fix issue #2920

AUTHORS

@@ -186,3 +186,4 @@ Wouter van Ackooy
 Xuan Luong
 Xuecong Liao
 Zoltán Máté
+Roland Puntaier

_pytest/config.py

@@ -417,7 +417,7 @@ def import_plugin(self, modname):
         # _pytest prefix.
         assert isinstance(modname, (six.text_type, str)), "module name as text required, got %r" % modname
         modname = str(modname)
-        if self.get_plugin(modname) is not None:
+        if self.is_blocked(modname) or self.get_plugin(modname) is not None:
             return
         if modname in builtin_plugins:
             importspec = "_pytest." + modname

changelog/2920.bugfix

@@ -0,0 +1 @@
+Fix issue about ``-p no:<plugin>`` having no effect.

changelog/2949.trivial

@@ -1 +1 @@
-iUpdate github "bugs" link in CONTRIBUTING.rst
+Update github "bugs" link in CONTRIBUTING.rst

testing/test_config.py

@@ -1,4 +1,5 @@
 from __future__ import absolute_import, division, print_function
+import sys
 import py
 import pytest
 
@@ -459,9 +460,12 @@ def load(self):
         testdir.parseconfig()
 
 
-def test_plugin_preparse_prevents_setuptools_loading(testdir, monkeypatch):
+@pytest.mark.parametrize('block_it', [True, False])
+def test_plugin_preparse_prevents_setuptools_loading(testdir, monkeypatch, block_it):
     pkg_resources = pytest.importorskip("pkg_resources")
 
+    plugin_module_placeholder = object()
+
     def my_iter(name):
         assert name == "pytest11"
 
@@ -477,14 +481,19 @@ class EntryPoint(object):
             dist = Dist()
 
             def load(self):
-                assert 0, "should not arrive here"
+                return plugin_module_placeholder
 
         return iter([EntryPoint()])
 
     monkeypatch.setattr(pkg_resources, 'iter_entry_points', my_iter)
-    config = testdir.parseconfig("-p", "no:mytestplugin")
-    plugin = config.pluginmanager.getplugin("mytestplugin")
-    assert plugin is None
+    args = ("-p", "no:mytestplugin") if block_it else ()
+    config = testdir.parseconfig(*args)
+    config.pluginmanager.import_plugin("mytestplugin")
+    if block_it:
+        assert "mytestplugin" not in sys.modules
+        assert config.pluginmanager.get_plugin('mytestplugin') is None
+    else:
+        assert config.pluginmanager.get_plugin('mytestplugin') is plugin_module_placeholder
 
 
 def test_cmdline_processargs_simple(testdir):