perf: avoid splitting every path during file autocomplete (#18919)

config/scripts/mobile-file-ranking-benchmark.mjs

@@ -0,0 +1,53 @@
+import assert from 'node:assert/strict'
+import { execFileSync } from 'node:child_process'
+import { readFileSync } from 'node:fs'
+import { stripTypeScriptTypes } from 'node:module'
+import { performance } from 'node:perf_hooks'
+
+const baseline = process.argv[2]
+if (!baseline) {
+  throw new Error('Usage: node config/scripts/mobile-file-ranking-benchmark.mjs <baseline-ref>')
+}
+async function load(source) {
+  const js = stripTypeScriptTypes(source, { mode: 'transform' })
+  return await import(`data:text/javascript;base64,${Buffer.from(js).toString('base64')}`)
+}
+function measure(fn, paths, query) {
+  for (let warmup = 0; warmup < 10; warmup++) {
+    fn(paths, query, 16)
+  }
+  const samples = []
+  for (let i = 0; i < 9; i++) {
+    const start = performance.now()
+    fn(paths, query, 16)
+    samples.push(performance.now() - start)
+  }
+  return samples.sort((a, b) => a - b)[4]
+}
+const results = []
+for (const [file, name] of [
+  ['src/main/runtime/runtime-mobile-file-path-search.ts', 'rankRuntimeMobileFilePaths'],
+  ['mobile/src/session/mobile-native-chat-autocomplete.ts', 'rankSuggestions']
+]) {
+  const before = (
+    await load(execFileSync('git', ['show', `${baseline}:${file}`], { encoding: 'utf8' }))
+  )[name]
+  const after = (await load(readFileSync(file, 'utf8')))[name]
+  for (const count of [100, 100000]) {
+    const paths = Array.from(
+      { length: count },
+      (_, i) => `src/components/workspace/group-${i % 100}/file-${i}.tsx`
+    )
+    for (const query of ['file-9', 'missing', 'workspace']) {
+      assert.deepEqual(after(paths, query, 16), before(paths, query, 16))
+      results.push({
+        function: name,
+        paths: count,
+        query,
+        beforeMs: measure(before, paths, query),
+        afterMs: measure(after, paths, query)
+      })
+    }
+  }
+}
+console.log(JSON.stringify({ node: process.version, platform: process.platform, results }, null, 2))

mobile/src/session/mobile-native-chat-autocomplete.ts

@@ -81,7 +81,7 @@ export function rankSuggestions(candidates: readonly string[], query: string, li
   const substring: string[] = []
   for (const candidate of candidates) {
     const lower = candidate.toLowerCase()
-    const base = lower.split('/').pop() ?? lower
+    const base = lower.slice(lower.lastIndexOf('/') + 1)
     if (lower.startsWith(q) || base.startsWith(q)) {
       prefix.push(candidate)
     } else if (lower.includes(q)) {

src/main/runtime/runtime-mobile-file-path-search.test.ts

@@ -6,6 +6,37 @@ import {
 } from './runtime-mobile-file-path-search'
 
 describe('rankRuntimeMobileFilePaths', () => {
+  it('preserves basename matching, ordering and total counts for unusual paths', () => {
+    const paths = [
+      '',
+      '/',
+      'a/',
+      'a//b.ts',
+      'b.ts',
+      'B.TS',
+      'a\\b.ts',
+      '界/😀.ts',
+      '.hidden',
+      'a/./b.ts'
+    ]
+    for (const query of ['', ' ', 'b', '.ts', '😀', '/', 'a\\', 'missing']) {
+      for (const limit of [0, 1, 3, 100]) {
+        const q = query.trim().toLowerCase()
+        const prefix = paths.filter((path) => {
+          const lower = path.toLowerCase()
+          return lower.startsWith(q) || (lower.split('/').pop() ?? lower).startsWith(q)
+        })
+        const other = paths.filter(
+          (path) => !prefix.includes(path) && path.toLowerCase().includes(q)
+        )
+        expect(rankRuntimeMobileFilePaths(paths, query, limit)).toEqual({
+          paths: [...prefix, ...other].slice(0, limit),
+          totalCount: prefix.length + other.length
+        })
+      }
+    }
+  })
+
   it('ranks path and basename prefixes before substrings and caps output', () => {
     expect(
       rankRuntimeMobileFilePaths(

src/main/runtime/runtime-mobile-file-path-search.ts

@@ -76,7 +76,7 @@ export function rankRuntimeMobileFilePaths(
   let totalCount = 0
   for (const path of paths) {
     const lower = path.toLowerCase()
-    const basename = lower.split('/').pop() ?? lower
+    const basename = lower.slice(lower.lastIndexOf('/') + 1)
     if (lower.startsWith(normalizedQuery) || basename.startsWith(normalizedQuery)) {
       totalCount++
       if (prefix.length < limit) {