\assert() 利用を排除し設計レベルの型保証に置換

\assert() は production で no-op になり silent pass を許す可能性があるため、
全 6 箇所を CLAUDE.md「設計や言語機能で型エラーを解決する」方針に沿って
置き換えた。

src 側:
- Connection::query: fetchAll の row 型 narrowing を if + throw に変更
  (FETCH_ASSOC コントラクト違反時 UnexpectedValueException で fast-fail)
- Connection::dialect / serverVersion: ??= による lazy init に再設計
  ensureDialectDetected() を probeServerVersion() に置換し、nullable
  narrowing を不要にした。SELECT VERSION() の実行回数は変わらない
  (どちらの getter を先に呼んでも 1 回)

test 側:
- ConnectionTest::countUsers: テストヘルパーの \assert() を PHPUnit
  assertion (assertNotFalse / assertIsArray / assertIsInt) に変更
- 防御コードと挙動保証のテスト 3 件を追加:
  - testServerVersionCachesResultAcrossCalls (キャッシュ対称性)
  - testDialectAndServerVersionShareSingleSelectVersionQuery
    (??= リファクタの単一 SELECT VERSION() 実行不変条件)
  - testQueryThrowsWhenPdoReturnsNonArrayRow (FETCH_ASSOC 防御コード)

機能変更なし。公開 API 変更なし。

Author: logicraft

src/Sloop/Database/Connection.php

@@ -15,6 +15,7 @@
 use Sloop\Database\Exception\ExceptionFactory;
 use Sloop\Database\Exception\LockWaitTimeoutException;
 use Throwable;
+use UnexpectedValueException;
 
 /**
  * PDO wrapper exposing sloop's database API.
@@ -107,19 +108,20 @@ public static function open(
     /**
      * Execute a SELECT-style statement and return the fetched rows.
      *
-     * @param  string                   $sql      SQL statement returning a result set
-     * @param  array<int|string, mixed> $bindings Parameters to bind
-     * @return Result                   Fetched rows
-     * @throws DatabaseException        When the statement fails
+     * @param  string                    $sql      SQL statement returning a result set
+     * @param  array<int|string, mixed>  $bindings Parameters to bind
+     * @return Result                    Fetched rows
+     * @throws DatabaseException         When the statement fails
+     * @throws UnexpectedValueException  When PDO returns a non-array row under FETCH_ASSOC (driver contract violation)
      */
     public function query(string $sql, array $bindings = []): Result
     {
         $stmt = $this->prepareAndExecute($sql, $bindings);
-        // PDOStatement::fetchAll's stub only exposes `array`, so per-row
-        // assert is required to narrow to Result's parameter type.
         $rows = [];
         foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $row) {
-            \assert(\is_array($row));
+            if (!\is_array($row)) {
+                throw new UnexpectedValueException('PDO returned non-array row from FETCH_ASSOC');
+            }
             $rows[] = $row;
         }
 
@@ -294,11 +296,7 @@ public function transaction(
      */
     public function dialect(): Dialect
     {
-        $this->ensureDialectDetected();
-
-        \assert($this->dialect !== null);
-
-        return $this->dialect;
+        return $this->dialect ??= Dialect::detect($this->serverVersion());
     }
 
     /**
@@ -311,11 +309,7 @@ public function dialect(): Dialect
      */
     public function serverVersion(): string
     {
-        $this->ensureDialectDetected();
-
-        \assert($this->serverVersion !== null);
-
-        return $this->serverVersion;
+        return $this->serverVersion ??= $this->probeServerVersion();
     }
 
     /**
@@ -387,17 +381,13 @@ private function sleepBackoff(int $backoffMs): void
     }
 
     /**
-     * Probe the server version on first use and cache the result.
+     * Probe the server version via `SELECT VERSION()`; called lazily by serverVersion().
      *
-     * @return void
+     * @return string            Raw `SELECT VERSION()` output, or '' if the driver returned false instead of throwing
      * @throws DatabaseException When `SELECT VERSION()` fails
      */
-    private function ensureDialectDetected(): void
+    private function probeServerVersion(): string
     {
-        if ($this->dialect !== null) {
-            return;
-        }
-
         try {
             $statement = $this->pdo->query('SELECT VERSION()');
         } catch (PDOException $e) {
@@ -406,10 +396,7 @@ private function ensureDialectDetected(): void
 
         // Defensive: unreachable under ERRMODE_EXCEPTION (contractual for open()),
         // but tolerate callers that inject a PDO with a different error mode.
-        $value = $statement === false ? '' : (string) $statement->fetchColumn();
-
-        $this->serverVersion = $value;
-        $this->dialect       = Dialect::detect($value);
+        return $statement === false ? '' : (string) $statement->fetchColumn();
     }
 
     /**

tests/Unit/Database/ConnectionTest.php

@@ -7,6 +7,7 @@
 use LogicException;
 use PDO;
 use Pdo\Sqlite;
+use PDOStatement;
 use PHPUnit\Framework\TestCase;
 use RuntimeException;
 use Sloop\Database\Connection;
@@ -16,6 +17,7 @@
 use Sloop\Database\Exception\LockWaitTimeoutException;
 use Sloop\Database\Exception\QueryException;
 use Sloop\Database\IsolationLevel;
+use UnexpectedValueException;
 
 /*
  * Policy: several tests below omit a trailing $this->fail() inside the try
@@ -55,13 +57,15 @@ protected function setUp(): void
     private function countUsers(): int
     {
         $stmt = $this->pdo->query('SELECT COUNT(*) AS c FROM users');
-        \assert($stmt !== false);
+        $this->assertNotFalse($stmt);
+
         $row = $stmt->fetch(PDO::FETCH_ASSOC);
-        \assert(\is_array($row));
+        $this->assertIsArray($row);
+
         $count = $row['c'] ?? 0;
-        \assert(\is_int($count) || \is_string($count));
+        $this->assertIsInt($count);
 
-        return (int) $count;
+        return $count;
     }
 
     // -------------------------------------------------------
@@ -136,6 +140,31 @@ public function testQueryReturnsEmptyResultWhenNoRowsMatch(): void
         $this->assertSame([], $result->toArray());
     }
 
+    public function testQueryThrowsWhenPdoReturnsNonArrayRow(): void
+    {
+        // Defensive guard: FETCH_ASSOC contractually returns associative arrays,
+        // but the throw is the type-narrowing fallback when a non-conformant
+        // driver violates that contract.
+        $statement = $this->createStub(PDOStatement::class);
+        $statement->method('execute')->willReturn(true);
+        $statement->method('fetchAll')->willReturn([['valid' => 1], 'invalid-row']);
+
+        $pdo = $this->createStub(PDO::class);
+        $pdo->method('prepare')->willReturn($statement);
+
+        $connection = new Connection($pdo, 'test');
+
+        try {
+            $connection->query('SELECT 1');
+            $this->fail('Expected UnexpectedValueException');
+        } catch (UnexpectedValueException $e) {
+            $this->assertSame(
+                'PDO returned non-array row from FETCH_ASSOC',
+                $e->getMessage(),
+            );
+        }
+    }
+
     public function testStatementReturnsAffectedRowCount(): void
     {
         $affected = $this->connection->statement(
@@ -490,6 +519,39 @@ public function testDialectCachesResultAcrossCalls(): void
         $this->assertSame($first, $second);
     }
 
+    public function testServerVersionCachesResultAcrossCalls(): void
+    {
+        $first  = $this->connection->serverVersion();
+        $second = $this->connection->serverVersion();
+
+        $this->assertSame($first, $second);
+    }
+
+    public function testDialectAndServerVersionShareSingleSelectVersionQuery(): void
+    {
+        // Both getters are independently lazy via ??= but must share a single
+        // `SELECT VERSION()` execution regardless of which is called first or
+        // how many times callers interleave them.
+        $statement = $this->createStub(PDOStatement::class);
+        $statement->method('fetchColumn')->willReturn('10.11.11-MariaDB');
+
+        $pdo = $this->createMock(PDO::class);
+        $pdo->expects($this->once())
+            ->method('query')
+            ->with('SELECT VERSION()')
+            ->willReturn($statement);
+
+        $connection = new Connection($pdo, 'test');
+
+        $connection->serverVersion();
+        $connection->dialect();
+        $connection->serverVersion();
+        $connection->dialect();
+
+        $this->assertSame(Dialect::MariaDB, $connection->dialect());
+        $this->assertSame('10.11.11-MariaDB', $connection->serverVersion());
+    }
+
     public function testDialectFallsBackToMysqlWhenVersionLacksMariadbMarker(): void
     {
         $sqlite = new Sqlite('sqlite::memory:', null, null, [