PHPORM-68 Fix partial value un exist validator

src/Validation/DatabasePresenceVerifier.php

@@ -43,8 +43,13 @@ public function getCount($collection, $column, $value, $excludeId = null, $idCol
      */
     public function getMultiCount($collection, $column, array $values, array $extra = [])
     {
-        // Generates a regex like '/(a|b|c)/i' which can query multiple values
-        $regex = '/('.implode('|', $values).')/i';
+        // Nothing can match an empty array. Return early to avoid matching an empty string.
+        if ($values === []) {
+            return 0;
+        }
+
+        // Generates a regex like '/^(a|b|c)$/i' which can query multiple values
+        $regex = new Regex('^('.implode('|', array_map(preg_quote(...), $values)).')$', 'i');
 
         $query = $this->table($collection)->where($column, 'regex', $regex);
 

tests/ValidationTest.php

@@ -103,5 +103,31 @@ public function testExists(): void
             ['name' => 'required|exists:users']
         );
         $this->assertFalse($validator->fails());
+
+        $validator = Validator::make(
+            ['name' => ['test name', 'john']], // Part of an existing value
+            ['name' => 'required|exists:users']
+        );
+        $this->assertTrue($validator->fails());
+
+        $validator = Validator::make(
+            ['name' => '(invalid regex{'],
+            ['name' => 'required|exists:users']
+        );
+        $this->assertTrue($validator->fails());
+
+        $validator = Validator::make(
+            ['name' => ['foo', '(invalid regex{']],
+            ['name' => 'required|exists:users']
+        );
+        $this->assertTrue($validator->fails());
+
+        User::create(['name' => '']);
+
+        $validator = Validator::make(
+            ['name' => []],
+            ['name' => 'exists:users']
+        );
+        $this->assertFalse($validator->fails());
     }
 }