⚡ perf(vscode): 查到的定义落到名字上时只读定义那一段，不把目标文件整份取出来

vscode/src/codeReader/editor/definitions.test.ts

@@ -1,10 +1,13 @@
 import { describe, expect, it, vi } from 'vitest'
-import { definitionOffset } from './definitions'
+import { commands, workspace } from 'vscode'
+import { definitionOffset, languageDefinitions } from './definitions'
 
 vi.mock('vscode', () => ({
   commands: { executeCommand: vi.fn() },
   EventEmitter: class EventEmitter { event = vi.fn(); fire = vi.fn() },
-  Range: class Range {},
+  Range: class Range {
+    constructor(readonly start: { offset: number }, readonly end: { offset: number }) {}
+  },
   Uri: { parse: vi.fn() },
   window: { createOutputChannel: vi.fn(() => ({ appendLine: vi.fn(), info: vi.fn(), warn: vi.fn(), error: vi.fn() })) },
   workspace: { openTextDocument: vi.fn(), asRelativePath: vi.fn() },
@@ -40,3 +43,39 @@ describe('定义范围的起点不在名字上时，用范围里那个名字', (
     expect(definitionOffset(text, { start: 0, end: text.length }, undefined, 'fetchAppDeployments')).toBe(text.lastIndexOf('fetchAppDeployments'))
   })
 })
+
+/** 假的文档：位置就是下标；记下 getText 每次取了多长。 */
+function fakeDocument(uri: string, text: string): { reads: number[] } {
+  const reads: number[] = []
+  const at = (offset: number) => ({ offset })
+  const document = {
+    uri: { toString: () => uri },
+    offsetAt: (position: { offset: number }) => position.offset,
+    positionAt: (offset: number) => at(Math.max(0, Math.min(offset, text.length))),
+    getText: (range?: { start: { offset: number }, end: { offset: number } }) => {
+      const read = range ? text.slice(range.start.offset, range.end.offset) : text
+      reads.push(read.length)
+      return read
+    },
+    getWordRangeAtPosition: (position: { offset: number }) => {
+      const start = text.slice(0, position.offset).search(/\w+$/)
+      const end = position.offset + (/^\w*/.exec(text.slice(position.offset))?.[0].length ?? 0)
+      return { start: at(start < 0 ? position.offset : start), end: at(end) }
+    },
+  }
+  vi.mocked(workspace.openTextDocument).mockImplementation((async (target: { toString: () => string }) => target.toString() === uri ? document : undefined) as never)
+  return { reads }
+}
+
+describe('查到的定义落到名字上', () => {
+  it('只读定义那一段（前后各多一个字认名字的边界），不把目标文件整份取出来', async () => {
+    const text = `${'# 很长的文件\n'.repeat(2000)}def fetch_app(x):\n    return fetch_app(x)\n`
+    const { reads } = fakeDocument('file:///w/a.py', text)
+    const call = text.lastIndexOf('fetch_app')
+    const declaration = text.indexOf('def fetch_app')
+    vi.mocked(commands.executeCommand).mockResolvedValue([{ uri: { toString: () => 'file:///w/a.py' }, range: { start: { offset: declaration }, end: { offset: text.indexOf(':', declaration) } } }] as never)
+    const [found] = await languageDefinitions({ toString: () => 'file:///w/a.py' } as never, { offset: call } as never)
+    expect((found.range.start as unknown as { offset: number }).offset).toBe(text.indexOf('fetch_app', declaration))
+    expect(Math.max(...reads)).toBeLessThan(40)
+  })
+})

vscode/src/codeReader/editor/definitions.ts

@@ -108,16 +108,22 @@ async function rangeOnName(uri: Uri, range: Range, selection: Range | undefined,
     return fallback
   try {
     const document = await workspace.openTextDocument(uri)
-    const text = document.getText()
+    const start = document.offsetAt(range.start)
+    const end = document.offsetAt(range.end)
+    const selected = selection && { start: document.offsetAt(selection.start), end: document.offsetAt(selection.end) }
+    // 只取定义这一段，前后各多一个字（认名字的边界）：目标文件可能很大，每处定义都整份取一遍太费
+    const from = Math.max(0, Math.min(start, selected?.start ?? start) - 1)
+    const to = Math.max(end, (selected?.start ?? start) + name.length) + 1
+    const text = document.getText(new Range(document.positionAt(from), document.positionAt(to)))
     const offset = definitionOffset(
       text,
-      { start: document.offsetAt(range.start), end: document.offsetAt(range.end) },
+      { start: start - from, end: end - from },
-      selection ? { start: document.offsetAt(selection.start), end: document.offsetAt(selection.end) } : undefined,
+      selected && { start: selected.start - from, end: selected.end - from },
       name,
     )
     if (!onName(text, offset, name))
       return fallback
-    return new Range(document.positionAt(offset), document.positionAt(offset + name.length))
+    return new Range(document.positionAt(from + offset), document.positionAt(from + offset + name.length))
   }
   catch (err) {
     logger.add({ level: 'warn', source: 'codeReader', message: `读不到定义所在的 ${uri.toString()}：${err instanceof Error ? err.message : String(err)}` })