feat: support rollback, fix #1

Author: antfu

src/index.ts

@@ -1,13 +1,20 @@
+/* eslint-disable ts/no-unsafe-declaration-merging */
 import type { DecodedSourceMap, MagicStringOptions, SourceMap, SourceMapOptions } from 'magic-string'
 import MagicString from 'magic-string'
 import remapping from '@ampproject/remapping'
 
 // Thanks to @sxzz & @starknt for the solution
-// eslint-disable-next-line ts/no-unsafe-declaration-merging
 export default interface MagicStringStack extends MagicString {}
-// eslint-disable-next-line ts/no-unsafe-declaration-merging
 export default class MagicStringStack implements MagicString {
+  /**
+   * The stack of MagicString instances.
+   * Lastest instance is pushed to the front of the array.
+   */
   private _stack: MagicString[] = []
+  /**
+   * Prepresents the current MagicString instance.
+   * It should be in the this._stack[0]
+   */
   private _current: MagicString
 
   constructor(
@@ -44,6 +51,16 @@ export default class MagicStringStack implements MagicString {
     this._stack.unshift(newOne)
   }
 
+  /**
+   * Rollback to the previous commit.
+   */
+  rollback() {
+    if (this._stack.length <= 1)
+      throw new Error('Cannot rollback on the first commit')
+    this._stack.shift()
+    this._current = this._stack[0]
+  }
+
   get original() {
     return this._current.original
   }

test/index.test.ts

@@ -23,6 +23,8 @@ it('should work', () => {
   expect(ss.toString()).toMatchInlineSnapshot(`"answer = 42"`)
 
   ss.commit()
+  ss.commit() // empty commit
+  ss.commit() // empty commit
 
   s.prepend('var ').append(';')
   ss.prepend('var ').append(';')
@@ -69,11 +71,23 @@ it('replace after replace', () => {
     `)
 })
 
-it('should be sub instance', () => {
+it('should be sub instance of MagicString', () => {
   const s = new MagicStringStack('')
   expect(s instanceof MagicString).toBe(true)
 })
 
+it('should support clone', () => {
+  const s = new MagicStringStack('hello world')
+  s.update(0, 5, 'goodbye')
+  s.commit()
+  const s2 = s.clone()
+  expect(s.generateMap()).toEqual(s2.generateMap())
+  s2.update(8, 13, 'there')
+  s2.commit()
+  expect(s.toString()).toBe('goodbye world')
+  expect(s2.toString()).toBe('goodbye there')
+})
+
 function removeEmptyKeys(obj: any) {
   return Object.fromEntries(Object.entries(obj).filter(([_, v]) => !(v == null || (Array.isArray(v) && !v.length))))
 }