Fix test collection when tests are passed as IDs at the command line. Note this is still broken due to #3358.

_pytest/main.py

@@ -423,9 +423,12 @@ class Session(nodes.FSCollector):
         else:
             assert argpath.check(file=1)
             pkginit = argpath.dirpath().join('__init__.py')
-            if not self.isinitpath(argpath) and pkginit.exists():
+            if not self.isinitpath(pkginit):
+                self._initialpaths.add(pkginit)
+            if pkginit.exists():
                 for x in self._collectfile(pkginit):
-                    yield x
+                    for y in self.matchnodes(x._collectfile(argpath), names):
+                        yield y
             else:
                 for x in self.matchnodes(self._collectfile(argpath), names):
                     yield x

testing/python/collect.py

@@ -927,7 +927,7 @@ def test_setup_only_available_in_subdir(testdir):
 
 
 def test_modulecol_roundtrip(testdir):
-    modcol = testdir.getmodulecol("pass", withinit=True)
+    modcol = testdir.getmodulecol("pass", withinit=False)
     trail = modcol.nodeid
     newcol = modcol.session.perform_collect([trail], genitems=0)[0]
     assert modcol.name == newcol.name

testing/test_collection.py

@@ -587,7 +587,7 @@ class Test_getinitialnodes(object):
         col = testdir.getnode(config, x)
         assert isinstance(col, pytest.Module)
         assert col.name == 'x.py'
-        assert col.parent.parent is None
+        assert col.parent.parent.parent is None
         for col in col.listchain():
             assert col.config is config