Fix duplicate foreign key deprecation with Single Table Inheritance

When multiple STI child entities have a ManyToOne relation to the same
target entity using the same join column, SchemaTool called
addForeignKeyConstraint twice with the same constraint name, triggering
a DBAL deprecation ("Overwriting an existing foreign key constraint").

The fix skips the redundant addForeignKeyConstraint call when an
identical FK (same local columns, same foreign table, same foreign
columns) was already added.

See doctrine/dbal#7125

Author: janedbal

src/Tools/SchemaTool.php

@@ -834,7 +834,7 @@ class_exists(ForeignKeyConstraintEditor::class)
             }
 
             $blacklistedFks[$compositeName] = true;
-        } elseif (! isset($blacklistedFks[$compositeName])) {
+        } elseif (! isset($blacklistedFks[$compositeName]) && ! isset($addedFks[$compositeName])) {
             $addedFks[$compositeName] = ['foreignTableName' => $foreignTableName, 'foreignColumns' => $foreignColumns];
             $theJoinTable->addForeignKeyConstraint(
                 $foreignTableName,

tests/Tests/ORM/Tools/SchemaToolTest.php

@@ -17,9 +17,13 @@
 use Doctrine\DBAL\Types\Types;
 use Doctrine\ORM\Mapping\ClassMetadata;
 use Doctrine\ORM\Mapping\Column;
+use Doctrine\ORM\Mapping\DiscriminatorColumn;
+use Doctrine\ORM\Mapping\DiscriminatorMap;
 use Doctrine\ORM\Mapping\Entity;
+use Doctrine\ORM\Mapping\GeneratedValue;
 use Doctrine\ORM\Mapping\Id;
 use Doctrine\ORM\Mapping\Index;
+use Doctrine\ORM\Mapping\InheritanceType;
 use Doctrine\ORM\Mapping\JoinColumn;
 use Doctrine\ORM\Mapping\ManyToOne;
 use Doctrine\ORM\Mapping\MappingException;
@@ -523,6 +527,39 @@ private static function columnIsIndexed(DbalTable $table, string $column): bool
 
         return false;
     }
+
+    public function testSingleTableInheritanceWithSameForeignKeyInChildrenDoesNotTriggerDeprecation(): void
+    {
+        $em         = $this->getTestEntityManager();
+        $schemaTool = new SchemaTool($em);
+
+        $schema = $schemaTool->getSchemaFromMetadata([
+            $em->getClassMetadata(STIBox::class),
+            $em->getClassMetadata(STILocation::class),
+            $em->getClassMetadata(STIBoxContainer::class),
+            $em->getClassMetadata(STIPackedBoxContainer::class),
+        ]);
+
+        self::assertTrue($schema->hasTable('sti_location'));
+
+        $table = $schema->getTable('sti_location');
+
+        self::assertCount(1, $table->getForeignKeys());
+
+        $foreignKeys = $table->getForeignKeys();
+        $foreignKey  = current($foreignKeys);
+
+        if (class_exists(ForeignKeyConstraintEditor::class)) {
+            self::assertSame('sti_box', $foreignKey->getReferencedTableName()->toString());
+            self::assertSame(['box_id'], array_map(
+                static fn (UnqualifiedName $name) => $name->toString(),
+                $foreignKey->getReferencingColumnNames(),
+            ));
+        } else {
+            self::assertSame('sti_box', $foreignKey->getForeignTableName());
+            self::assertSame(['box_id'], $foreignKey->getLocalColumns());
+        }
+    }
 }
 
 #[Table(options: ['foo' => 'bar', 'baz' => ['key' => 'val']])]
@@ -758,3 +795,42 @@ class QuotedEntity
     #[Column(name: '`quoted-name`')]
     public string $name = '';
 }
+
+#[Entity]
+#[Table(name: 'sti_box')]
+class STIBox
+{
+    #[Id]
+    #[Column(type: 'integer')]
+    #[GeneratedValue]
+    public int|null $id = null;
+}
+
+#[Entity]
+#[Table(name: 'sti_location')]
+#[InheritanceType('SINGLE_TABLE')]
+#[DiscriminatorColumn(name: 'type', type: 'string')]
+#[DiscriminatorMap(['box_container' => STIBoxContainer::class, 'packed_box_container' => STIPackedBoxContainer::class])]
+abstract class STILocation
+{
+    #[Id]
+    #[Column(type: 'integer')]
+    #[GeneratedValue]
+    public int|null $id = null;
+}
+
+#[Entity]
+class STIBoxContainer extends STILocation
+{
+    #[ManyToOne(targetEntity: STIBox::class)]
+    #[JoinColumn(name: 'box_id', referencedColumnName: 'id')]
+    public STIBox|null $box = null;
+}
+
+#[Entity]
+class STIPackedBoxContainer extends STILocation
+{
+    #[ManyToOne(targetEntity: STIBox::class)]
+    #[JoinColumn(name: 'box_id', referencedColumnName: 'id')]
+    public STIBox|null $box = null;
+}