allow modules/conftest files specify dotted import paths for loading plugins

doc/customize.txt

@@ -128,15 +128,19 @@ py.test loads plugin modules at tool startup in the following way:
 * by recursively loading all plugins specified by the
   ``pytest_plugins`` variable in ``conftest.py`` files
 
-Requiring/Loading plugins in a test module or plugin
+Requiring/Loading plugins in a test module or conftest file
 -------------------------------------------------------------
 
-You can require plugins in a test module or a plugin like this::
+You can require plugins in a test module or a conftest file like this::
 
     pytest_plugins = "name1", "name2",
 
-When the test module or plugin is loaded the specified plugins
-will be loaded.
+When the test module or conftest plugin is loaded the specified plugins
+will be loaded as well.  You can also use dotted path like this::
+
+    pytest_plugins = "myapp.testsupport.myplugin"
+
+which will import the specified module as a py.test plugin.
 
 .. _`setuptools entry points`:
 .. _registered:

pytest/_core.py

@@ -218,15 +218,16 @@ class PluginManager(object):
                 kwargs=kwargs, firstresult=True).execute()
 
 def canonical_importname(name):
+    if '.' in name:
+        return name
     name = name.lower()
     if not name.startswith(IMPORTPREFIX):
         name = IMPORTPREFIX + name
     return name
 
 def importplugin(importspec):
-    #print "importing", importspec
     try:
-        return __import__(importspec)
+        return __import__(importspec, None, None, '__doc__')
     except ImportError:
         e = py.std.sys.exc_info()[1]
         if str(e).find(importspec) == -1:
@@ -241,7 +242,7 @@ def importplugin(importspec):
             if str(e).find(name) == -1:
                 raise
             # show the original exception, not the failing internal one
-            return __import__(importspec)
+            return __import__(importspec, None, None, '__doc__')
 
 
 class MultiCall:

testing/test_pluginmanager.py

@@ -101,6 +101,18 @@ class TestBootstrapping:
         plugin2 = pluginmanager.getplugin("hello")
         assert plugin2 is plugin1
 
+    def test_import_plugin_dotted_name(self, testdir):
+        pluginmanager = PluginManager()
+        py.test.raises(ImportError, 'pluginmanager.import_plugin("x.y")')
+        py.test.raises(ImportError, 'pluginmanager.import_plugin("pytest_x.y")')
+
+        reset = testdir.syspathinsert()
+        testdir.mkpydir("pkg").join("plug.py").write("x=3")
+        pluginname = "pkg.plug"
+        pluginmanager.import_plugin(pluginname)
+        mod = pluginmanager.getplugin("pkg.plug")
+        assert mod.x == 3
+
     def test_consider_module(self, testdir):
         pluginmanager = PluginManager()
         testdir.syspathinsert()