Fix config order of precedence, putting kernel command line over system.

The correct order of precedence when reading the base config:
  builtin config
  system config
  kernel command line provided config.

This reverts commit 63501f44, which actually broke the behavior it
reported to fix.  It also adds some unit tests to ensure this behavior
is not broken again.

LP: #1582323

2 files changed, 84 insertions, 0 deletions

diff --git a/tests/unittests/helpers.py b/tests/unittests/helpers.py
index a2355a79..a73e3f61 100644
--- a/tests/unittests/helpers.py
+++ b/tests/unittests/helpers.py
@@ -300,6 +300,39 @@ def dir2dict(startdir, prefix=None):
     return flist
 
 
+def wrap_and_call(prefix, mocks, func, *args, **kwargs):
+    """
+    call func(args, **kwargs) with mocks applied, then unapplies mocks
+    nicer to read than repeating dectorators on each function
+
+    prefix: prefix for mock names (e.g. 'cloudinit.stages.util') or None
+    mocks: dictionary of names (under 'prefix') to mock and either
+        a return value or a dictionary to pass to the mock.patch call
+    func: function to call with mocks applied
+    *args,**kwargs: arguments for 'func'
+
+    return_value: return from 'func'
+    """
+    delim = '.'
+    if prefix is None:
+        prefix = ''
+    prefix = prefix.rstrip(delim)
+    unwraps = []
+    for fname, kw in mocks.items():
+        if prefix:
+            fname = delim.join((prefix, fname))
+        if not isinstance(kw, dict):
+            kw = {'return_value': kw}
+        p = mock.patch(fname, **kw)
+        p.start()
+        unwraps.append(p)
+    try:
+        return func(*args, **kwargs)
+    finally:
+        for p in unwraps:
+            p.stop()
+
+
 try:
     skipIf = unittest.skipIf
 except AttributeError:
diff --git a/tests/unittests/test_data.py b/tests/unittests/test_data.py
index 55d9b93f..581b581a 100644
--- a/tests/unittests/test_data.py
+++ b/tests/unittests/test_data.py
@@ -559,3 +559,54 @@ class TestConvertString(helpers.TestCase):
         text = "hi mom"
         msg = ud.convert_string(text)
         self.assertEqual(text, msg.get_payload(decode=False))
+
+
+class TestFetchBaseConfig(helpers.TestCase):
+
+    def test_only_builtin_gets_builtin2(self):
+        ret = helpers.wrap_and_call(
+            'cloudinit.stages.util',
+            {'read_conf_with_confd': None,
+             'read_conf_from_cmdline': None},
+            stages.fetch_base_config)
+        self.assertEqual(util.get_builtin_cfg(), ret)
+
+    def test_conf_d_overrides_defaults(self):
+        builtin = util.get_builtin_cfg()
+        test_key = sorted(builtin)[0]
+        test_value = 'test'
+        ret = helpers.wrap_and_call(
+            'cloudinit.stages.util',
+            {'read_conf_with_confd': {'return_value': {test_key: test_value}},
+             'read_conf_from_cmdline': None},
+            stages.fetch_base_config)
+        self.assertEqual(ret.get(test_key), test_value)
+        builtin[test_key] = test_value
+        self.assertEqual(ret, builtin)
+
+    def test_cmdline_overrides_defaults(self):
+        builtin = util.get_builtin_cfg()
+        test_key = sorted(builtin)[0]
+        test_value = 'test'
+        cmdline = {test_key: test_value}
+        ret = helpers.wrap_and_call(
+            'cloudinit.stages.util',
+            {'read_conf_from_cmdline': {'return_value': cmdline},
+             'read_conf_with_confd': None},
+            stages.fetch_base_config)
+        self.assertEqual(ret.get(test_key), test_value)
+        builtin[test_key] = test_value
+        self.assertEqual(ret, builtin)
+
+    def test_cmdline_overrides_conf_d_and_defaults(self):
+        builtin = {'key1': 'value0', 'key3': 'other2'}
+        conf_d = {'key1': 'value1', 'key2': 'other1'}
+        cmdline = {'key3': 'other3', 'key2': 'other2'}
+        ret = helpers.wrap_and_call(
+            'cloudinit.stages.util',
+            {'read_conf_with_confd': {'return_value': conf_d},
+             'get_builtin_cfg': {'return_value': builtin},
+             'read_conf_from_cmdline': {'return_value': cmdline}},
+            stages.fetch_base_config)
+        self.assertEqual(ret, {'key1': 'value1', 'key2': 'other2',
+                               'key3': 'other3'})