fix(lint): fix single char selectors being ignored (#27576)

The selector splitting code that's used for JS linting plugins didn't
properly account for selectors being a single character. This can happen
in the case of `*`.

Instead of comparing against the length, we'll now check if the
remaining string portion is not empty, which is more robust. It also
allows us to detect trailing whitespace, which we didn't before.

cli/js/40_lint_selector.js

@@ -406,8 +406,9 @@ export function splitSelectors(input) {
     }
   }
 
-  if (last < input.length - 1) {
-    out.push(input.slice(last).trim());
+  const remaining = input.slice(last).trim();
+  if (remaining.length > 0) {
+    out.push(remaining);
   }
 
   return out;

tests/unit/lint_selectors_test.ts

@@ -20,6 +20,9 @@ import {
 import { assertThrows } from "@std/assert";
 
 Deno.test("splitSelectors", () => {
+  assertEquals(splitSelectors("*"), ["*"]);
+  assertEquals(splitSelectors("*,*"), ["*", "*"]);
+  assertEquals(splitSelectors("*,*     "), ["*", "*"]);
   assertEquals(splitSelectors("foo"), ["foo"]);
   assertEquals(splitSelectors("foo, bar"), ["foo", "bar"]);
   assertEquals(splitSelectors("foo:f(bar, baz)"), ["foo:f(bar, baz)"]);