From f8b944dee0b59bdc483ce505738ea1cb3a57a5b4 Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Wed, 7 Nov 2018 19:33:22 +0100
Subject: [PATCH] pkg_roots

---
 src/_pytest/main.py | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/_pytest/main.py b/src/_pytest/main.py
index a2b27d9fa..59e2b6d4d 100644
--- a/src/_pytest/main.py
+++ b/src/_pytest/main.py
@@ -490,6 +490,7 @@ class Session(nodes.FSCollector):
         names = self._parsearg(arg)
         argpath = names.pop(0).realpath()
         paths = set()
+        pkg_roots = {}
 
         root = self
         # Start with a Session root, and delve to argpath item (dir or file)
@@ -510,9 +511,9 @@ class Session(nodes.FSCollector):
                             col = root._collectfile(pkginit, handle_dupes=False)
                             if col:
                                 if isinstance(col[0], Package):
-                                    root = col[0]
+                                    pkg_roots[parent] = col[0]
                                 # always store a list in the cache, matchnodes expects it
-                                self._node_cache[root.fspath] = [root]
+                                self._node_cache[col[0].fspath] = [col[0]]
 
         # If it's a directory argument, recurse and look for any Subpackages.
         # Let the Package collector deal with subnodes, don't collect here.
@@ -534,16 +535,19 @@ class Session(nodes.FSCollector):
                 fil=filter_, rec=self._recurse, bf=True, sort=True
             ):
                 dirpath = path.dirpath()
+                collect_root = pkg_roots.get(dirpath, root)
                 if dirpath not in seen_dirs:
                     seen_dirs.add(dirpath)
                     pkginit = dirpath.join("__init__.py")
                     if pkginit.exists() and parts(pkginit.strpath).isdisjoint(paths):
-                        for x in root._collectfile(pkginit):
+                        for x in collect_root._collectfile(pkginit):
                             yield x
+                            if isinstance(x, Package):
+                                pkg_roots[dirpath] = x
                             paths.add(x.fspath.dirpath())
 
-                if parts(path.strpath).isdisjoint(paths):
-                    for x in root._collectfile(path):
+                if True or parts(path.strpath).isdisjoint(paths):
+                    for x in collect_root._collectfile(path):
                         key = (type(x), x.fspath)
                         if key in self._node_cache:
                             yield self._node_cache[key]
@@ -556,7 +560,8 @@ class Session(nodes.FSCollector):
             if argpath in self._node_cache:
                 col = self._node_cache[argpath]
             else:
-                col = root._collectfile(argpath)
+                collect_root = pkg_roots.get(argpath.dirname, root)
+                col = collect_root._collectfile(argpath)
                 if col:
                     self._node_cache[argpath] = col
             m = self.matchnodes(col, names)