Fix task key computation

src/prefect/tasks.py

@@ -6,7 +6,6 @@
 
 import datetime
 import inspect
-import os
 from copy import copy
 from functools import partial, update_wrapper
 from typing import (
@@ -188,6 +187,31 @@ def _infer_parent_task_runs(
     return parents
 
 
+def _generate_task_key(fn: Callable) -> str:
+    """Generate a task key based on the function name and source code.
+
+    We may eventually want some sort of top-level namespace here to
+    disambiguate tasks with the same function name in different modules,
+    in a more human-readable way, while avoiding relative import problems (see #12337).
+
+    As long as the task implementations are unique (even if named the same), we should
+    not have any collisions.
+
+    Args:
+        fn: The function to generate a task key for.
+    """
+    if not hasattr(fn, "__qualname__"):
+        return to_qualified_name(type(fn))
+
+    qualname = fn.__qualname__.split(".")[-1]
+
+    code_hash = (
+        h[:NUM_CHARS_DYNAMIC_KEY] if (h := hash_objects(fn.__code__)) else "unknown"
+    )
+
+    return f"{qualname}-{code_hash}"
+
+
 class Task(Generic[P, R]):
     """
     A Prefect task definition.
@@ -270,7 +294,7 @@ def __init__(
         description: Optional[str] = None,
         tags: Optional[Iterable[str]] = None,
         version: Optional[str] = None,
-        cache_policy: Optional[CachePolicy] = NotSet,
+        cache_policy: Union[CachePolicy, Type[NotSet]] = NotSet,
         cache_key_fn: Optional[
             Callable[["TaskRunContext", Dict[str, Any]], Optional[str]]
         ] = None,
@@ -369,17 +393,7 @@ def __init__(
 
         self.tags = set(tags if tags else [])
 
-        if not hasattr(self.fn, "__qualname__"):
-            self.task_key = to_qualified_name(type(self.fn))
-        else:
-            try:
-                task_origin_hash = hash_objects(
-                    self.name, os.path.abspath(inspect.getsourcefile(self.fn))
-                )
-            except TypeError:
-                task_origin_hash = "unknown-source-file"
-
-            self.task_key = f"{self.fn.__qualname__}-{task_origin_hash}"
+        self.task_key = _generate_task_key(self.fn)
 
         if cache_policy is not NotSet and cache_key_fn is not None:
             logger.warning(
@@ -1496,7 +1510,7 @@ async def serve(self) -> NoReturn:
 
         Args:
             task_runner: The task runner to use for serving the task. If not provided,
-                the default ConcurrentTaskRunner will be used.
+                the default task runner will be used.
 
         Examples:
             Serve a task using the default task runner
@@ -1523,7 +1537,7 @@ def task(
     description: Optional[str] = None,
     tags: Optional[Iterable[str]] = None,
     version: Optional[str] = None,
-    cache_policy: CachePolicy = NotSet,
+    cache_policy: Union[CachePolicy, Type[NotSet]] = NotSet,
     cache_key_fn: Optional[
         Callable[["TaskRunContext", Dict[str, Any]], Optional[str]]
     ] = None,
@@ -1561,7 +1575,9 @@ def task(
     tags: Optional[Iterable[str]] = None,
     version: Optional[str] = None,
     cache_policy: Union[CachePolicy, Type[NotSet]] = NotSet,
-    cache_key_fn: Callable[["TaskRunContext", Dict[str, Any]], Optional[str]] = None,
+    cache_key_fn: Union[
+        Callable[["TaskRunContext", Dict[str, Any]], Optional[str]], None
+    ] = None,
     cache_expiration: Optional[datetime.timedelta] = None,
     task_run_name: Optional[Union[Callable[[], str], str]] = None,
     retries: Optional[int] = None,

tests/events/client/instrumentation/test_task_run_state_change_events.py

@@ -60,11 +60,7 @@ def happy_path():
         == task_run.expected_start_time
     )
     assert pending.payload["task_run"].pop("estimated_start_time_delta") > 0.0
-    assert (
-        pending.payload["task_run"]
-        .pop("task_key")
-        .startswith("test_task_state_change_happy_path.<locals>.happy_little_tree")
-    )
+    assert pending.payload["task_run"].pop("task_key").startswith("happy_little_tree")
     assert pending.payload == {
         "initial_state": None,
         "intended": {"from": None, "to": "PENDING"},
@@ -112,11 +108,7 @@ def happy_path():
         == task_run.expected_start_time
     )
     assert running.payload["task_run"].pop("estimated_start_time_delta") > 0.0
-    assert (
-        running.payload["task_run"]
-        .pop("task_key")
-        .startswith("test_task_state_change_happy_path.<locals>.happy_little_tree")
-    )
+    assert running.payload["task_run"].pop("task_key").startswith("happy_little_tree")
     assert running.payload == {
         "intended": {"from": "PENDING", "to": "RUNNING"},
         "initial_state": {
@@ -169,11 +161,7 @@ def happy_path():
         == task_run.expected_start_time
     )
     assert completed.payload["task_run"].pop("estimated_start_time_delta") > 0.0
-    assert (
-        completed.payload["task_run"]
-        .pop("task_key")
-        .startswith("test_task_state_change_happy_path.<locals>.happy_little_tree")
-    )
+    assert completed.payload["task_run"].pop("task_key").startswith("happy_little_tree")
     assert completed.payload["task_run"].pop("estimated_run_time") > 0.0
     assert (
         pendulum.parse(completed.payload["task_run"].pop("start_time"))
@@ -262,11 +250,7 @@ def happy_path():
         == task_run.expected_start_time
     )
     assert pending.payload["task_run"].pop("estimated_start_time_delta") > 0.0
-    assert (
-        pending.payload["task_run"]
-        .pop("task_key")
-        .startswith("test_task_state_change_task_failure.<locals>.happy_little_tree")
-    )
+    assert pending.payload["task_run"].pop("task_key").startswith("happy_little_tree")
     assert pending.payload == {
         "initial_state": None,
         "intended": {"from": None, "to": "PENDING"},
@@ -314,11 +298,7 @@ def happy_path():
         == task_run.expected_start_time
     )
     assert running.payload["task_run"].pop("estimated_start_time_delta") > 0.0
-    assert (
-        running.payload["task_run"]
-        .pop("task_key")
-        .startswith("test_task_state_change_task_failure.<locals>.happy_little_tree")
-    )
+    assert running.payload["task_run"].pop("task_key").startswith("happy_little_tree")
     assert running.payload == {
         "intended": {"from": "PENDING", "to": "RUNNING"},
         "initial_state": {
@@ -374,11 +354,7 @@ def happy_path():
         == task_run.expected_start_time
     )
     assert failed.payload["task_run"].pop("estimated_start_time_delta") > 0.0
-    assert (
-        failed.payload["task_run"]
-        .pop("task_key")
-        .startswith("test_task_state_change_task_failure.<locals>.happy_little_tree")
-    )
+    assert failed.payload["task_run"].pop("task_key").startswith("happy_little_tree")
     assert failed.payload["task_run"].pop("estimated_run_time") > 0.0
     assert (
         pendulum.parse(failed.payload["task_run"].pop("start_time"))

tests/test_background_tasks.py

@@ -1,6 +1,4 @@
 import asyncio
-import inspect
-import os
 from datetime import timedelta
 from pathlib import Path
 from typing import TYPE_CHECKING, AsyncGenerator, Iterable, Tuple
@@ -26,7 +24,6 @@
     temporary_settings,
 )
 from prefect.task_worker import TaskWorker
-from prefect.utilities.hashing import hash_objects
 
 if TYPE_CHECKING:
     from prefect.client.orchestration import PrefectClient
@@ -447,22 +444,3 @@ async def bar(x: int, mappable: Iterable) -> Tuple[int, Iterable]:
                 "parameters": {"x": i + 1, "mappable": ["some", "iterable"]},
                 "context": mock.ANY,
             }
-
-
-class TestTaskKey:
-    def test_task_key_includes_qualname_and_source_file_hash(self):
-        def some_fn():
-            pass
-
-        t = Task(fn=some_fn)
-        source_file = os.path.abspath(inspect.getsourcefile(some_fn))
-        task_origin_hash = hash_objects(t.name, source_file)
-        assert t.task_key == f"{some_fn.__qualname__}-{task_origin_hash}"
-
-    def test_task_key_handles_unknown_source_file(self, monkeypatch):
-        def some_fn():
-            pass
-
-        monkeypatch.setattr(inspect, "getsourcefile", lambda x: None)
-        t = Task(fn=some_fn)
-        assert t.task_key == f"{some_fn.__qualname__}-unknown-source-file"

tests/test_tasks.py

@@ -102,6 +102,20 @@ def my_task():
         assert my_task.name == "another_name"
 
 
+class TestTaskKey:
+    def test_task_key_typical_case(self):
+        @task
+        def my_task():
+            pass
+
+        assert my_task.task_key.startswith("my_task-")
+
+    def test_task_key_after_import(self):
+        from tests.generic_tasks import noop
+
+        assert noop.task_key.startswith("noop-")
+
+
 class TestTaskRunName:
     def test_run_name_default(self):
         @task