Fix: #6146 - utf8/utf8mb3 alias causes redundant ALTER TABLE changes

src/Platforms/AbstractMySQLPlatform.php

@@ -856,4 +856,14 @@
 
         return $sql . ' WHERE ' . implode(' AND ', $conditions);
     }
+
+    /**
+     * INFORMATION_SCHEMA.CHARACTER_SETS will contain either 'utf8' or 'utf8mb3' but not both.
+     */
+    public function informationSchemaUsesUtf8mb3(Connection $connection): bool
+    {
+        $sql = "SELECT character_set_name FROM INFORMATION_SCHEMA.CHARACTER_SETS WHERE character_set_name = 'utf8mb3'";
+
+        return $connection->fetchOne($sql) === 'utf8mb3';
+    }
 }

src/Platforms/MySQL/CharsetMetadataProvider.php

@@ -7,5 +7,7 @@
 /** @internal */
 interface CharsetMetadataProvider
 {
+    public function normalizeCharset(string $charset): string;
+
     public function getDefaultCharsetCollation(string $charset): ?string;
 }

src/Platforms/MySQL/CharsetMetadataProvider/CachingCharsetMetadataProvider.php

@@ -18,6 +18,11 @@
     {
     }
 
+    public function normalizeCharset(string $charset): string
+    {
+        return $this->charsetMetadataProvider->normalizeCharset($charset);
+    }
+
     public function getDefaultCharsetCollation(string $charset): ?string
     {
         if (array_key_exists($charset, $this->cache)) {

src/Platforms/MySQL/CharsetMetadataProvider/ConnectionCharsetMetadataProvider.php

@@ -11,13 +11,28 @@
 /** @internal */
 final class ConnectionCharsetMetadataProvider implements CharsetMetadataProvider
 {
-    public function __construct(private readonly Connection $connection)
+    public function __construct(private readonly Connection $connection, private bool $useUtf8mb3)
     {
     }
 
+    public function normalizeCharset(string $charset): string
+    {
+        if ($this->useUtf8mb3 && $charset === 'utf8') {
+            return 'utf8mb3';
+        }
+
+        if (! $this->useUtf8mb3 && $charset === 'utf8mb3') {
+            return 'utf8';
+        }
+
+        return $charset;
+    }
+
     /** @throws Exception */
     public function getDefaultCharsetCollation(string $charset): ?string
     {
+        $charset = $this->normalizeCharset($charset);
+
         $collation = $this->connection->fetchOne(
             <<<'SQL'
             SELECT DEFAULT_COLLATE_NAME

src/Platforms/MySQL/CollationMetadataProvider.php

@@ -7,5 +7,7 @@
 /** @internal */
 interface CollationMetadataProvider
 {
+    public function normalizeCollation(string $collation): string;
+
     public function getCollationCharset(string $collation): ?string;
 }

src/Platforms/MySQL/CollationMetadataProvider/CachingCollationMetadataProvider.php

@@ -18,6 +18,11 @@
     {
     }
 
+    public function normalizeCollation(string $collation): string
+    {
+        return $this->collationMetadataProvider->normalizeCollation($collation);
+    }
+
     public function getCollationCharset(string $collation): ?string
     {
         if (array_key_exists($collation, $this->cache)) {

src/Platforms/MySQL/CollationMetadataProvider/ConnectionCollationMetadataProvider.php

@@ -8,16 +8,34 @@
 use Doctrine\DBAL\Exception;
 use Doctrine\DBAL\Platforms\MySQL\CollationMetadataProvider;
 
+use function str_starts_with;
+use function substr;
+
 /** @internal */
 final class ConnectionCollationMetadataProvider implements CollationMetadataProvider
 {
-    public function __construct(private readonly Connection $connection)
+    public function __construct(private readonly Connection $connection, private bool $useUtf8mb3)
     {
     }
 
+    public function normalizeCollation(string $collation): string
+    {
+        if ($this->useUtf8mb3 && str_starts_with($collation, 'utf8_')) {
+            return 'utf8mb3' . substr($collation, 4);
+        }
+
+        if (! $this->useUtf8mb3 && str_starts_with($collation, 'utf8mb3_')) {
+            return 'utf8' . substr($collation, 7);
+        }
+
+        return $collation;
+    }
+
     /** @throws Exception */
     public function getCollationCharset(string $collation): ?string
     {
+        $collation = $this->normalizeCollation($collation);
+
         $charset = $this->connection->fetchOne(
             <<<'SQL'
 SELECT CHARACTER_SET_NAME

src/Platforms/MySQL/Comparator.php

@@ -82,10 +82,20 @@ private function normalizeTable(Table $table): Table
      */
     private function normalizeOptions(array $options): array
     {
-        if (isset($options['charset']) && ! isset($options['collation'])) {
-            $options['collation'] = $this->charsetMetadataProvider->getDefaultCharsetCollation($options['charset']);
-        } elseif (isset($options['collation']) && ! isset($options['charset'])) {
-            $options['charset'] = $this->collationMetadataProvider->getCollationCharset($options['collation']);
+        if (isset($options['charset'])) {
+            $options['charset'] = $this->charsetMetadataProvider->normalizeCharset($options['charset']);
+
+            if (! isset($options['collation'])) {
+                $options['collation'] = $this->charsetMetadataProvider->getDefaultCharsetCollation($options['charset']);
+            }
+        }
+
+        if (isset($options['collation'])) {
+            $options['collation'] = $this->collationMetadataProvider->normalizeCollation($options['collation']);
+
+            if (! isset($options['charset'])) {
+                $options['charset'] = $this->collationMetadataProvider->getCollationCharset($options['collation']);
+            }
         }
 
         return $options;

src/Schema/MySQLSchemaManager.php

@@ -316,13 +316,15 @@
     /** @throws Exception */
     public function createComparator(): Comparator
     {
+        $useUtf8mb3 = $this->platform->informationSchemaUsesUtf8mb3($this->connection);
+
         return new MySQL\Comparator(
             $this->platform,
             new CachingCharsetMetadataProvider(
-                new ConnectionCharsetMetadataProvider($this->connection),
+                new ConnectionCharsetMetadataProvider($this->connection, $useUtf8mb3),
             ),
             new CachingCollationMetadataProvider(
-                new ConnectionCollationMetadataProvider($this->connection),
+                new ConnectionCollationMetadataProvider($this->connection, $useUtf8mb3),
             ),
             $this->getDefaultTableOptions(),
         );

tests/Functional/Driver/DBAL6146Test.php

@@ -0,0 +1,85 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\DBAL\Tests\Functional\Driver;
+
+use Doctrine\DBAL\Schema\Column;
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\DBAL\Schema\Table;
+use Doctrine\DBAL\Tests\FunctionalTestCase;
+use Doctrine\DBAL\Tests\TestUtil;
+use Doctrine\DBAL\Types\StringType;
+use PHPUnit\Framework\Attributes\DataProvider;
+
+class DBAL6146Test extends FunctionalTestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        if (TestUtil::isDriverOneOf('pdo_mysql', 'mysqli')) {
+            return;
+        }
+
+        self::markTestSkipped('This test requires the pdo_mysql or the mysqli driver.');
+    }
+
+    /** @return iterable<array{array<string,string>,array<string,string>}> */
+    public static function equivalentCharsetAndCollationProvider(): iterable
+    {
+        yield [[], []];
+        yield [['charset' => 'utf8'], ['charset' => 'utf8']];
+        yield [['charset' => 'utf8'], ['charset' => 'utf8mb3']];
+        yield [['charset' => 'utf8mb3'], ['charset' => 'utf8']];
+        yield [['charset' => 'utf8mb3'], ['charset' => 'utf8mb3']];
+        yield [['collation' => 'utf8_unicode_ci'], ['collation' => 'utf8_unicode_ci']];
+        yield [['collation' => 'utf8_unicode_ci'], ['collation' => 'utf8mb3_unicode_ci']];
+        yield [['collation' => 'utf8mb3_unicode_ci'], ['collation' => 'utf8mb3_unicode_ci']];
+        yield [['collation' => 'utf8mb3_unicode_ci'], ['collation' => 'utf8_unicode_ci']];
+        yield [
+            ['charset' => 'utf8', 'collation' => 'utf8_unicode_ci'],
+            ['charset' => 'utf8', 'collation' => 'utf8_unicode_ci'],
+        ];
+
+        yield [
+            ['charset' => 'utf8', 'collation' => 'utf8_unicode_ci'],
+            ['charset' => 'utf8mb3', 'collation' => 'utf8mb3_unicode_ci'],
+        ];
+
+        yield [
+            ['charset' => 'utf8mb3', 'collation' => 'utf8mb3_unicode_ci'],
+            ['charset' => 'utf8', 'collation' => 'utf8_unicode_ci'],
+        ];
+
+        yield [
+            ['charset' => 'utf8mb3', 'collation' => 'utf8mb3_unicode_ci'],
+            ['charset' => 'utf8mb3', 'collation' => 'utf8mb3_unicode_ci'],
+        ];
+    }
+
+    /**
+     * @param array<string,string> $options1
+     * @param array<string,string> $options2
+     */
+    #[DataProvider('equivalentCharsetAndCollationProvider')]
+    public function testThereAreNoRedundantAlterTableStatements(array $options1, array $options2): void
+    {
+        $column1 = new Column('bar', new StringType(), ['length' => 32, 'platformOptions' => $options1]);
+        $table1  = new Table(name: 'foo6146', columns: [$column1]);
+
+        $column2 = new Column('bar', new StringType(), ['length' => 32, 'platformOptions' => $options2]);
+        $table2  = new Table(name: 'foo6146', columns: [$column2]);
+
+        $this->dropAndCreateTable($table1);
+
+        $schemaManager = $this->connection->createSchemaManager();
+        $oldSchema     = $schemaManager->introspectSchema();
+        $newSchema     = new Schema([$table2]);
+        $comparator    = $schemaManager->createComparator();
+        $schemaDiff    = $comparator->compareSchemas($oldSchema, $newSchema);
+        $alteredTables = $schemaDiff->getAlteredTables();
+
+        self::assertEmpty($alteredTables);
+    }
+}

tests/Platforms/MySQL/CollationMetadataProvider/ConnectionCharsetMetadataProviderTest.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\DBAL\Tests\Platforms\MySQL\CollationMetadataProvider;
+
+use Doctrine\DBAL\Connection;
+use Doctrine\DBAL\Platforms\MySQL\CharsetMetadataProvider\ConnectionCharsetMetadataProvider;
+use PHPUnit\Framework\TestCase;
+
+class ConnectionCharsetMetadataProviderTest extends TestCase
+{
+    public function testNormalizeCharset(): void
+    {
+        $connection = $this->createMock(Connection::class);
+
+        $utf8Provider = new ConnectionCharsetMetadataProvider($connection, false);
+
+        self::assertSame('utf8', $utf8Provider->normalizeCharset('utf8'));
+        self::assertSame('utf8', $utf8Provider->normalizeCharset('utf8mb3'));
+        self::assertSame('foobar', $utf8Provider->normalizeCharset('foobar'));
+
+        $utf8mb3Provider = new ConnectionCharsetMetadataProvider($connection, true);
+
+        self::assertSame('utf8mb3', $utf8mb3Provider->normalizeCharset('utf8'));
+        self::assertSame('utf8mb3', $utf8mb3Provider->normalizeCharset('utf8mb3'));
+        self::assertSame('foobar', $utf8mb3Provider->normalizeCharset('foobar'));
+    }
+}

tests/Platforms/MySQL/CollationMetadataProvider/ConnectionCollationMetadataProviderTest.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\DBAL\Tests\Platforms\MySQL\CollationMetadataProvider;
+
+use Doctrine\DBAL\Connection;
+use Doctrine\DBAL\Platforms\MySQL\CollationMetadataProvider\ConnectionCollationMetadataProvider;
+use PHPUnit\Framework\TestCase;
+
+class ConnectionCollationMetadataProviderTest extends TestCase
+{
+    public function testNormalizeCcollation(): void
+    {
+        $connection = $this->createMock(Connection::class);
+
+        $utf8Provider = new ConnectionCollationMetadataProvider($connection, false);
+
+        self::assertSame('utf8_unicode_ci', $utf8Provider->normalizeCollation('utf8_unicode_ci'));
+        self::assertSame('utf8_unicode_ci', $utf8Provider->normalizeCollation('utf8mb3_unicode_ci'));
+        self::assertSame('foobar_unicode_ci', $utf8Provider->normalizeCollation('foobar_unicode_ci'));
+
+        $utf8mb3Provider = new ConnectionCollationMetadataProvider($connection, true);
+
+        self::assertSame('utf8mb3_unicode_ci', $utf8mb3Provider->normalizeCollation('utf8_unicode_ci'));
+        self::assertSame('utf8mb3_unicode_ci', $utf8mb3Provider->normalizeCollation('utf8mb3_unicode_ci'));
+        self::assertSame('foobar_unicode_ci', $utf8mb3Provider->normalizeCollation('foobar_unicode_ci'));
+    }
+}