Support nested keys expressed as single strings in the PreservingIniWriter

Automatically convert keys with dots into nested configurations to avoid errors during the property diff, of the old and new configuration file.

library/Icinga/Config/PreservingIniWriter.php

@@ -38,6 +38,45 @@ class PreservingIniWriter extends Zend_Config_Writer_FileAbstract
         parent::__construct($options);
     }
 
+    /**
+     * Find all keys containing dots and convert it to a nested configuration
+     *
+     * Ensure that configurations with the same ini representation the have
+     * similarly nested Zend_Config objects. The configuration may be altered
+     * during that process.
+     *
+     * @param   Zend_Config $config   The configuration to normalize
+     * @return  Zend_Config           The normalized config
+     */
+    private function normalizeKeys(Zend_Config $config)
+    {
+        foreach ($config as $key => $value) {
+            if (preg_match('/\./', $key) > 0) {
+                // remove old key
+                unset ($config->$key);
+
+                // insert new key
+                $nests = explode('.', $key);
+                $current = $config;
+                $i = 0;
+                for (; $i < count($nests) - 1; $i++) {
+                    if (! isset($current->{$nests[$i]})) {
+                        // configuration key doesn't exist, create a new nesting level
+                        $current->{$nests[$i]} = new Zend_Config (array(), true);
+                    }
+                    // move to next nesting level
+                    $current = $current->{$nests[$i]};
+                }
+                // reached last nesting level, insert value
+                $current->{$nests[$i]} = $value;
+            }
+            if ($value instanceof Zend_Config) {
+                $config->$key = $this->normalizeKeys ($value);
+            }
+        }
+        return $config;
+    }
+
     /**
      * Render the Zend_Config into a config file string
      *
@@ -50,6 +89,17 @@ class PreservingIniWriter extends Zend_Config_Writer_FileAbstract
         } else {
             $oldconfig = new Zend_Config(array());
         }
+
+        // create an internal copy of the given configuration, since the user of this class
+        // won't expect that a configuration will ever be altered during
+        // the rendering process.
+        $extends = $this->_config->getExtends();
+        $this->_config = new Zend_Config ($this->_config->toArray(), true);
+        foreach ($extends as $extending => $extended) {
+           $this->_config->setExtend($extending, $extended);
+        }
+        $this->_config = $this->normalizeKeys($this->_config);
+
         $newconfig = $this->_config;
         $editor = new IniEditor(file_get_contents($this->_filename), $this->options);
         $this->diffConfigs($oldconfig, $newconfig, $editor);