feat: During migrations, add new columns in the user-defined position

The "user-defined position" refers to the position in which columns
are defined in the `columns` property of the `schema` object.

Author: nwoltman

lib/TableDefinition.js

@@ -118,6 +118,7 @@ class TableDefinition {
     const newSchema = this._schema;
     const operations = [];
     const renamedColumns = []; // List of old column names
+    var lastColumnName = null;
     var columnName;
 
     // Add new columns and modify existing columns
@@ -129,9 +130,10 @@ class TableDefinition {
       const oldColumnDefinition = oldSchema.columns[oldColumnName];
 
       if (!oldColumnDefinition) {
+        const position = lastColumnName ? ' AFTER ' + pool.escapeId(lastColumnName) : ' FIRST';
         operations.push(Operation.create(
           Operation.Types.ADD_COLUMN,
-          'ADD COLUMN ' + pool.escapeId(columnName) + ' ' + newColumnDefinition.$toSQL()
+          'ADD COLUMN ' + pool.escapeId(columnName) + ' ' + newColumnDefinition.$toSQL() + position
         ));
       } else if (columnName !== oldColumnName) {
         operations.push(Operation.create(
@@ -147,6 +149,8 @@ class TableDefinition {
           [columnName]
         ));
       }
+
+      lastColumnName = columnName;
     }
 
     // Drop old columns (unless the column is being changed)

test/integration/MySQLPlus.test.js

@@ -454,11 +454,11 @@ describe('MySQLPlus', function() {
     '  `c` bigint(20) unsigned DEFAULT NULL,\n' +
     '  `d` bigint(5) unsigned NOT NULL,\n' +
     '  `ai` int(11) DEFAULT NULL,\n' +
+    '  `ci` char(1) DEFAULT NULL,\n' +
     '  `eb` varchar(63) DEFAULT NULL,\n' +
     '  `fb` char(1) DEFAULT \'a\',\n' +
     '  `gc` bigint(5) unsigned NOT NULL,\n' +
     '  `hc` varchar(255) NOT NULL,\n' +
-    '  `ci` char(1) DEFAULT NULL,\n' +
     '  UNIQUE KEY `unique_fk_table_eb_fb` (`eb`,`fb`),\n' +
     '  KEY `index_fk_table_c` (`c`),\n' +
     '  KEY `index_fk_table_d` (`d`),\n' +

test/integration/newColumnPositioning.test.js

@@ -0,0 +1,67 @@
+'use strict';
+
+const MySQLPlus = require('../../lib/MySQLPlus');
+
+const config = require('../config');
+
+const ColTypes = MySQLPlus.ColTypes;
+
+describe('when adding new columns', function() {
+
+  const pool = MySQLPlus.createPool(config);
+  const pool2 = MySQLPlus.createPool(config);
+
+  pool.defineTable('new_columns_positioning_test', {
+    columns: {
+      a: ColTypes.int(),
+      b: ColTypes.int(),
+    },
+  });
+  pool2.defineTable('new_columns_positioning_test', {
+    columns: {
+      preA: ColTypes.smallint(),
+      a: ColTypes.int(),
+      preB: ColTypes.smallint(),
+      b: ColTypes.int(),
+      c: ColTypes.smallint(),
+    },
+  });
+
+  before(done => {
+    pool.sync(err => {
+      if (err) {
+        throw err;
+      }
+
+      pool.end(done);
+    });
+  });
+
+  after(done => pool2.end(done));
+
+  it('should add the columns in the same position that they are defined in the JS columns object', done => {
+    pool2.sync(err => {
+      if (err) {
+        throw err;
+      }
+
+      pool2.query('SHOW CREATE TABLE `new_columns_positioning_test`', (err, rows) => {
+        if (err) {
+          throw err;
+        }
+
+        rows[0]['Create Table'].should.equal(
+          'CREATE TABLE `new_columns_positioning_test` (\n' +
+          '  `preA` smallint(6) DEFAULT NULL,\n' +
+          '  `a` int(11) DEFAULT NULL,\n' +
+          '  `preB` smallint(6) DEFAULT NULL,\n' +
+          '  `b` int(11) DEFAULT NULL,\n' +
+          '  `c` smallint(6) DEFAULT NULL\n' +
+          ') ENGINE=InnoDB DEFAULT CHARSET=utf8'
+        );
+        done();
+      });
+    });
+  });
+
+});

test/unit/TableDefinition.test.js

@@ -139,7 +139,7 @@ describe('TableDefinition', () => {
             sql: 'ALTER TABLE `' + existingTableName + '`\n' +
               '       DROP PRIMARY KEY,\n' +
               '       MODIFY COLUMN `id` int unsigned NOT NULL,\n' +
-              '       ADD COLUMN `newCol` tinyint',
+              '       ADD COLUMN `newCol` tinyint AFTER `id`',
             columns: undefined,
           },
         ];