Add a typing-compatible mechanism for ad-hoc attributes on various objects

pytest has several instances where plugins set their own attributes on
objects they receive in hooks, like nodes and config. Since plugins are
detached from these object's definition by design, this causes a problem
for type checking because these attributes are not defined and mypy
complains.

Fix this by giving these objects a "store" which can be used by plugins
in a type-safe manner.

Currently this mechanism is private. We can consider exposing it at a
later point.

1 files changed, 20 insertions, 14 deletions

diff --git a/src/_pytest/skipping.py b/src/_pytest/skipping.py
index f70ef7f59..fe8742c66 100644
--- a/src/_pytest/skipping.py
+++ b/src/_pytest/skipping.py
@@ -4,6 +4,12 @@ from _pytest.mark.evaluate import MarkEvaluator
 from _pytest.outcomes import fail
 from _pytest.outcomes import skip
 from _pytest.outcomes import xfail
+from _pytest.store import StoreKey
+
+
+skipped_by_mark_key = StoreKey[bool]()
+evalxfail_key = StoreKey[MarkEvaluator]()
+unexpectedsuccess_key = StoreKey[str]()
 
 
 def pytest_addoption(parser):
@@ -68,14 +74,14 @@ def pytest_configure(config):
 @hookimpl(tryfirst=True)
 def pytest_runtest_setup(item):
     # Check if skip or skipif are specified as pytest marks
-    item._skipped_by_mark = False
+    item._store[skipped_by_mark_key] = False
     eval_skipif = MarkEvaluator(item, "skipif")
     if eval_skipif.istrue():
-        item._skipped_by_mark = True
+        item._store[skipped_by_mark_key] = True
         skip(eval_skipif.getexplanation())
 
     for skip_info in item.iter_markers(name="skip"):
-        item._skipped_by_mark = True
+        item._store[skipped_by_mark_key] = True
         if "reason" in skip_info.kwargs:
             skip(skip_info.kwargs["reason"])
         elif skip_info.args:
@@ -83,7 +89,7 @@ def pytest_runtest_setup(item):
         else:
             skip("unconditional skip")
 
-    item._evalxfail = MarkEvaluator(item, "xfail")
+    item._store[evalxfail_key] = MarkEvaluator(item, "xfail")
     check_xfail_no_run(item)
 
 
@@ -99,7 +105,7 @@ def pytest_pyfunc_call(pyfuncitem):
 def check_xfail_no_run(item):
     """check xfail(run=False)"""
     if not item.config.option.runxfail:
-        evalxfail = item._evalxfail
+        evalxfail = item._store[evalxfail_key]
         if evalxfail.istrue():
             if not evalxfail.get("run", True):
                 xfail("[NOTRUN] " + evalxfail.getexplanation())
@@ -107,12 +113,12 @@ def check_xfail_no_run(item):
 
 def check_strict_xfail(pyfuncitem):
     """check xfail(strict=True) for the given PASSING test"""
-    evalxfail = pyfuncitem._evalxfail
+    evalxfail = pyfuncitem._store[evalxfail_key]
     if evalxfail.istrue():
         strict_default = pyfuncitem.config.getini("xfail_strict")
         is_strict_xfail = evalxfail.get("strict", strict_default)
         if is_strict_xfail:
-            del pyfuncitem._evalxfail
+            del pyfuncitem._store[evalxfail_key]
             explanation = evalxfail.getexplanation()
             fail("[XPASS(strict)] " + explanation, pytrace=False)
 
@@ -121,12 +127,12 @@ def check_strict_xfail(pyfuncitem):
 def pytest_runtest_makereport(item, call):
     outcome = yield
     rep = outcome.get_result()
-    evalxfail = getattr(item, "_evalxfail", None)
-    # unittest special case, see setting of _unexpectedsuccess
-    if hasattr(item, "_unexpectedsuccess") and rep.when == "call":
-
-        if item._unexpectedsuccess:
-            rep.longrepr = "Unexpected success: {}".format(item._unexpectedsuccess)
+    evalxfail = item._store.get(evalxfail_key, None)
+    # unittest special case, see setting of unexpectedsuccess_key
+    if unexpectedsuccess_key in item._store and rep.when == "call":
+        reason = item._store[unexpectedsuccess_key]
+        if reason:
+            rep.longrepr = "Unexpected success: {}".format(reason)
         else:
             rep.longrepr = "Unexpected success"
         rep.outcome = "failed"
@@ -154,7 +160,7 @@ def pytest_runtest_makereport(item, call):
                 rep.outcome = "passed"
                 rep.wasxfail = explanation
     elif (
-        getattr(item, "_skipped_by_mark", False)
+        item._store.get(skipped_by_mark_key, True)
         and rep.skipped
         and type(rep.longrepr) is tuple
     ):