Ensure _run_shell_command always returns same type

If _run_shell_command gets no output, return an empty
string instead of None. This ensures that callers can
always treat the results as a string, and avoids the
TypeError that was preventing the ChangeLog and AUTHORS
files from being created properly in a git repository
without any commits.

Change-Id: I880210bc3ff92ece29b216a10e1d0c918f884eaf

2 files changed, 107 insertions, 1 deletions

diff --git a/pbr/packaging.py b/pbr/packaging.py
index 8e6ab4a..366f21e 100644
--- a/pbr/packaging.py
+++ b/pbr/packaging.py
@@ -220,7 +220,7 @@ def _run_shell_command(cmd, throw_on_error=False, buffer=True):
         raise distutils.errors.DistutilsError(
             "%s returned %d" % (cmd, output.returncode))
     if len(out) == 0 or not out[0] or not out[0].strip():
-        return None
+        return ''
     return out[0].strip().decode('utf-8')
 
 
diff --git a/pbr/tests/test_packaging.py b/pbr/tests/test_packaging.py
new file mode 100644
index 0000000..7461c0f
--- /dev/null
+++ b/pbr/tests/test_packaging.py
@@ -0,0 +1,106 @@
+# Copyright (c) 2013 New Dream Network, LLC (DreamHost)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Copyright (C) 2013 Association of Universities for Research in Astronomy
+#                    (AURA)
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#     1. Redistributions of source code must retain the above copyright
+#        notice, this list of conditions and the following disclaimer.
+#
+#     2. Redistributions in binary form must reproduce the above
+#        copyright notice, this list of conditions and the following
+#        disclaimer in the documentation and/or other materials provided
+#        with the distribution.
+#
+#     3. The name of AURA and its representatives may not be used to
+#        endorse or promote products derived from this software without
+#        specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY AURA ``AS IS'' AND ANY EXPRESS OR IMPLIED
+# WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL AURA BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+
+import os
+
+from pbr import tests
+
+
+class TestPackagingInGitRepoWithCommit(tests.BaseTestCase):
+
+    def setUp(self):
+        super(TestPackagingInGitRepoWithCommit, self).setUp()
+        self._run_cmd('git', ['init', '.'])
+        self._run_cmd('git', ['add', '.'])
+        self._run_cmd('git', ['commit', '-m', 'test commit'])
+        self.run_setup('sdist')
+        return
+
+    def test_authors(self):
+        # One commit, something should be in the authors list
+        with open(os.path.join(self.package_dir, 'AUTHORS'), 'r') as f:
+            body = f.read()
+        self.assertNotEqual(body, '')
+
+    def test_changelog(self):
+        with open(os.path.join(self.package_dir, 'ChangeLog'), 'r') as f:
+            body = f.read()
+        # One commit, something should be in the ChangeLog list
+        self.assertNotEqual(body, '')
+
+
+class TestPackagingInGitRepoWithoutCommit(tests.BaseTestCase):
+
+    def setUp(self):
+        super(TestPackagingInGitRepoWithoutCommit, self).setUp()
+        self._run_cmd('git', ['init', '.'])
+        self._run_cmd('git', ['add', '.'])
+        self.run_setup('sdist')
+        return
+
+    def test_authors(self):
+        # No commits, no authors in list
+        with open(os.path.join(self.package_dir, 'AUTHORS'), 'r') as f:
+            body = f.read()
+        self.assertEqual(body, '')
+
+    def test_changelog(self):
+        # No commits, nothing should be in the ChangeLog list
+        with open(os.path.join(self.package_dir, 'ChangeLog'), 'r') as f:
+            body = f.read()
+        self.assertEqual(body, '')
+
+
+class TestPackagingInPlainDirectory(tests.BaseTestCase):
+
+    def setUp(self):
+        super(TestPackagingInPlainDirectory, self).setUp()
+        self.run_setup('sdist')
+        return
+
+    def test_authors(self):
+        # Not a git repo, no AUTHORS file created
+        filename = os.path.join(self.package_dir, 'AUTHORS')
+        self.assertFalse(os.path.exists(filename))
+
+    def test_changelog(self):
+        # Not a git repo, no ChangeLog created
+        filename = os.path.join(self.package_dir, 'ChangeLog')
+        self.assertFalse(os.path.exists(filename))