Allow to use Sign::in with an empty array

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## [Unreleased]
+
+## Added
+
+- It is now possible to use an empty array when using `Sign::in` in a specification
+
 ## 5.2.0 - 2026-05-14
 
 ### Changed

proofs/query/where.php

@@ -585,4 +585,25 @@ static function($assert) {
                 static fn() => null,
             ));
         });
+
+    yield $prove
+        ->proof('Where condition with no values for an "in" sign will match nothing')
+        ->given(
+            Column::any(),
+        )
+        ->test(static function($assert, $column) {
+            $specification = Property::of(
+                $column->name()->toString(),
+                Sign::in,
+                [],
+            );
+            $where = Where::of($specification);
+
+            [$sql, $parameters] = $where->normalize(Driver::mysql);
+            $assert->same(
+                "WHERE {$column->name()->sql(Driver::mysql)} IN (SELECT NULL WHERE false)",
+                $sql,
+            );
+            $assert->same(0, $parameters->size());
+        });
 };

properties/Connection.php

@@ -68,6 +68,7 @@ public static function list(): array
             Connection\SelectWhereEndsWith::class,
             Connection\SelectWhereContains::class,
             Connection\SelectWhereIn::class,
+            Connection\SelectWhereInNothing::class,
             Connection\SelectWhereInQuery::class,
             Connection\SelectOffset::class,
             Connection\SelectLimit::class,

properties/Connection/SelectWhereInNothing.php

@@ -0,0 +1,78 @@
+<?php
+declare(strict_types = 1);
+
+namespace Properties\Formal\AccessLayer\Connection;
+
+use Formal\AccessLayer\{
+    Query\Insert,
+    Query\Select,
+    Table\Name,
+    Row,
+    Connection,
+};
+use Innmind\Specification\{
+    Comparator,
+    Sign,
+};
+use Innmind\BlackBox\{
+    Property,
+    Set,
+    Runner\Assert,
+};
+
+/**
+ * @implements Property<Connection>
+ */
+final class SelectWhereInNothing implements Property
+{
+    private string $uuid;
+    private string $username;
+    private int $number;
+
+    public function __construct(string $uuid, string $username, int $number)
+    {
+        $this->uuid = $uuid;
+        $this->username = $username;
+        $this->number = $number;
+    }
+
+    public static function any(): Set
+    {
+        return Set::compose(
+            static fn(...$args) => new self(...$args),
+            Set::uuid(),
+            Set::strings()
+                ->madeOf(Set::strings()->chars()->ascii())
+                ->between(0, 255),
+            Set::integers(),
+        );
+    }
+
+    public function applicableTo(object $connection): bool
+    {
+        return true;
+    }
+
+    public function ensureHeldBy(Assert $assert, object $connection): object
+    {
+        $_ = $connection(Insert::into(
+            Name::of('test'),
+            Row::of([
+                'id' => $this->uuid,
+                'username' => $this->username,
+                'registerNumber' => $this->number,
+            ]),
+        ));
+
+        $select = Select::from(Name::of('test'))->where(Comparator\Property::of(
+            'test.id',
+            Sign::in,
+            [],
+        ));
+        $rows = $connection($select);
+
+        $assert->same(0, $rows->size());
+
+        return $connection;
+    }
+}

src/Query/Where.php

@@ -218,7 +218,10 @@ private function buildInSql(
         return \sprintf(
             '%s IN (%s)',
             $this->buildColumn($driver, $specification),
-            \implode(', ', $placeholders),
+            match ($placeholders) {
+                [] => 'SELECT NULL WHERE false',
+                default => \implode(', ', $placeholders),
+            },
         );
     }