Consolidate hydration scripts into just one (withastro#3571)

* Remove redundant hydration scripts

* Prebuild the island JS

* Fix build

* Updates to tests

* Update more references

* Custom element test now has two classic scripts

* Account for non-default exports

* Restructure hydration directives

* Move nested logic into the island component

* Remove try/catch

cmd/prebuild.js

@@ -0,0 +1,52 @@
+import * as terser from 'terser';
+import esbuild from 'esbuild';
+import glob from 'tiny-glob';
+import fs from 'fs';
+import path from 'path';
+import { pathToFileURL, fileURLToPath } from 'url';
+
+export default async function prebuild(...args) {
+	let buildToString = args.indexOf('--to-string');
+	if(buildToString !== -1) {
+		args.splice(buildToString, 1);
+		buildToString = true;
+	}
+
+	let patterns = args;
+	let entryPoints = [].concat(
+		...(await Promise.all(
+			patterns.map((pattern) => glob(pattern, { filesOnly: true, absolute: true }))
+		))
+	);
+
+	function getPrebuildURL(entryfilepath) {
+		const entryURL = pathToFileURL(entryfilepath);
+		const basename = path.basename(entryfilepath);
+		const ext = path.extname(entryfilepath);
+		const name = basename.slice(0, basename.indexOf(ext));
+		const outname = `${name}.prebuilt${ext}`;
+		const outURL = new URL('./' + outname, entryURL);
+		return outURL;
+	}
+
+	async function prebuildFile(filepath) {
+		const tscode = await fs.promises.readFile(filepath, 'utf-8');
+		const esbuildresult = await esbuild.transform(tscode, {
+			loader: 'ts',
+			minify: true
+		});
+		const rootURL = new URL('../../', import.meta.url);
+		const rel = path.relative(fileURLToPath(rootURL), filepath)
+		const mod = `/**
+ * This file is prebuilt from ${rel}
+ * Do not edit this directly, but instead edit that file and rerun the prebuild
+ * to generate this file.
+ */
+
+export default \`${esbuildresult.code.trim()}\`;`;
+		const url = getPrebuildURL(filepath);
+		await fs.promises.writeFile(url, mod, 'utf-8');
+	}
+
+	await Promise.all(entryPoints.map(prebuildFile));
+}

index.js

@@ -13,6 +13,11 @@ export default async function run() {
 			await copy(...args);
 			break;
 		}
+		case 'prebuild': {
+			const { default: prebuild } = await import('./cmd/prebuild.js');
+			await prebuild(...args);
+			break;
+		}
 	}
 }