fix: path-shim extname (#64)

Author: ota-meshi

.changeset/brown-birds-stare.md

@@ -0,0 +1,5 @@
+---
+"vite-plugin-eslint4b": patch
+---
+
+fix: path-shim extname

shim/path-shim.mjs

@@ -8,7 +8,7 @@ export function basename(p, ext) {
 }
 
 export function extname(p) {
-  return /\.[^.]+$/u.exec(p)[0];
+  return /\.[^.]+$/u.exec(p)?.[0] || "";
 }
 
 export function relative(from, to) {
@@ -43,7 +43,7 @@ export function parse(s) {
     dir,
     base,
     ext,
-    name: basename(ext, ext),
+    name: basename(base, ext),
   };
 }