Remove null collate option from generated migrations

When baking migration diffs, the collate option was included in
column options even when null. This caused "collate is not a valid
column option" errors when running migrations on PostgreSQL.

Fixes #974

Author: dereuromark

src/View/Helper/MigrationHelper.php

@@ -401,6 +401,9 @@ public function getColumnOption(array $options): array
         if (empty($columnOptions['autoIncrement'])) {
             unset($columnOptions['autoIncrement']);
         }
+        if (empty($columnOptions['collate'])) {
+            unset($columnOptions['collate']);
+        }
 
         // currently only MySQL supports the signed option
         $driver = $connection->getDriver();

tests/TestCase/View/Helper/MigrationHelperTest.php

@@ -14,6 +14,7 @@
 namespace Migrations\Test\TestCase\View\Helper;
 
 use Cake\Database\Driver\Mysql;
+use Cake\Database\Driver\Postgres;
 use Cake\Database\Driver\Sqlserver;
 use Cake\Database\Schema\Collection;
 use Cake\Datasource\ConnectionManager;
@@ -397,4 +398,26 @@ public function testStringifyList()
             ],
         ]));
     }
+
+    /**
+     * Test that getColumnOption removes null collate for all databases
+     *
+     * @see https://github.com/cakephp/migrations/issues/974
+     */
+    public function testGetColumnOptionRemovesNullCollate(): void
+    {
+        $options = [
+            'length' => 255,
+            'null' => true,
+            'default' => null,
+            'collate' => null,
+        ];
+
+        $result = $this->helper->getColumnOption($options);
+
+        // collate => null should NOT be in the output for any database
+        // because it causes "collate is not a valid column option" error
+        $this->assertArrayNotHasKey('collate', $result, 'collate => null should be removed');
+        $this->assertArrayNotHasKey('collation', $result, 'collation should not be set when collate is null');
+    }
 }