Fix --append trying to make a new file. #392

1 files changed, 6 insertions, 3 deletions

diff --git a/coverage/cmdline.py b/coverage/cmdline.py
index 0a84aa1..b2ffdf7 100644
--- a/coverage/cmdline.py
+++ b/coverage/cmdline.py
@@ -5,6 +5,7 @@
 
 import glob
 import optparse
+import os.path
 import sys
 import traceback
 
@@ -344,7 +345,7 @@ class CoverageScript(object):
     """The command-line interface to coverage.py."""
 
     def __init__(self, _covpkg=None, _run_python_file=None,
-                 _run_python_module=None, _help_fn=None):
+                 _run_python_module=None, _help_fn=None, _path_exists=None):
         # _covpkg is for dependency injection, so we can test this code.
         if _covpkg:
             self.covpkg = _covpkg
@@ -356,6 +357,7 @@ class CoverageScript(object):
         self.run_python_file = _run_python_file or run_python_file
         self.run_python_module = _run_python_module or run_python_module
         self.help_fn = _help_fn or self.help
+        self.path_exists = _path_exists or os.path.exists
         self.global_option = False
 
         self.coverage = None
@@ -575,8 +577,9 @@ class CoverageScript(object):
             self.coverage.stop()
             if code_ran:
                 if options.append:
-                    data_paths = [self.coverage.get_option("run:data_file")]
-                    self.coverage.combine(data_paths=data_paths)
+                    data_file = self.coverage.get_option("run:data_file")
+                    if self.path_exists(data_file):
+                        self.coverage.combine(data_paths=[data_file])
                 self.coverage.save()
 
         return OK