Deprecate omitting second argument to joinColumnName()

UPGRADE.md

@@ -1,5 +1,46 @@
 # Upgrade to 2.13
 
+## Deprecated omitting second argument to `NamingStrategy::joinColumnName`
+
+When implementing `NamingStrategy`, it is deprecated to implement
+`joinColumnName()` with only one argument.
+
+### Before
+
+```php
+<?php
+class MyStrategy implements NamingStrategy
+{
+    /**
+     * @param string $propertyName A property name.
+     */
+    public function joinColumnName($propertyName): string
+    {
+        // …
+    }
+}
+```
+
+### After
+
+For backward-compatibility reasons, the parameter has to be optional, but can
+be documented as guaranteed to be a `class-string`.
+
+```php
+<?php
+class MyStrategy implements NamingStrategy
+{
+    /**
+     * @param string       $propertyName A property name.
+     * @param class-string $className
+     */
+    public function joinColumnName($propertyName, $className = null): string
+    {
+        // …
+    }
+}
+```
+
 ## Deprecated methods related to named queries
 
 The following methods have been deprecated:

lib/Doctrine/ORM/Mapping/DefaultNamingStrategy.php

@@ -54,6 +54,9 @@ public function referenceColumnName()
 
     /**
      * {@inheritdoc}
+     *
+     * @param string       $propertyName
+     * @param class-string $className
      */
     public function joinColumnName($propertyName, $className = null)
     {

lib/Doctrine/ORM/Mapping/NamingStrategy.php

@@ -56,7 +56,7 @@ public function referenceColumnName();
      *
      * @return string A join column name.
      */
-    public function joinColumnName($propertyName);
+    public function joinColumnName($propertyName/*, $className = null */);
 
     /**
      * Returns a join table name.

lib/Doctrine/ORM/Mapping/UnderscoreNamingStrategy.php

@@ -112,6 +112,9 @@ public function referenceColumnName()
 
     /**
      * {@inheritdoc}
+     *
+     * @param string       $propertyName
+     * @param class-string $className
      */
     public function joinColumnName($propertyName, $className = null)
     {