feat: only offer a Less alpha that ships the browser bundle

src/components/Header.vue

@@ -1,10 +1,13 @@
 <script setup lang="ts">
 import axios from "axios";
+import { atLeast } from "../options";
 import Select from "./Select.vue";
 const props = defineProps(["store"]);
 const { store } = props;
 
 const baseVersionUrl = "https://cdn.jsdelivr.net/npm/less@";
+// First Less alpha whose npm package includes dist/less-browser-dev.js.
+const MIN_BROWSER_BUNDLE_ALPHA = "5.0.0-alpha.3";
 let activeVersion = $ref("");
 let publishedVersions = $ref<string[]>();
 let showTipFlag = $ref(false);
@@ -40,10 +43,11 @@ async function fetchVersions() {
   });
   // Opt-in: surface the latest v5 alpha (npm `alpha` dist-tag). It loads the
   // dev browser bundle (dist/less-browser-dev.js, window.less) — see fetchLess.
-  // Alphas published before that file existed will 404 and show the load tip.
+  // Like the Less benchmark runner's per-file minimum versions, only offer an
+  // alpha that actually ships that file; older alphas would just 404.
   // Kept out of the default so stable (`latest`) stays the landing version.
   const alpha = data.tags?.alpha;
-  if (alpha && !publishedVersions.includes(alpha)) {
+  if (alpha && atLeast(alpha, MIN_BROWSER_BUNDLE_ALPHA) && !publishedVersions.includes(alpha)) {
     publishedVersions.unshift(alpha);
   }
   // Default to the npm `latest` dist-tag (stable, currently 4.x), never a prerelease.

src/options.ts

@@ -40,10 +40,11 @@ const all: OptionDescriptor[] = [
 ]
 
 // Numeric core only: "5.0.0-alpha.2" compares as 5.0.0; "4.x" as 4.0.0.
+// (Option gates are keyed on the release line, so an alpha counts as its release.)
 const parse = (v: string) =>
   v.split('-')[0].split('.').map(p => Number(p) || 0)
 
-const compare = (a: string, b: string) => {
+export const compare = (a: string, b: string) => {
   const [x, y] = [parse(a), parse(b)]
   for (let i = 0; i < 3; i++) {
     if ((x[i] ?? 0) !== (y[i] ?? 0)) return (x[i] ?? 0) - (y[i] ?? 0)
@@ -60,3 +61,11 @@ export const supportedOptions = (version: string) =>
 // The only object that reaches less.render: valid keys for `version`, nothing else.
 export const renderOptions = (store: OptionStore, version: string) =>
   Object.fromEntries(supportedOptions(version).map(o => [o.key, store[o.key]]))
+
+// Prerelease-aware: same numeric core, then the prerelease number
+// ("5.0.0-alpha.3" >= "5.0.0-alpha.3"; "5.0.0-alpha.2" < "5.0.0-alpha.3").
+const prereleaseNumber = (v: string) => v.includes('-') ? Number(v.split('-')[1].split('.').pop()) || 0 : Infinity
+export const atLeast = (v: string, min: string) => {
+  const core = compare(v, min)
+  return core !== 0 ? core > 0 : prereleaseNumber(v) >= prereleaseNumber(min)
+}