Add missing config file read to tempest init

The update_local_conf() portion of tempest init was never reading the
config file. In the case we prepopulate a tempest.conf from the global
state /etc dir this would result in tempest init duplicating options
and sections that already existed. This commit fixes the issue by
simply reading the file before we do any operations.

Also add test coverage to ensure existing settings are not overwritten.

Co-authored-by: Augustina Ragwitz <auggy@cpan.org>
Change-Id: Ie629df246fc40777f2017b78e4073ae833b64deb

tempest/cmd/init.py

@@ -89,18 +89,28 @@ class TempestInit(command.Command):
         with open(testr_conf_path, 'w+') as testr_conf_file:
             testr_conf_file.write(testr_conf)
 
-    def update_local_conf(self, conf_path, lock_dir, log_dir):
+    def get_configparser(self, conf_path):
         config_parse = moves.configparser.SafeConfigParser()
         config_parse.optionxform = str
-        with open(conf_path, 'a+') as conf_file:
-            # Set local lock_dir in tempest conf
-            if not config_parse.has_section('oslo_concurrency'):
-                config_parse.add_section('oslo_concurrency')
-            config_parse.set('oslo_concurrency', 'lock_path', lock_dir)
-            # Set local log_dir in tempest conf
-            config_parse.set('DEFAULT', 'log_dir', log_dir)
-            # Set default log filename to tempest.log
-            config_parse.set('DEFAULT', 'log_file', 'tempest.log')
+        # get any existing values if a config file already exists
+        if os.path.isfile(conf_path):
+            # use read() for Python 2 and 3 compatibility
+            config_parse.read(conf_path)
+        return config_parse
+
+    def update_local_conf(self, conf_path, lock_dir, log_dir):
+        config_parse = self.get_configparser(conf_path)
+        # Set local lock_dir in tempest conf
+        if not config_parse.has_section('oslo_concurrency'):
+            config_parse.add_section('oslo_concurrency')
+        config_parse.set('oslo_concurrency', 'lock_path', lock_dir)
+        # Set local log_dir in tempest conf
+        config_parse.set('DEFAULT', 'log_dir', log_dir)
+        # Set default log filename to tempest.log
+        config_parse.set('DEFAULT', 'log_file', 'tempest.log')
+
+        # write out a new file with the updated configurations
+        with open(conf_path, 'w+') as conf_file:
             config_parse.write(conf_file)
 
     def copy_config(self, etc_dir, config_dir):

tempest/tests/cmd/test_tempest_init.py

@@ -45,6 +45,7 @@ class TestTempestInit(base.TestCase):
         init_cmd = init.TempestInit(None, None)
         local_sample_conf_file = os.path.join(etc_dir_path,
                                               'tempest.conf.sample')
+
         # Verify no sample config file exist
         self.assertFalse(os.path.isfile(local_sample_conf_file))
         init_cmd.generate_sample_config(local_dir.path)
@@ -53,6 +54,52 @@ class TestTempestInit(base.TestCase):
         self.assertTrue(os.path.isfile(local_sample_conf_file))
         self.assertGreater(os.path.getsize(local_sample_conf_file), 0)
 
+    def test_update_local_conf(self):
+        local_dir = self.useFixture(fixtures.TempDir())
+        etc_dir_path = os.path.join(local_dir.path, 'etc/')
+        os.mkdir(etc_dir_path)
+        lock_dir = os.path.join(local_dir.path, 'tempest_lock')
+        config_path = os.path.join(etc_dir_path, 'tempest.conf')
+        log_dir = os.path.join(local_dir.path, 'logs')
+
+        init_cmd = init.TempestInit(None, None)
+
+        # Generate the config file
+        init_cmd.generate_sample_config(local_dir.path)
+
+        # Create a conf file with populated values
+        config_parser_pre = init_cmd.get_configparser(config_path)
+        with open(config_path, 'w+') as conf_file:
+            # create the same section init will check for and add values to
+            config_parser_pre.add_section('oslo_concurrency')
+            config_parser_pre.set('oslo_concurrency', 'TEST', local_dir.path)
+            # create a new section
+            config_parser_pre.add_section('TEST')
+            config_parser_pre.set('TEST', 'foo', "bar")
+            config_parser_pre.write(conf_file)
+
+        # Update the config file the same way tempest init does
+        init_cmd.update_local_conf(config_path, lock_dir, log_dir)
+
+        # parse the new config file to verify it
+        config_parser_post = init_cmd.get_configparser(config_path)
+
+        # check that our value in oslo_concurrency wasn't overwritten
+        self.assertTrue(config_parser_post.has_section('oslo_concurrency'))
+        self.assertEqual(config_parser_post.get('oslo_concurrency', 'TEST'),
+                         local_dir.path)
+        # check that the lock directory was set correctly
+        self.assertEqual(config_parser_post.get('oslo_concurrency',
+                                                'lock_path'), lock_dir)
+
+        # check that our new section still exists and wasn't modified
+        self.assertTrue(config_parser_post.has_section('TEST'))
+        self.assertEqual(config_parser_post.get('TEST', 'foo'), 'bar')
+
+        # check that the DEFAULT values are correct
+        # NOTE(auggy): has_section ignores DEFAULT
+        self.assertEqual(config_parser_post.get('DEFAULT', 'log_dir'), log_dir)
+
     def test_create_working_dir_with_existing_local_dir_non_empty(self):
         fake_local_dir = self.useFixture(fixtures.TempDir())
         fake_local_conf_dir = self.useFixture(fixtures.TempDir())