Root is acceptable as a combining path (the manylinux tests end up with one of these)

1 files changed, 10 insertions, 2 deletions

diff --git a/coverage/files.py b/coverage/files.py
index 346043d..04ce9cb 100644
--- a/coverage/files.py
+++ b/coverage/files.py
@@ -302,6 +302,11 @@ class PathAliases(object):
     def __init__(self):
         self.aliases = []
 
+    def pprint(self):       # pragma: debugging
+        """Dump the important parts of the PathAliases, for debugging."""
+        for regex, result, _, _ in self.aliases:
+            print("{0!r} --> {1!r}".format(regex.pattern, result))
+
     def add(self, pattern, result):
         """Add the `pattern`/`result` pair to the list of aliases.
 
@@ -315,8 +320,10 @@ class PathAliases(object):
         match an entire tree, and not just its root.
 
         """
+        if len(pattern) > 1:
+            pattern = pattern.rstrip(r"\/")
+
         # The pattern can't end with a wildcard component.
-        pattern = pattern.rstrip(r"\/")
         if pattern.endswith("*"):
             raise CoverageException("Pattern must not end with wildcards.")
         pattern_sep = sep(pattern)
@@ -325,7 +332,8 @@ class PathAliases(object):
         # unless it already is, or is meant to match any prefix.
         if not pattern.startswith('*') and not isabs_anywhere(pattern):
             pattern = abs_file(pattern)
-        pattern += pattern_sep
+        if not pattern.endswith(pattern_sep):
+            pattern += pattern_sep
 
         # Make a regex from the pattern.  fnmatch always adds a \Z to
         # match the whole string, which we don't want, so we remove the \Z.