Fix some issues related to "-p no:X" with default_plugins

src/_pytest/config/__init__.py

@@ -762,7 +762,7 @@ class Config(object):
         by the importhook.
         """
         ns, unknown_args = self._parser.parse_known_and_unknown_args(args)
-        mode = ns.assertmode
+        mode = getattr(ns, "assertmode", "plain")
         if mode == "rewrite":
             try:
                 hook = _pytest.assertion.install_importhook(self)

src/_pytest/main.py

@@ -548,7 +548,7 @@ class Session(nodes.FSCollector):
         # Start with a Session root, and delve to argpath item (dir or file)
         # and stack all Packages found on the way.
         # No point in finding packages when collecting doctests
-        if not self.config.option.doctestmodules:
+        if not self.config.getoption("doctestmodules", False):
             pm = self.config.pluginmanager
             for parent in reversed(argpath.parts()):
                 if pm._confcutdir and pm._confcutdir.relto(parent):

src/_pytest/runner.py

@@ -87,9 +87,9 @@ def runtestprotocol(item, log=True, nextitem=None):
     rep = call_and_report(item, "setup", log)
     reports = [rep]
     if rep.passed:
-        if item.config.option.setupshow:
+        if item.config.getoption("setupshow", False):
             show_test_item(item)
-        if not item.config.option.setuponly:
+        if not item.config.getoption("setuponly", False):
             reports.append(call_and_report(item, "call", log))
     reports.append(call_and_report(item, "teardown", log, nextitem=nextitem))
     # after all teardown hooks have been called
@@ -192,7 +192,7 @@ def call_runtest_hook(item, when, **kwds):
     hookname = "pytest_runtest_" + when
     ihook = getattr(item.ihook, hookname)
     reraise = (Exit,)
-    if not item.config.getvalue("usepdb"):
+    if not item.config.getoption("usepdb", False):
         reraise += (KeyboardInterrupt,)
     return CallInfo.from_call(
         lambda: ihook(item=item, **kwds), when=when, reraise=reraise

src/_pytest/terminal.py

@@ -251,7 +251,7 @@ class TerminalReporter(object):
         if self.config.getoption("capture", "no") == "no":
             return False
         # do not show progress if we are showing fixture setup/teardown
-        if self.config.getoption("setupshow"):
+        if self.config.getoption("setupshow", False):
             return False
         return self.config.getini("console_output_style") in ("progress", "count")