fix #544: Correctly pass StopIteration trough wrappers

Raising a StopIteration in a generator triggers a RuntimeError.
If the RuntimeError of a generator has the passed in StopIteration as cause
resume with that StopIteration as normal exception instead of failing with the RuntimeError.

Author: RonnyPfannschmidt

changelog/544.bugfix.rst

@@ -0,0 +1,6 @@
+Correctly pass :class:`StopIteration` trough hook wrappers.
+
+Raising a :class:`StopIteration` in a generator triggers a :class:`RuntimeError`.
+
+If the :class:`RuntimeError` of a generator has the passed in :class:`StopIteration` as cause
+resume with that :class:`StopIteration` as normal exception instead of failing with the :class:`RuntimeError`.

src/pluggy/_callers.py

@@ -119,7 +119,19 @@ def _multicall(
             for teardown in reversed(teardowns):
                 try:
                     if exception is not None:
-                        teardown.throw(exception)  # type: ignore[union-attr]
+                        try:
+                            teardown.throw(exception)  # type: ignore[union-attr]
+                        except RuntimeError as re:
+                            # StopIteration from generator causes RuntimeError
+                            # even for coroutine usage - see #544
+                            if (
+                                isinstance(exception, StopIteration)
+                                and re.__cause__ is exception
+                            ):
+                                teardown.close()  # type: ignore[union-attr]
+                                continue
+                            else:
+                                raise
                     else:
                         teardown.send(result)  # type: ignore[union-attr]
                     # Following is unreachable for a well behaved hook wrapper.
@@ -164,7 +176,19 @@ def _multicall(
                 else:
                     try:
                         if outcome._exception is not None:
-                            teardown.throw(outcome._exception)
+                            try:
+                                teardown.throw(outcome._exception)
+                            except RuntimeError as re:
+                                # StopIteration from generator causes RuntimeError
+                                # even for coroutine usage - see #544
+                                if (
+                                    isinstance(outcome._exception, StopIteration)
+                                    and re.__cause__ is outcome._exception
+                                ):
+                                    teardown.close()
+                                    continue
+                                else:
+                                    raise
                         else:
                             teardown.send(outcome._result)
                         # Following is unreachable for a well behaved hook wrapper.

testing/test_multicall.py

@@ -416,6 +416,36 @@ def m2():
     ]
 
 
+@pytest.mark.parametrize("has_hookwrapper", [True, False])
+def test_wrapper_stopiteration_passtrough(has_hookwrapper: bool) -> None:
+    out = []
+
+    @hookimpl(wrapper=True)
+    def wrap():
+        out.append("wrap")
+        try:
+            yield
+        finally:
+            out.append("wrap done")
+
+    @hookimpl(wrapper=not has_hookwrapper, hookwrapper=has_hookwrapper)
+    def wrap_path2():
+        yield
+
+    @hookimpl
+    def stop():
+        out.append("stop")
+        raise StopIteration
+
+    with pytest.raises(StopIteration):
+        try:
+            MC([stop, wrap, wrap_path2], {})
+        finally:
+            out.append("finally")
+
+    assert out == ["wrap", "stop", "wrap done", "finally"]
+
+
 def test_suppress_inner_wrapper_teardown_exc() -> None:
     out = []