perf: preprocess markdown transform at build time

scripts/build-safari-15.js

@@ -16,6 +16,7 @@
 
 import { build } from "vite";
 import { svelte } from "@sveltejs/vite-plugin-svelte";
+import pluginMarkedDivest from "./vite-plugin-marked-divest.js";
 import * as Utils from "./utils.js";
 
 /** @type {import("vite").InlineConfig} */
@@ -36,7 +37,7 @@ const sharedConfig = {
  */
 build({
 	...Utils.baseConfig,
-	plugins: [svelte()],
+	plugins: [svelte(), pluginMarkedDivest()],
 	build: {
 		...sharedConfig.build,
 		outDir: `${Utils.APP_SHARED_RESOURCES}/dist/`,

scripts/build-safari-16.4.js

@@ -15,6 +15,7 @@
 
 import { build } from "vite";
 import { svelte } from "@sveltejs/vite-plugin-svelte";
+import pluginMarkedDivest from "./vite-plugin-marked-divest.js";
 import * as Utils from "./utils.js";
 
 /** @type {import("vite").InlineConfig} */
@@ -35,7 +36,7 @@ const sharedConfig = {
  */
 build({
 	...Utils.baseConfig,
-	plugins: [svelte()],
+	plugins: [svelte(), pluginMarkedDivest()],
 	build: {
 		...sharedConfig.build,
 		outDir: `${Utils.APP_SHARED_RESOURCES}/dist/`,

scripts/vite-plugin-marked-divest.js

@@ -0,0 +1,89 @@
+import { fileURLToPath } from "node:url";
+import { readFile } from "node:fs/promises";
+import { marked } from "marked";
+
+/**
+ * Exclude files that do not need to be processed
+ * @param {string} id
+ * @returns {boolean}
+ */
+function isExclude(id) {
+	const res = [/\/src\/app\/_locales\/[A-Za-z0-9_]+\/messages\.js/];
+	for (const re of res) {
+		if (re.test(id)) return false;
+	}
+	return true;
+}
+
+/**
+ * Preprocess `marked` calls and `.md?raw` transformations at build time
+ * to avoid including `marked` modules and runtime transformations
+ * @returns {import('vite').Plugin}
+ */
+function preprocessMarked() {
+	return {
+		name: "preprocess-marked",
+		resolveId: {
+			order: "pre",
+			handler(source, importer) {
+				if (isExclude(importer)) return;
+				if (source.endsWith(".md?raw")) {
+					const importerUrl = new URL(importer, import.meta.url);
+					const sourceUrl = new URL(source, importerUrl);
+					return fileURLToPath(sourceUrl) + "?marked";
+				}
+			},
+		},
+		load: {
+			order: "pre",
+			async handler(id) {
+				if (!id.endsWith(".md?marked")) return;
+				const url = new URL(id, import.meta.url);
+				const text = await readFile(fileURLToPath(url), "utf8");
+				const html = await marked.parse(text);
+				return `export default ${JSON.stringify(html)}`;
+			},
+		},
+		transform(code, id) {
+			if (isExclude(id)) return;
+			if (!code.includes("marked.parse")) return;
+			const node = this.parse(code);
+			if (node.sourceType !== "module") return;
+			for (const module of node.body) {
+				if (module.type !== "ImportDeclaration") continue;
+				if (!module.source.value.toString().endsWith(".md?raw")) continue;
+				const specifier = module.specifiers.find(
+					(specifier) => specifier.type === "ImportDefaultSpecifier",
+				);
+				const varName = specifier.local.name;
+				code = code.replace(`await marked.parse(${varName})`, varName);
+				// console.debug(`optimizing 'await marked.parse(${varName})'`, id); // DEBUG
+			}
+			return { code };
+		},
+	};
+}
+
+/**
+ * Turn off `Marked` module side effects for better tree-shaking
+ * @returns {import('vite').Plugin}
+ */
+function disableMarkedSideEffects() {
+	return {
+		name: "disable-marked-side-effects",
+		transform(code, id) {
+			if (id.includes("/node_modules/marked")) {
+				return { code, moduleSideEffects: false };
+			}
+		},
+	};
+}
+
+/**
+ * @returns {import('vite').Plugin[]}
+ */
+function markedDivest() {
+	return [disableMarkedSideEffects(), preprocessMarked()];
+}
+
+export default markedDivest;

src/app/i18n.js

@@ -14,7 +14,6 @@ function getLangFrom(messages, messageName, substitutions = undefined) {
 		console.warn(`i18n - "${messageName}" not found`, messages);
 		return "";
 	}
-	/** @type {string} message */
 	let text = messages[messageName].message;
 	// handle substitutions
 	if (typeof substitutions === "string") {