Fixed pytest-dev#2148 - parse directory names properly when args contains ::.

This commit also improves readbility in get_dirs_from_args by using self
documenting local functions.

get_dirs_from_args also now only returns directories that actually exists,
and not files to avoid confusion.

This commit also removes redundant checks in get_common_ancestor that
was already performed in get_dirs_from_args..

Author: pelme

CHANGELOG.rst

@@ -9,13 +9,17 @@
   expected warnings and the list of caught warnings is added to the
   error message. Thanks `@lesteve`_ for the PR.
 
-*
+* Specifying tests with colons like ``test_foo.py::test_bar`` for tests in
+  subdirectories with ini configuration files now uses the correct ini file
+  (`#2148`_).  Thanks `@pelme`.
 
 *
 
 .. _@lesteve: https://github.com/lesteve
+.. _@pelme: https://github.com/pelme
 
 .. _#2150: https://github.com/pytest-dev/pytest/issues/2150
+.. _#2148: https://github.com/pytest-dev/pytest/issues/2148
 
 
 3.0.5 (2016-12-05)

_pytest/config.py

@@ -1228,25 +1228,22 @@ def getcfg(args, warnfunc=None):
     return None, None, None
 
 
-def get_common_ancestor(args):
+def get_common_ancestor(paths):
     # args are what we get after early command line parsing (usually
     # strings, but can be py.path.local objects as well)
     common_ancestor = None
-    for arg in args:
-        if str(arg)[0] == "-":
-            continue
-        p = py.path.local(arg)
-        if not p.exists():
+    for path in paths:
+        if not path.exists():
             continue
         if common_ancestor is None:
-            common_ancestor = p
+            common_ancestor = path
         else:
-            if p.relto(common_ancestor) or p == common_ancestor:
+            if path.relto(common_ancestor) or path == common_ancestor:
                 continue
-            elif common_ancestor.relto(p):
-                common_ancestor = p
+            elif common_ancestor.relto(path):
+                common_ancestor = path
             else:
-                shared = p.common(common_ancestor)
+                shared = path.common(common_ancestor)
                 if shared is not None:
                     common_ancestor = shared
     if common_ancestor is None:
@@ -1257,9 +1254,29 @@ def get_common_ancestor(args):
 
 
 def get_dirs_from_args(args):
-    return [d for d in (py.path.local(x) for x in args
-                        if not str(x).startswith("-"))
-            if d.exists()]
+    def is_option(x):
+        return str(x).startswith('-')
+
+    def get_file_part_from_node_id(x):
+        return str(x).split('::')[0]
+
+    def get_dir_from_path(path):
+        if path.isdir():
+            return path
+        return py.path.local(path.dirname)
+
+    # These looks like paths but may not exist
+    possible_paths = (
+        py.path.local(get_file_part_from_node_id(arg))
+        for arg in args
+        if not is_option(arg)
+    )
+
+    return [
+        get_dir_from_path(path)
+        for path in possible_paths
+        if path.exists()
+    ]
 
 
 def determine_setup(inifile, args, warnfunc=None):