Added exception for missing sub select alias

src/Expression/Table.php

@@ -5,10 +5,10 @@
 namespace Semperton\Query\Expression;
 
 use Closure;
+use InvalidArgumentException;
 use Semperton\Query\ExpressionInterface;
 use Semperton\Query\QueryFactory;
 use Semperton\Query\Type\SelectQuery;
-use RuntimeException;
 
 use function is_string;
 use function implode;
@@ -31,6 +31,10 @@ public function __construct(QueryFactory $factory)
 	 */
 	public function add($table, string $alias = ''): self
 	{
+		if ($table instanceof Closure && $alias === '') {
+			throw new InvalidArgumentException('Alias cannot be empty for sub select');
+		}
+
 		$this->tables[] = [$table, $alias];
 		return $this;
 	}
@@ -71,9 +75,6 @@ public function compile(array &$params = []): string
 					$sql[] = $table . ' ' . $this->factory->quoteIdentifier($alias);
 				}
 			} else {
-				if ($alias === '') {
-					throw new RuntimeException('Alias is required for sub select');
-				}
 
 				$subSelect = new SelectQuery($this->factory);
 				$table($subSelect);

src/Type/SelectQuery.php

@@ -260,7 +260,7 @@ public function compile(array &$params = []): string
 
 		if ($this->where->isValid()) {
 			$sql[] = 'where';
-			$sql[] =  $this->where->compile($params);
+			$sql[] = $this->where->compile($params);
 		}
 
 		if (!!$this->groupBy) {

tests/ExpressionTest.php

@@ -5,7 +5,9 @@
 use PHPUnit\Framework\TestCase;
 use Semperton\Query\Expression\Field;
 use Semperton\Query\Expression\Filter;
+use Semperton\Query\Expression\Table;
 use Semperton\Query\QueryFactory;
+use Semperton\Query\Type\SelectQuery;
 
 final class ExpressionTest extends TestCase
 {
@@ -107,4 +109,21 @@ public function testIndentifier(): void
 
 		$this->assertEquals('"table".*', $ident->compile());
 	}
+
+	public function testTable(): void
+	{
+		$this->expectException(InvalidArgumentException::class);
+		$factory = new QueryFactory();
+		$table = new Table($factory);
+
+		$table->add(function (SelectQuery $query) {
+			$query->from('user')->where('id', '>', 3);
+		}, 'users');
+
+		$this->assertEquals('(select * from user where id > :p1) users', $table->compile());
+
+		$table->reset();
+		$table->add(function (SelectQuery $query) {
+		});
+	}
 }