Implement MypyItem.collect for pytest < 6.0

Author: dmtucker

src/pytest_mypy.py

@@ -145,6 +145,13 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.add_marker(self.MARKER)
 
+    def collect(self):
+        """
+        Partially work around https://github.com/pytest-dev/pytest/issues/8016
+        for pytest < 6.0 with --looponfail.
+        """
+        yield self
+
     @classmethod
     def from_parent(cls, *args, **kwargs):
         """Override from_parent for compatibility."""

tests/test_pytest_mypy.py

@@ -1,9 +1,13 @@
 import signal
 import textwrap
 
+import pexpect
 import pytest
 
 
+PYTEST_VERSION = tuple(int(v) for v in pytest.__version__.split(".")[:2])
+
+
 @pytest.fixture(
     params=[
         True,  # xdist enabled, active
@@ -309,7 +313,8 @@ def pyfunc(x):
     assert result.ret != 0
 
 
-def test_looponfail(testdir):
+@pytest.mark.parametrize("module_name", ["__init__", "test_demo"])
+def test_looponfail(testdir, module_name):
     """Ensure that the plugin works with --looponfail."""
 
     pass_source = textwrap.dedent(
@@ -324,7 +329,7 @@ def pyfunc(x: int) -> str:
             return x * 2
         """,
     )
-    pyfile = testdir.makepyfile(fail_source)
+    pyfile = testdir.makepyfile(**{module_name: fail_source})
     looponfailroot = testdir.mkdir("looponfailroot")
     looponfailroot_pyfile = looponfailroot.join(pyfile.basename)
     pyfile.move(looponfailroot_pyfile)
@@ -345,6 +350,14 @@ def pyfunc(x: int) -> str:
         expect_timeout=30.0,
     )
 
+    num_tests = 2
+    if module_name == "__init__" and (3, 10) <= PYTEST_VERSION < (6, 2):
+        # https://github.com/pytest-dev/pytest/issues/8016
+        # Pytest had a bug where it assumed only a Package would have a basename of
+        # __init__.py. In this test, Pytest mistakes MypyFile for a Package and
+        # returns after collecting only one object (the MypyFileItem).
+        num_tests = 1
+
     def _expect_session():
         child.expect("==== test session starts ====")
 
@@ -353,10 +366,11 @@ def _expect_failure():
         child.expect("==== FAILURES ====")
         child.expect(pyfile.basename + " ____")
         child.expect("2: error: Incompatible return value")
-        # These only show with mypy>=0.730:
-        # child.expect("==== mypy ====")
-        # child.expect("Found 1 error in 1 file (checked 1 source file)")
-        child.expect("2 failed")
+        # if num_tests == 2:
+        #     # These only show with mypy>=0.730:
+        #     child.expect("==== mypy ====")
+        #     child.expect("Found 1 error in 1 file (checked 1 source file)")
+        child.expect(str(num_tests) + " failed")
         child.expect("#### LOOPONFAILING ####")
         _expect_waiting()
 
@@ -375,10 +389,27 @@ def _expect_changed():
     def _expect_success():
         for _ in range(2):
             _expect_session()
-            # These only show with mypy>=0.730:
-            # child.expect("==== mypy ====")
-            # child.expect("Success: no issues found in 1 source file")
-            child.expect("2 passed")
+            # if num_tests == 2:
+            #     # These only show with mypy>=0.730:
+            #     child.expect("==== mypy ====")
+            #     child.expect("Success: no issues found in 1 source file")
+            try:
+                child.expect(str(num_tests) + " passed")
+            except pexpect.exceptions.TIMEOUT:
+                if module_name == "__init__" and (6, 0) <= PYTEST_VERSION < (6, 2):
+                    # MypyItems hit the __init__.py bug too when --looponfail
+                    # re-collects them after the failing file is modified.
+                    # Unlike MypyFile, MypyItem is not a Collector, so this used
+                    # to cause an AttributeError until a workaround was added
+                    # (MypyItem.collect was defined to yield itself).
+                    # Mypy probably noticed the __init__.py problem during the
+                    # development of Pytest 6.0, but the error was addressed
+                    # with an isinstance assertion, which broke the workaround.
+                    # Here, we hit that assertion:
+                    child.expect("AssertionError")
+                    child.expect("1 error")
+                    pytest.xfail("https://github.com/pytest-dev/pytest/issues/8016")
+                raise
         _expect_waiting()
 
     def _break():
@@ -391,3 +422,27 @@ def _break():
     _break()
     _fix()
     child.kill(signal.SIGTERM)
+
+
+def test_mypy_item_collect(testdir, xdist_args):
+    """Ensure coverage for a 3.10<=pytest<6.0 workaround."""
+    testdir.makepyfile(
+        """
+        def test_mypy_item_collect(request):
+            plugin = request.config.pluginmanager.getplugin("mypy")
+            mypy_items = [
+                item
+                for item in request.session.items
+                if isinstance(item, plugin.MypyItem)
+            ]
+            assert mypy_items
+            for mypy_item in mypy_items:
+                assert all(item is mypy_item for item in mypy_item.collect())
+        """,
+    )
+    result = testdir.runpytest_subprocess("--mypy", *xdist_args)
+    test_count = 1
+    mypy_file_checks = 1
+    mypy_status_check = 1
+    result.assert_outcomes(passed=test_count + mypy_file_checks + mypy_status_check)
+    assert result.ret == 0