Repository: Allow to check for conversion rules of a specific column

library/Icinga/Repository/DbRepository.php

@@ -463,17 +463,33 @@ abstract class DbRepository extends Repository implements Extensible, Updatable,
     }
 
     /**
-     * Return whether this repository is capable of converting values
+     * Return whether this repository is capable of converting values for the given table and optional column
      *
-     * This does not check whether any conversion for the given table is available, as it may be possible
-     * that columns from another table where joined in which would otherwise not being converted.
+     * This does not check whether any conversion for the given table is available if $column is not given, as it
+     * may be possible that columns from another table where joined in which would otherwise not being converted.
      *
      * @param   array|string    $table
+     * @param   string          $column
      *
      * @return  bool
      */
-    public function providesValueConversion($_)
+    public function providesValueConversion($table, $column = null)
     {
+        if ($column !== null) {
+            if ($this->validateQueryColumnAssociation($table, $column)) {
+                return parent::providesValueConversion(
+                    $this->removeTablePrefix($this->clearTableAlias($table)),
+                    $column
+                );
+            }
+
+            if (($tableName = $this->findTableName($column))) {
+                return parent::providesValueConversion($tableName, $column);
+            }
+
+            return false;
+        }
+
         $conversionRules = $this->getConversionRules();
         return !empty($conversionRules);
     }

library/Icinga/Repository/Repository.php

@@ -464,16 +464,28 @@ abstract class Repository implements Selectable
     }
 
     /**
-     * Return whether this repository is capable of converting values for the given table
+     * Return whether this repository is capable of converting values for the given table and optional column
      *
      * @param   string  $table
+     * @param   string  $column
      *
      * @return  bool
      */
-    public function providesValueConversion($table)
+    public function providesValueConversion($table, $column = null)
     {
         $conversionRules = $this->getConversionRules();
-        return !empty($conversionRules) && isset($conversionRules[$table]);
+        if (empty($conversionRules)) {
+            return false;
+        }
+
+        if (! isset($conversionRules[$table])) {
+            return false;
+        } elseif ($column === null) {
+            return true;
+        }
+
+        $alias = $this->reassembleQueryColumnAlias($table, $column) ?: $column;
+        return array_key_exists($alias, $conversionRules[$table]) || in_array($alias, $conversionRules[$table]);
     }
 
     /**