feat(mysql/addColumn): supports FIRST keyword (#7943)

docs/migrations.md

@@ -207,6 +207,30 @@ queryInterface.addColumn(
   }
 )
 
+// or with first attribute to put the column at the beginning of the table
+// currently supports only in MySQL
+
+queryInterface.addColumn(
+  'nameOfAnExistingTable',
+  'nameOfTheNewAttribute',
+  {
+    type: Sequelize.STRING,
+    first: true
+  }
+)
+
+// or with after attribute to put the column after a specific column
+// currently supports only in MySQL
+
+queryInterface.addColumn(
+  'nameOfAnExistingTable',
+  'nameOfTheNewAttribute',
+  {
+    type: Sequelize.STRING,
+    after: 'nameOfAnExistingColumn'
+  }
+)
+
 // or with an explicit schema:
 
 queryInterface.addColumn({

lib/dialects/mysql/query-generator.js

@@ -104,6 +104,7 @@ const QueryGenerator = {
       tableName: table,
       foreignKey: key
     });
+
     return `ALTER TABLE ${this.quoteTable(table)} ADD ${this.quoteIdentifier(key)} ${definition};`;
   },
 
@@ -251,6 +252,9 @@ const QueryGenerator = {
       template += ' PRIMARY KEY';
     }
 
+    if (attribute.first) {
+      template += ' FIRST';
+    }
     if (attribute.after) {
       template += ' AFTER ' + this.quoteIdentifier(attribute.after);
     }

test/unit/sql/add-column.test.js

@@ -42,6 +42,14 @@ if (current.dialect.name === 'mysql') {
         });
       });
 
+      it('properly generate alter queries with FIRST', () => {
+        return expectsql(sql.addColumnQuery(Model.getTableName(), 'test_added_col_first', current.normalizeAttribute({
+          type: DataTypes.STRING,
+          first: true
+        })), {
+          mysql: 'ALTER TABLE `users` ADD `test_added_col_first` VARCHAR(255) FIRST;'
+        });
+      });
     });
   });
 }