if source looks like a package add it to source_pkgs

coverage/inorout.py

@@ -7,10 +7,12 @@
 import atexit
 import inspect
 import itertools
+import keyword
 import os
 import platform
 import re
 import sys
+import tokenize
 import traceback
 
 from coverage import env
@@ -108,6 +110,14 @@ def module_has_file(mod):
     return os.path.exists(mod__file__)
 
 
+_IS_PKG_RE = re.compile(
+    r"\A(((?!keywords){tokenize.Name})\.?)+\Z".format(
+        tokenize=tokenize,
+        keywords="|".join(re.escape(kw) for kw in keyword.kwlist),
+    )
+)
+
+
 class InOrOut(object):
     """Machinery for determining what files to measure."""
 
@@ -133,10 +143,11 @@ def __init__(self, warn, debug):
     def configure(self, config):
         """Apply the configuration to get ready for decision-time."""
         for src in config.source or []:
+            if _IS_PKG_RE.match(src):
+                self.source_pkgs.append(src)
             if os.path.isdir(src):
                 self.source.append(canonical_filename(src))
-            else:
-                self.source_pkgs.append(src)
+
         self.source_pkgs_unmatched = self.source_pkgs[:]
 
         self.omit = prep_patterns(config.run_omit)