feat(core): improve @file autocomplete to prioritize filenames (#21064)

packages/core/src/utils/filesearch/fileSearch.ts

@@ -13,6 +13,44 @@ import { AsyncFzf, type FzfResultItem } from 'fzf';
 import { unescapePath } from '../paths.js';
 import type { FileDiscoveryService } from '../../services/fileDiscoveryService.js';
 
+// Tiebreaker: Prefers shorter paths.
+const byLengthAsc = (a: { item: string }, b: { item: string }) =>
+  a.item.length - b.item.length;
+
+// Tiebreaker: Prefers matches at the start of the filename (basename prefix).
+const byBasenamePrefix = (
+  a: { item: string; positions: Set<number> },
+  b: { item: string; positions: Set<number> },
+) => {
+  const getBasenameStart = (p: string) => {
+    const trimmed = p.endsWith('/') ? p.slice(0, -1) : p;
+    return Math.max(trimmed.lastIndexOf('/'), trimmed.lastIndexOf('\\')) + 1;
+  };
+  const aDiff = Math.min(...a.positions) - getBasenameStart(a.item);
+  const bDiff = Math.min(...b.positions) - getBasenameStart(b.item);
+
+  const aIsFilenameMatch = aDiff >= 0;
+  const bIsFilenameMatch = bDiff >= 0;
+
+  if (aIsFilenameMatch && !bIsFilenameMatch) return -1;
+  if (!aIsFilenameMatch && bIsFilenameMatch) return 1;
+  if (aIsFilenameMatch && bIsFilenameMatch) return aDiff - bDiff;
+
+  return 0; // Both are directory matches, let subsequent tiebreakers decide.
+};
+
+// Tiebreaker: Prefers matches closer to the end of the path.
+const byMatchPosFromEnd = (
+  a: { item: string; positions: Set<number> },
+  b: { item: string; positions: Set<number> },
+) => {
+  const maxPosA = Math.max(-1, ...a.positions);
+  const maxPosB = Math.max(-1, ...b.positions);
+  const distA = a.item.length - maxPosA;
+  const distB = b.item.length - maxPosB;
+  return distA - distB;
+};
+
 export interface FileSearchOptions {
   projectRoot: string;
   ignoreDirs: string[];
@@ -192,6 +230,8 @@ class RecursiveFileSearch implements FileSearch {
       // files, because the v2 algorithm is just too slow in those cases.
       this.fzf = new AsyncFzf(this.allFiles, {
         fuzzy: this.allFiles.length > 20000 ? 'v1' : 'v2',
+        forward: false,
+        tiebreakers: [byBasenamePrefix, byMatchPosFromEnd, byLengthAsc],
       });
     }
   }