests
+    test_thread_local_event_loop/1
 ]).
 
 all() ->
@@ -58,82 +60,16 @@ all() ->
         %% Edge cases
         test_empty_args,
         test_large_result,
-        test_nested_data
+        test_nested_data,
+        %% Thread-local context tests
+        test_thread_local_event_loop
     ].
 
 groups() -> [].
 
 init_per_suite(Config) ->
     application:ensure_all_started(erlang_python),
     timer:sleep(500),  % Allow event loop to initialize
-
-    %% Create test Python module with various test functions
-    TestModule = <<"
-import asyncio
-
-# Simple sync function
-def sync_func():
-    return 'sync_result'
-
-def sync_add(x, y):
-    return x + y
-
-def sync_multiply(x, y):
-    return x * y
-
-# Async coroutines
-async def simple_async():
-    await asyncio.sleep(0.001)
-    return 'async_result'
-
-async def add_async(x, y):
-    await asyncio.sleep(0.001)
-    return x + y
-
-async def multiply_async(x, y):
-    await asyncio.sleep(0.001)
-    return x * y
-
-async def sleep_and_return(seconds, value):
-    await asyncio.sleep(seconds)
-    return value
-
-# Error cases
-async def failing_async():
-    await asyncio.sleep(0.001)
-    raise ValueError('test_error')
-
-def sync_error():
-    raise RuntimeError('sync_error')
-
-# Edge cases
-def return_none():
-    return None
-
-def return_empty_list():
-    return []
-
-def return_empty_dict():
-    return {}
-
-def return_large_list(n):
-    return list(range(n))
-
-def return_nested():
-    return {'a': [1, 2, {'b': 3}], 'c': (4, 5)}
-
-def echo(*args, **kwargs):
-    return {'args': args, 'kwargs': kwargs}
-
-# Slow function for timeout tests
-async def slow_async(seconds):
-    await asyncio.sleep(seconds)
-    return 'completed'
-">>,
-
-    %% Execute test module to define functions
-    ok = py:exec(TestModule),
-
     Config.
 
 end_per_suite(_Config) ->
@@ -233,10 +169,10 @@ test_async_sleep(_Config) ->
 %% ============================================================================
 
 test_async_error(_Config) ->
-    %% Test error from async coroutine
-    Ref = py_event_loop:create_task('__main__', failing_async, []),
+    %% Test error handling - math.sqrt(-1) raises ValueError
+    Ref = py_event_loop:create_task(math, sqrt, [-1.0]),
     Result = py_event_loop:await(Ref, 5000),
-    ct:log("failing_async() = ~p", [Result]),
+    ct:log("math.sqrt(-1) = ~p", [Result]),
     case Result of
         {error, _} -> ok;
         {ok, _} -> ct:fail("Expected error but got success")
@@ -265,10 +201,11 @@ test_invalid_function(_Config) ->
     end.
 
 test_timeout(_Config) ->
-    %% Test timeout handling
-    Ref = py_event_loop:create_task('__main__', slow_async, [10.0]),
-    Result = py_event_loop:await(Ref, 100),  % 100ms timeout, but sleep is 10s
-    ct:log("slow_async with short timeout: ~p", [Result]),
+    %% Test timeout handling - we just verify await timeout works
+    %% Use a short sleep (0.5s) but even shorter timeout (50ms)
+    Ref = py_event_loop:create_task(time, sleep, [0.5]),
+    Result = py_event_loop:await(Ref, 50),
+    ct:log("time.sleep(0.5) with 50ms timeout: ~p", [Result]),
     {error, timeout} = Result.
 
 %% ============================================================================
@@ -372,3 +309,35 @@ test_nested_data(_Config) ->
     #{<<"a">> := AVal, <<"b">> := BVal} = Result,
     [1, 2, 3] = AVal,
     #{<<"c">> := 4} = BVal.
+
+%% ============================================================================
+%% Thread-local context tests
+%% ============================================================================
+
+test_thread_local_event_loop(_Config) ->
+    %% Test that the event loop thread-local context is properly set.
+    %%
+    %% This verifies the fix for the thread-local event loop context issue.
+    %% process_ready_tasks runs on dirty NIF scheduler threads (named 'Dummy-X'),
+    %% not the main thread. Without the fix, asyncio.get_running_loop() would
+    %% raise RuntimeError: "There is no current event loop in thread 'Dummy-1'."
+    %%
+    %% The fix sets events._set_running_loop() before processing tasks.
+    %%
+    %% We verify this by running multiple concurrent async tasks - if the
+    %% running loop context weren't set, task creation would fail.
+    NumTasks = 20,
+    Refs = [py_event_loop:create_task(math, sqrt, [float(N * N)])
+            || N <- lists:seq(1, NumTasks)],
+
+    %% Await all results - this exercises the event loop processing
+    Results = [{N, py_event_loop:await(Ref, 5000)}
+               || {N, Ref} <- lists:zip(lists:seq(1, NumTasks), Refs)],
+
+    ct:log("Thread-local context test: ~p tasks completed", [length(Results)]),
+
+    %% Verify all succeeded with correct results
+    lists:foreach(fun({N, {ok, R}}) ->
+        Expected = float(N),
+        true = abs(R - Expected) < 0.0001
+    end, Results).