fix: SQLite3 Forge::modifyColumn() changes NULL incorrectly

Author: kenjis

system/Database/Forge.php

@@ -897,13 +897,19 @@ protected function _processFields(bool $createTable = false): array
             $this->_attributeDefault($attributes, $field);
 
             if (isset($attributes['NULL'])) {
+                $nullString = ' ' . $this->null;
+
                 if ($attributes['NULL'] === true) {
-                    $field['null'] = empty($this->null) ? '' : ' ' . $this->null;
+                    $field['null'] = empty($this->null) ? '' : $nullString;
+                } elseif ($attributes['NULL'] === $nullString) {
+                    $field['null'] = $nullString;
+                } elseif ($attributes['NULL'] === '') {
+                    $field['null'] = '';
                 } else {
-                    $field['null'] = ' NOT NULL';
+                    $field['null'] = ' NOT ' . $this->null;
                 }
             } elseif ($createTable === true) {
-                $field['null'] = ' NOT NULL';
+                $field['null'] = ' NOT ' . $this->null;
             }
 
             $this->_attributeAutoIncrement($attributes, $field);

system/Database/SQLite3/Table.php

@@ -183,14 +183,14 @@ public function dropColumn($columns)
      *
      * @return Table
      */
-    public function modifyColumn(array $field)
+    public function modifyColumn(array $fields)
     {
-        $field = $field[0];
-
-        $oldName = $field['name'];
-        unset($field['name']);
+        foreach ($fields as $field) {
+            $oldName = $field['name'];
+            unset($field['name']);
 
-        $this->fields[$oldName] = $field;
+            $this->fields[$oldName] = $field;
+        }
 
         return $this;
     }

tests/system/Database/Live/ForgeTest.php

@@ -17,6 +17,7 @@
 use CodeIgniter\Test\DatabaseTestTrait;
 use Config\Database;
 use RuntimeException;
+use stdClass;
 use Tests\Support\Database\Seeds\CITestSeeder;
 
 /**
@@ -1276,6 +1277,50 @@ public function testModifyColumnRename()
         $this->forge->dropTable('forge_test_three', true);
     }
 
+    public function testModifyColumnNull()
+    {
+        if ($this->db->DBDriver === 'SQLSRV') {
+            $this->markTestSkipped('SQLSRV does not support getFieldData() nullable.');
+        }
+
+        $this->forge->dropTable('forge_test_modify', true);
+
+        $this->forge->addField([
+            'col1' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => true],
+            'col2' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => true],
+            'col3' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => true],
+        ]);
+        $this->forge->createTable('forge_test_modify');
+
+        $this->forge->modifyColumn('forge_test_modify', [
+            'col1' => ['type' => 'VARCHAR', 'constraint' => 1],
+            'col2' => ['type' => 'VARCHAR', 'constraint' => 1, 'null' => true],
+            'col3' => ['type' => 'VARCHAR', 'constraint' => 1, 'null' => false],
+        ]);
+
+        $this->db->resetDataCache();
+
+        $col1 = $this->getMetaData('col1', 'forge_test_modify');
+        $this->assertTrue($col1->nullable);
+        $col2 = $this->getMetaData('col2', 'forge_test_modify');
+        $this->assertTrue($col2->nullable);
+        $col3 = $this->getMetaData('col3', 'forge_test_modify');
+        $this->assertFalse($col3->nullable);
+
+        $this->forge->dropTable('forge_test_modify', true);
+    }
+
+    private function getMetaData(string $column, string $table): stdClass
+    {
+        $fields = $this->db->getFieldData($table);
+
+        return $fields[array_search(
+            $column,
+            array_column($fields, 'name'),
+            true
+        )];
+    }
+
     public function testConnectWithArrayGroup()
     {
         $group = config('Database');