fixtures: announce fixture setup before execution (#13169)

AUTHORS

@@ -466,6 +466,7 @@ Simon Holesch
 Simon Kerr
 Skylar Downes
 Srinivas Reddy Thatiparthy
+Stamatis-Christos Saridakis
 Stefaan Lippens
 Stefan Farmbauer
 Stefan Scherfke

changelog/13169.improvement.rst

@@ -0,0 +1,2 @@
+When using ``--setup-show`` or ``--setup-only``, show a ``SETUP START``
+line before each fixture starts executing, so a stalled fixture setup can be identified.

src/_pytest/setuponly.py

@@ -32,6 +32,9 @@ def pytest_addoption(parser: Parser) -> None:
 def pytest_fixture_setup(
     fixturedef: FixtureDef[object], request: SubRequest
 ) -> Generator[None, object, object]:
+    if request.config.option.setupshow:
+        # Report this fixture before entering user code, including if it hangs.
+        _show_fixture_action(fixturedef, request.config, "SETUP START", end_line=True)
     try:
         return (yield)
     finally:
@@ -62,7 +65,7 @@ def pytest_fixture_post_finalizer(
 
 
 def _show_fixture_action(
-    fixturedef: FixtureDef[object], config: Config, msg: str
+    fixturedef: FixtureDef[object], config: Config, msg: str, *, end_line: bool = False
 ) -> None:
     capman = config.pluginmanager.getplugin("capturemanager")
     if capman:
@@ -85,7 +88,11 @@ def _show_fixture_action(
     if hasattr(fixturedef, "cached_param"):
         tw.write(f"[{saferepr(fixturedef.cached_param, maxsize=42)}]")
 
-    tw.flush()
+    # End the early marker before any output from the fixture body.
+    if end_line:
+        tw.line()
+    else:
+        tw.flush()
 
     if capman:
         capman.resume_global_capture()

testing/python/fixtures.py

@@ -4626,10 +4626,14 @@ def test_second(my_fixture):
     result.stdout.fnmatch_lines(
         [
             "test_fixtures.py::test_first ",
+            "        SETUP START F my_fixture",
+            "",
             "        SETUP    F my_fixture",
             "        test_fixtures.py::test_first (fixtures used: my_fixture, request) PASSED",
             "test_fixtures.py::test_first ERROR",
             "test_fixtures.py::test_second ",
+            "        SETUP START F my_fixture",
+            "",
             "        SETUP    F my_fixture",
             "        test_fixtures.py::test_second (fixtures used: my_fixture, request) PASSED",
             "        TEARDOWN F my_fixture",

testing/test_setuponly.py

@@ -8,6 +8,75 @@
 import pytest
 
 
+@pytest.mark.parametrize("mode", ["--setup-show", "--setup-only"])
+def test_setup_show_announces_fixture_before_body(
+    pytester: Pytester, mode: str
+) -> None:
+    p = pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.fixture(params=["example"], ids=["sample"])
+        def slow():
+            print("BODY-ENTERED", flush=True)
+            yield "value"
+
+        def test_value(slow):
+            assert slow == "value"
+        """
+    )
+
+    result = pytester.runpytest(mode, "-s", p)
+    assert result.ret == 0
+    output = result.stdout.str()
+    assert "SETUP START F slow" in output
+    assert "SETUP    F slow['sample']" in output
+    assert "TEARDOWN F slow['sample']" in output
+    assert output.index("SETUP START F slow") < output.index("BODY-ENTERED")
+    assert output.index("BODY-ENTERED") < output.index("SETUP    F slow")
+    assert "SETUP START F slow\n" in output
+
+
+def test_setup_show_announces_failed_fixture(pytester: Pytester) -> None:
+    p = pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.fixture
+        def broken():
+            raise ValueError("fixture setup failed")
+
+        def test_failure(broken):
+            pass
+        """
+    )
+
+    result = pytester.runpytest("--setup-show", p)
+    assert result.ret == 1
+    output = result.stdout.str()
+    assert "SETUP START F broken" in output
+    assert "SETUP    F broken" in output
+    assert output.index("SETUP START F broken") < output.index("SETUP    F broken")
+
+
+def test_no_setup_start_when_not_requested(pytester: Pytester) -> None:
+    p = pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.fixture
+        def normal():
+            return 1
+
+        def test_normal(normal):
+            assert normal == 1
+        """
+    )
+    result = pytester.runpytest(p)
+    assert result.ret == 0
+    assert "SETUP START" not in result.stdout.str()
+
+
 @pytest.fixture(params=["--setup-only", "--setup-plan", "--setup-show"], scope="module")
 def mode(request):
     return request.param