Report error if optional package is required and missing

Author: pipe01

src/html.ts

@@ -1,6 +1,7 @@
 import { BuildResult } from "esbuild";
 import * as fs from "fs";
 import * as path from "path";
+import { tryAsync as tryImport } from "./utils";
 
 export type IndexOptions = {
     /**
@@ -49,7 +50,7 @@ export async function generateIndexHTML(result: BuildResult, opts: IndexOptions,
         throw new Error("No outFile was specified and it could not be inferred from the build options");
     }
 
-    const cheerio = await import("cheerio");
+    const cheerio = await tryImport(() => import("cheerio"), "cheerio", "HTML generation");
 
     const $ = cheerio.load(await fs.promises.readFile(opts.originalFile));
 
@@ -88,8 +89,8 @@ export async function generateIndexHTML(result: BuildResult, opts: IndexOptions,
     let html = $.html();
 
     if (min) {
-        const { minify } = await import("html-minifier")
-        
+        const { minify } = await tryImport(() => import("html-minifier"), "html-minifier", "HTML minification")
+
         html = minify(html, {
             collapseWhitespace: true,
             minifyCSS: true,

src/index.ts

@@ -6,7 +6,7 @@ import * as crypto from "crypto";
 import * as sfc from '@vue/compiler-sfc';
 
 import { loadRules, replaceRules } from "./paths";
-import { fileExists, getFullPath, getUrlParams } from "./utils"
+import { fileExists, getFullPath, getUrlParams, tryAsync } from "./utils"
 import { Options } from "./options";
 import { generateIndexHTML } from "./html";
 
@@ -135,7 +135,8 @@ const vuePlugin = (opts: Options = {}) => <esbuild.Plugin>{
             let source = descriptor.template.content;
 
             if (descriptor.template.lang === "pug") {
-                source = (await import("pug")).render(descriptor.template.content);
+                const pug = await tryAsync(() => import("pug"), "pug", "Pug template rendering")
+                source = pug.render(descriptor.template.content);
 
                 // Fix #default="#default" and v-else="v-else"
                 source = source.replace(/(\B#.*?|\bv-.*?)="\1"/g, "$1");
@@ -163,8 +164,8 @@ const vuePlugin = (opts: Options = {}) => <esbuild.Plugin>{
             let includedFiles: string[] = [];
 
             if (style.lang === "sass" || style.lang === "scss") {
-                const sass = await import("sass");
-                
+                const sass = await tryAsync(() => import("sass"), "sass", "SASS style preprocessing");
+
                 const result: import("sass").Result = await new Promise((resolve, reject) => sass.render({
                     data: source,
                     indentedSyntax: style.lang === "sass",

src/utils.ts

@@ -22,3 +22,11 @@ export async function fileExists(path: fs.PathLike) {
 export function getFullPath(args: OnResolveArgs) {
     return path.isAbsolute(args.path) ? args.path : path.join(args.resolveDir, args.path);
 }
+
+export async function tryAsync<T>(fn: () => Promise<T>, module: string, requiredFor: string) {
+    try {
+        return await fn();
+    } catch (err) {
+        throw new Error(`Package "${module}" is required for ${requiredFor}. Please run "npm i -D ${module}" and try again.`);
+    }
+}