Hash demo bundle filename to bypass Pages CDN cache

GitHub Pages serves with cache-control: max-age=600 which can't be
overridden. That used to mean every deploy could take up to ten minutes
to become visible to repeat visitors. Naming the rollup entry as
bundle-[hash].js and rewriting examples/index.html to reference the
freshly emitted filename sidesteps the cache entirely — each deploy
yields a different URL for the asset and browsers re-fetch on first
navigation. Also cleans up stale bundle-*.js from previous builds so
docs/ doesn't accrete.

Author: nixel2007

rollup.config.demo.js

@@ -11,14 +11,21 @@ import resolve from "@rollup/plugin-node-resolve"
 import commonjs from "@rollup/plugin-commonjs"
 import terser from "@rollup/plugin-terser"
 import {lezer} from "@lezer/generator/rollup"
-import {copyFileSync, mkdirSync} from "node:fs"
+import {mkdirSync, readFileSync, writeFileSync, readdirSync, rmSync} from "node:fs"
 
 mkdirSync("docs", {recursive: true})
 
+// Pages serves with cache-control: max-age=600, which means browsers and the
+// edge CDN keep serving the same `bundle.js` for ten minutes after a deploy.
+// Naming the entry with a content-hash sidesteps the cache entirely: the
+// HTML always points at the freshly-named asset, so consumers download the
+// new bytes on the first navigation after a deploy.
+
 export default {
   input: "examples/demo.ts",
   output: {
-    file: "docs/bundle.js",
+    dir: "docs",
+    entryFileNames: "bundle-[hash].js",
     format: "iife",
     inlineDynamicImports: true,
     sourcemap: false
@@ -35,9 +42,22 @@ export default {
       compress: {passes: 2}
     }),
     {
-      name: "copy-html-shell",
-      writeBundle() {
-        copyFileSync("examples/index.html", "docs/index.html")
+      name: "html-with-hashed-bundle",
+      // Runs after Rollup decides on chunk names; we pick up the actual
+      // emitted filename and inject it into the HTML shell.
+      writeBundle(_, bundle) {
+        const entry = Object.values(bundle).find(c => c.type === "chunk" && c.isEntry)
+        if (!entry) throw new Error("rollup-plugin html-with-hashed-bundle: no entry chunk")
+        const html = readFileSync("examples/index.html", "utf8")
+          .replace(/\.\/bundle(?:-[^"]+)?\.js/, `./${entry.fileName}`)
+        writeFileSync("docs/index.html", html)
+        // Clean up stale bundle-*.js files from previous builds so we don't
+        // pile them up across rebuilds.
+        for (const f of readdirSync("docs")) {
+          if (/^bundle-.*\.js$/.test(f) && f !== entry.fileName) {
+            rmSync(`docs/${f}`)
+          }
+        }
       }
     }
   ]