Clarify mark.__getattr__

src/_pytest/mark/structures.py

@@ -291,23 +291,9 @@ class MarkGenerator(object):
             raise AttributeError("Marker name must NOT start with underscore")
 
         if self._config is not None:
-            self._update_markers(name)
-            if name not in self._markers:
-                warnings.warn(
-                    "Unknown pytest.mark.%s - is this a typo?  You can register "
-                    "custom marks to avoid this warning - for details, see "
-                    "https://docs.pytest.org/en/latest/mark.html" % name,
-                    UnknownMarkWarning,
-                )
-                if self._config.option.strict:
-                    fail("{!r} not a registered marker".format(name), pytrace=False)
-
-        return MarkDecorator(Mark(name, (), {}))
-
-    def _update_markers(self, name):
-        # We store a set of registered markers as a performance optimisation,
-        # but more could be added to `self._config` by other plugins at runtime.
-        # If we see an unknown marker, we therefore update the set and try again!
+            # We store a set of markers as a performance optimisation - if a mark
+            # name is in the set we definitely know it, but a mark may be known and
+            # not in the set.  We therefore start by updating the set!
             if name not in self._markers:
                 for line in self._config.getini("markers"):
                     # example lines: "skipif(condition): skip the given test if..."
@@ -316,6 +302,21 @@ class MarkGenerator(object):
                     marker = line.split(":")[0].split("(")[0].strip()
                     self._markers.add(marker)
 
+            # If the name is not in the set of known marks after updating,
+            # then it really is time to issue a warning or an error.
+            if name not in self._markers:
+                if self._config.option.strict:
+                    fail("{!r} not a registered marker".format(name), pytrace=False)
+                else:
+                    warnings.warn(
+                        "Unknown pytest.mark.%s - is this a typo?  You can register "
+                        "custom marks to avoid this warning - for details, see "
+                        "https://docs.pytest.org/en/latest/mark.html" % name,
+                        UnknownMarkWarning,
+                    )
+
+        return MarkDecorator(Mark(name, (), {}))
+
 
 MARK_GEN = MarkGenerator()