Fix up decimal migration_diff

Author: dereuromark

src/Command/BakeMigrationDiffCommand.php

@@ -300,11 +300,38 @@ protected function getColumns(): void
                         }
                     }
 
-                    if (isset($changedAttributes['length'])) {
+                    // For decimal columns, handle CakePHP schema -> migration attribute mapping
+                    if ($column['type'] === 'decimal') {
+                        // In CakePHP schema: 'length' = precision, 'precision' = scale
+                        // In migrations: 'precision' = precision, 'scale' = scale
+
+                        // Convert CakePHP schema's 'precision' (which is scale) to migration's 'scale'
+                        if (isset($changedAttributes['precision'])) {
+                            $changedAttributes['scale'] = $changedAttributes['precision'];
+                            unset($changedAttributes['precision']);
+                        }
+
+                        // Convert CakePHP schema's 'length' (which is precision) to migration's 'precision'
+                        if (isset($changedAttributes['length'])) {
+                            $changedAttributes['precision'] = $changedAttributes['length'];
+                            unset($changedAttributes['length']);
+                        }
+
+                        // Ensure both precision and scale are always set for decimal columns
+                        if (!isset($changedAttributes['precision']) && isset($column['length'])) {
+                            $changedAttributes['precision'] = $column['length'];
+                        }
+                        if (!isset($changedAttributes['scale']) && isset($column['precision'])) {
+                            $changedAttributes['scale'] = $column['precision'];
+                        }
+
+                        // Remove 'limit' for decimal columns as they use precision/scale instead
+                        unset($changedAttributes['limit']);
+                    } elseif (isset($changedAttributes['length'])) {
+                        // For non-decimal columns, convert 'length' to 'limit'
                         if (!isset($changedAttributes['limit'])) {
                             $changedAttributes['limit'] = $changedAttributes['length'];
                         }
-
                         unset($changedAttributes['length']);
                     }
 

tests/TestCase/Command/BakeMigrationDiffCommandTest.php

@@ -57,10 +57,19 @@ public function tearDown(): void
                 unlink($file);
             }
         }
+
+        $defaultMigrationsPath = ROOT . DS . 'config' . DS . 'Migrations' . DS;
+        $migrationFiles = glob($defaultMigrationsPath . '*TheDiff*.php') ?: [];
+        foreach ($migrationFiles as $file) {
+            if (file_exists($file)) {
+                unlink($file);
+            }
+        }
+
         if (env('DB_URL_COMPARE')) {
             // Clean up the comparison database each time. Table order is important.
             $connection = ConnectionManager::get('test_comparisons');
-            $tables = ['articles', 'categories', 'comments', 'users', 'orphan_table', 'phinxlog', 'tags', 'test_blog_phinxlog'];
+            $tables = ['articles', 'categories', 'comments', 'users', 'orphan_table', 'phinxlog', 'tags', 'test_blog_phinxlog', 'test_decimal_types'];
             foreach ($tables as $table) {
                 $connection->execute("DROP TABLE IF EXISTS $table");
             }
@@ -240,6 +249,17 @@ public function testBakingDiffWithAutoIdIncompatibleUnsignedPrimaryKeys(): void
         $this->runDiffBakingTest('WithAutoIdIncompatibleUnsignedPrimaryKeys');
     }
 
+    /**
+     * Tests baking a diff with decimal column changes
+     * Regression test for issue #659
+     */
+    public function testBakingDiffDecimalChange(): void
+    {
+        $this->skipIf(!env('DB_URL_COMPARE'));
+
+        $this->runDiffBakingTest('DecimalChange');
+    }
+
     /**
      * Tests that baking a diff with --plugin option only includes tables with Table classes
      */

tests/comparisons/Diff/decimalChange/mysql/the_diff_decimal_change.php

@@ -0,0 +1,49 @@
+<?php
+declare(strict_types=1);
+
+use Migrations\BaseMigration;
+
+class TheDiffDecimalChange extends BaseMigration
+{
+    /**
+     * Up Method.
+     *
+     * More information on this method is available here:
+     * https://book.cakephp.org/migrations/5/en/migrations.html#the-up-method
+     *
+     * @return void
+     */
+    public function up(): void
+    {
+        $this->table('test_decimal_types')
+            ->changeColumn('amount', 'decimal', [
+                'default' => null,
+                'null' => false,
+                'precision' => 10,
+                'scale' => 2,
+                'signed' => true,
+            ])
+            ->update();
+    }
+
+    /**
+     * Down Method.
+     *
+     * More information on this method is available here:
+     * https://book.cakephp.org/migrations/5/en/migrations.html#the-down-method
+     *
+     * @return void
+     */
+    public function down(): void
+    {
+        $this->table('test_decimal_types')
+            ->changeColumn('amount', 'decimal', [
+                'default' => null,
+                'null' => false,
+                'precision' => 5,
+                'scale' => 2,
+                'signed' => true,
+            ])
+            ->update();
+    }
+}

tests/comparisons/Diff/decimalChange/schema-dump-test_comparisons_mysql.lock

@@ -0,0 +1,40 @@
+<?php
+declare(strict_types=1);
+
+use Migrations\BaseMigration;
+
+class TheDiffDecimalChangeMysql extends BaseMigration
+{
+    /**
+     * Up Method.
+     *
+     * More information on this method is available here:
+     * https://book.cakephp.org/migrations/5/en/migrations.html#the-up-method
+     *
+     * @return void
+     */
+    public function up(): void
+    {
+        $this->table('test_decimal_types')
+            ->addColumn('amount', 'decimal', [
+                'default' => null,
+                'null' => false,
+                'precision' => 5,
+                'scale' => 2,
+            ])
+            ->create();
+    }
+
+    /**
+     * Down Method.
+     *
+     * More information on this method is available here:
+     * https://book.cakephp.org/migrations/5/en/migrations.html#the-down-method
+     *
+     * @return void
+     */
+    public function down(): void
+    {
+        $this->table('test_decimal_types')->drop()->save();
+    }
+}