Deprecate overwriting existing FK constraints

Overwriting an existing foreign key constraint is now deprecated
This behavior will no longer be allowed in Doctrine DBAL 5.0, where
an exception will be thrown instead of silently overwriting the
constraint.

Author: santysisi

UPGRADE.md

@@ -8,6 +8,12 @@ awareness about deprecated code.
 
 # Upgrade to 4.4
 
+## Deprecated overwriting foreign key constraints
+
+Adding a foreign key constraint with a name that matches an existing one, whether explicitly specified or
+auto-generated, has been deprecated. In order to replace an existing constraint, drop it first
+via `dropForeignKey()`.
+
 ## Deprecated `View` features
 
 The `View` constructor has been marked as internal. Use `View::editor()` to instantiate an editor and

src/Schema/Table.php

@@ -938,6 +938,14 @@ protected function _addForeignKeyConstraint(ForeignKeyConstraint $constraint): s
             );
 
         $name = $this->normalizeIdentifier($name);
+        if (isset($this->_fkConstraints[$name])) {
+            Deprecation::trigger(
+                'doctrine/dbal',
+                'https://github.com/doctrine/dbal/pull/7125',
+                'Overwriting an existing foreign key constraint ("%s") is deprecated.',
+                $name,
+            );
+        }
 
         $this->_fkConstraints[$name] = $constraint;
 

tests/Schema/TableTest.php

@@ -1768,4 +1768,22 @@ public function testInvalidPrimaryKeyIndex(): void
         $this->expectException(InvalidState::class);
         $table->getPrimaryKeyConstraint();
     }
+
+    public function testOverwritingForeignKeyConstraint(): void
+    {
+        $table = Table::editor()
+            ->setUnquotedName('foo')
+            ->setColumns(
+                Column::editor()
+                    ->setUnquotedName('id')
+                    ->setTypeName(Types::INTEGER)
+                    ->create(),
+            )
+            ->create();
+
+        $table->addForeignKeyConstraint('bar', ['id'], ['id']);
+
+        $this->expectDeprecationWithIdentifier('https://github.com/doctrine/dbal/pull/7125');
+        $table->addForeignKeyConstraint('baz', ['id'], ['id']);
+    }
 }