⚡ perf(vscode): 标差异时旧版本的解析结果按旧内容记着，晚到的答案、翻译插件没变就不再重新解析

vscode/src/codeReader/diff/previewDiff.test.ts

@@ -23,11 +23,12 @@ function base(text: string | null, key = 'k'): DiffBase & { read: ReturnType<typ
   return { label: '上一次提交', key, read: vi.fn(async () => text), missing: '上一次提交里没有这个文件' }
 }
 
-function setup(current: { base: DiffBase | undefined }) {
+function setup(current: { base: DiffBase | undefined, inputs?: string }) {
   const posted: (DocumentDiff | null)[] = []
   const reports: string[] = []
-  const diff = new PreviewDiff(() => current.base, parse, value => posted.push(value), message => reports.push(message))
-  return { diff, posted, reports }
+  const read = vi.fn(parse)
+  const diff = new PreviewDiff(() => current.base, read, () => current.inputs ?? '', value => posted.push(value), message => reports.push(message))
+  return { diff, posted, reports, read }
 }
 
 describe('previewDiff', () => {
@@ -75,6 +76,24 @@ describe('previewDiff', () => {
     expect(second.read).toHaveBeenCalledTimes(1)
   })
 
+  it('旧版本解析出来的按旧内容和解析时看的东西（翻译插件、晚到的答案……）记着：都没变不再解析，哪个变了重新解析', async () => {
+    const current: { base: DiffBase | undefined, inputs: string } = { base: base('x = 1\n', 'a'), inputs: 'v1' }
+    const { diff, posted, read } = setup(current)
+    await diff.update(await sent('x = 2\n', 1))
+    await diff.update(await sent('x = 3\n', 2))
+    expect(read).toHaveBeenCalledTimes(1)
+    expect(posted.at(-1)).toMatchObject({ version: 2, stats: { mod: 1 } })
+    current.inputs = 'v2'
+    await diff.update(await sent('x = 3\n', 3))
+    expect(read).toHaveBeenCalledTimes(2)
+    current.base = base('y = 1\n', 'b')
+    await diff.update(await sent('x = 3\n', 4))
+    expect(read).toHaveBeenCalledTimes(3)
+    current.base = base('y = 1\n', 'c')
+    await diff.update(await sent('x = 3\n', 5))
+    expect(read).toHaveBeenCalledTimes(3)
+  })
+
   it('同一份文档、同一个基准不再比', async () => {
     const { diff, posted } = setup({ base: base('x = 1\n') })
     const doc = await sent('x = 2\n')

vscode/src/codeReader/diff/previewDiff.ts

@@ -61,12 +61,14 @@ export function documentDiff(base: DiffBase, sent: SentDocument, old: { source:
 
 /**
  * 一个打开着的预览的差异：每发出一份文档之后、对比基准变了之后按眼下的基准重新比，比完再发，预览先照常画、不等它。
- * 取过的旧内容按基准的 key 记着（编辑时不用每次去问 git），旧版本每次重新解析：规则查到的定义、调用的种类这些晚到的答案两边要一样。
- * 这里不碰 VS Code。
+ * 取过的旧内容按基准的 key 记着（编辑时不用每次去问 git）；旧版本解析出来的按旧内容和解析时还看的东西（oldInputs）记着，
+ * 都没变不再解析，规则查到的定义、调用的种类这些晚到的答案变了才重新解析，两边同样的写法翻得一样。这里不碰 VS Code。
  */
 export class PreviewDiff {
   /** 取过的旧内容；key 相同不再取，取失败了下次重取 */
   private old: { key: string, text: Promise<string | null> } | undefined
+  /** 解析过的旧版本；旧内容、oldInputs 都没变不再解析，解析出错了下次重来 */
+  private parsed: { text: string, inputs: string, document: Promise<OldDocument | undefined> } | undefined
   /** 只发最后一次比的结果：慢的旧结果不能盖掉新的 */
   private latest = 0
   /** 上一次比的是哪份文档、哪个基准：都没变就不再比（git 状态变了、基准没挪） */
@@ -79,6 +81,8 @@ export class PreviewDiff {
     private readonly baseOf: () => DiffBase | undefined,
     /** 用这份文档的语言、翻译插件和库规则解析旧版本；解析失败是 undefined */
     private readonly readOld: (source: string) => Promise<OldDocument | undefined>,
+    /** 解析旧版本除了旧内容还看的东西（翻译插件、项目入口、晚到的答案）拼成的一串：变了旧版本要重新解析 */
+    private readonly oldInputs: () => string,
     private readonly post: (diff: DocumentDiff | null) => void,
     private readonly report: (message: string) => void,
   ) {}
@@ -97,7 +101,7 @@ export class PreviewDiff {
     }
     try {
       const text = await this.oldText(base)
-      const document = text === null ? undefined : await this.readOld(text)
+      const document = text === null ? undefined : await this.oldDocument(text)
       if (request !== this.latest)
         return
       if (text !== null && !document) {
@@ -135,4 +139,17 @@ export class PreviewDiff {
     }
     return this.old.text
   }
+
+  private oldDocument(text: string): Promise<OldDocument | undefined> {
+    const inputs = this.oldInputs()
+    if (this.parsed?.text !== text || this.parsed.inputs !== inputs) {
+      const document = this.readOld(text)
+      this.parsed = { text, inputs, document }
+      document.catch(() => {
+        if (this.parsed?.document === document)
+          this.parsed = undefined
+      })
+    }
+    return this.parsed.document
+  }
 }