Avoid failure if dhcp_end or dhcp_start isn't set

Since dhcp_start and dhcp_end aren't mandatory option, we have to ensure
the validation doesn't fail when they aren't present.

This change introduce a new "default" param to the "ini" module,
allowing to return a success (with the default value) even if the key
isn't found in the file.

Change-Id: Ibd1e54b2d2748b3bf8d2c1cabad3a9faf832e9b2
(cherry picked from commit f84aeec907)

library/ini.py

@@ -53,7 +53,7 @@ def check_file(path, ignore_missing):
         return ''
 
 
-def get_result(path, section, key):
+def get_result(path, section, key, default=None):
     '''Get value based on section and key'''
 
     msg = ''
@@ -74,10 +74,16 @@ def get_result(path, section, key):
         ret = ReturnValue.OK
         return (ret, msg, value)
     except ConfigParser.Error:
-        value = None
-        msg = "There is no key '{}' under the section '{}' in file {}.".format(
-              key, section, path)
-        ret = ReturnValue.KEY_NOT_FOUND
+        if default:
+            msg = ("There is no key '{}' under section '{}' in file {}. Using"
+                   " default value '{}'".format(key, section, path, default))
+            ret = ReturnValue.OK
+            value = default
+        else:
+            value = None
+            msg = "There is no key '{}' under the section '{}' in file {}.".format(
+                  key, section, path)
+            ret = ReturnValue.KEY_NOT_FOUND
         return (ret, msg, value)
 
 
@@ -103,6 +109,10 @@ options:
         description:
             - Section key to look up
         type: str
+    default:
+        required: false
+        description:
+            - Default value if key isn't found
     ignore_missing_file:
         required: false
         description:
@@ -140,8 +150,9 @@ def main():
         # Try to parse the result from ini file
         section = module.params.get('section')
         key = module.params.get('key')
+        default = module.params.get('default')
 
-        ret, msg, value = get_result(ini_file_path, section, key)
+        ret, msg, value = get_result(ini_file_path, section, key, default)
 
         if ret == ReturnValue.INVALID_FORMAT:
             module.fail_json(msg=msg)

roles/ctlplane-ip-range/tasks/main.yml

@@ -11,6 +11,7 @@
     section: ctlplane-subnet
     key: dhcp_start
     ignore_missing_file: True
+    default: "192.0.2.5"
   register: dhcp_start
 
 - name: Get dhcp_end value from the undercloud.conf file
@@ -20,10 +21,11 @@
     section: ctlplane-subnet
     key: dhcp_end
     ignore_missing_file: True
+    default: "192.0.2.24"
   register: dhcp_end
 
 - name: Check the size of the DHCP range for overcloud nodes
   ip_range:
-    start: "{{ dhcp_start.value|default('192.0.2.5', true) }}"
-    end: "{{ dhcp_end.value|default('192.0.2.24', true) }}"
+    start: "{{ dhcp_start.value }}"
+    end: "{{ dhcp_end.value }}"
     min_size: "{{ ctlplane_iprange_min_size }}"

tripleo_validations/tests/library/test_ini.py

@@ -101,6 +101,23 @@ class TestIni(base.TestCase):
                           "in file {}.").format(tmp_name), msg)
         self.assertIsNone(value)
 
+    def test_get_result_key_not_found_with_default(self):
+        '''Test ini when key is not found but has a default'''
+
+        tmpfile = self.create_tmp_ini()
+        tmp_name = os.path.relpath(tmpfile.name)
+        tmpfile.write(valid_content.encode('utf-8'))
+        tmpfile.seek(0)
+        ret, msg, value = validation.get_result(tmp_name, 'section', 'key',
+                                                'foo')
+        tmpfile.close()
+
+        self.assertEqual(validation.ReturnValue.OK, ret)
+        self.assertEqual(("There is no key 'key' under section 'section' "
+                          "in file {}. Using default value '{}'"
+                          ).format(tmp_name, 'foo'), msg)
+        self.assertEqual(value, 'foo')
+
     def test_get_result_ok(self):
         '''Test ini when key is not found'''