Use Rollup to reduce the npm package to just 3 JS files (#58)

jest.config.js

@@ -23,5 +23,6 @@ module.exports = {
     // Testing error handling is still manual, though.
     // We still get 40-50% coverage at least.
     "./src/commands/Install.ts": ignoreCoverage,
+    "./src/RollupEntry.ts": ignoreCoverage,
   },
 };

package.json

@@ -8,6 +8,7 @@
     "build": "ts-node scripts/Build.ts"
   },
   "devDependencies": {
+    "@rollup/plugin-typescript": "8.2.1",
     "@types/jest": "26.0.23",
     "@types/node": "15.12.2",
     "@types/rimraf": "3.0.0",
@@ -19,6 +20,7 @@
     "jest": "27.0.4",
     "prettier": "2.3.1",
     "rimraf": "3.0.2",
+    "rollup": "2.51.2",
     "ts-jest": "27.0.3",
     "ts-node": "10.0.0",
     "typescript": "4.3.2"

scripts/Build.ts

@@ -1,7 +1,9 @@
-import * as childProcess from "child_process";
+import typescript from "@rollup/plugin-typescript";
 import * as fs from "fs";
+import { builtinModules } from "module";
 import * as path from "path";
 import * as rimraf from "rimraf";
+import { rollup } from "rollup";
 
 const DIR = path.dirname(__dirname);
 const BUILD = path.join(DIR, "build");
@@ -29,40 +31,71 @@ const FILES_TO_COPY: Array<FileToCopy> = [
   { src: "README-npm.md", dest: "README.md" },
 ];
 
-if (fs.existsSync(BUILD)) {
-  rimraf.sync(BUILD);
-}
-
-fs.mkdirSync(BUILD);
-
-for (const { src, dest = src } of FILES_TO_COPY) {
-  fs.copyFileSync(path.join(DIR, src), path.join(BUILD, dest));
-}
-
-childProcess.spawnSync("npx", ["--no-install", "tsc"], {
-  shell: true,
-  stdio: "inherit",
-});
-
 function modifyFile(
   file: string,
   transform: (content: string) => string
 ): void {
   fs.writeFileSync(file, transform(fs.readFileSync(file, "utf8")));
 }
 
-function adjustDefaultExport(content: string): string {
-  return content.replace(/^exports.default =/m, "module.exports =");
-}
+async function run(): Promise<void> {
+  if (fs.existsSync(BUILD)) {
+    rimraf.sync(BUILD);
+  }
 
-modifyFile(path.join(BUILD, "index.js"), adjustDefaultExport);
-modifyFile(path.join(BUILD, "getExecutable.js"), adjustDefaultExport);
-modifyFile(path.join(BUILD, "commands", "Help.js"), (content) =>
-  content.replace(/%VERSION%/g, PKG.version)
-);
+  fs.mkdirSync(BUILD);
 
-fs.chmodSync(path.join(BUILD, "index.js"), "755");
+  for (const { src, dest = src } of FILES_TO_COPY) {
+    fs.copyFileSync(path.join(DIR, src), path.join(BUILD, dest));
+  }
 
-modifyFile(path.join(DIR, "docs", "getting-started.md"), (content) =>
-  content.replace(/("elm-tooling":\s*)"[^"]+"/g, `$1"${PKG.version}"`)
-);
+  const entry = path.join(DIR, "src", "RollupEntry.ts");
+
+  const bundle = await rollup({
+    input: entry,
+    external: builtinModules,
+    plugins: [typescript()],
+    onwarn: (warning) => {
+      // Rollup warnings _do_ have a real `.toString()` method.
+      // eslint-disable-next-line @typescript-eslint/no-base-to-string
+      throw new Error(warning.toString());
+    },
+  });
+
+  const { output } = await bundle.generate({
+    format: "cjs",
+    hoistTransitiveImports: false,
+    chunkFileNames: "[name].js",
+    interop: "esModule",
+  });
+
+  for (const item of output) {
+    switch (item.type) {
+      case "asset":
+        throw new Error(`Unexpectedly got an "asset".`);
+
+      case "chunk":
+        if (item.facadeModuleId !== entry) {
+          const isIndex = item.name === "index";
+          const code = item.code
+            .replace(/%VERSION%/g, PKG.version)
+            .replace(/^exports.default =/m, "module.exports =");
+          const fullCode = isIndex ? `#!/usr/bin/env node\n${code}` : code;
+          fs.writeFileSync(
+            path.join(BUILD, item.fileName),
+            fullCode,
+            isIndex ? { mode: "755" } : {}
+          );
+        }
+    }
+  }
+
+  modifyFile(path.join(DIR, "docs", "getting-started.md"), (content) =>
+    content.replace(/("elm-tooling":\s*)"[^"]+"/g, `$1"${PKG.version}"`)
+  );
+}
+
+run().catch((error: Error) => {
+  process.stderr.write(`${error.message}\n`);
+  process.exit(1);
+});

scripts/tsconfig.json

@@ -2,6 +2,7 @@
   "extends": "../tsconfig.json",
   "exclude": [],
   "compilerOptions": {
-    "noEmit": true
+    "esModuleInterop": true,
+    "module": "CommonJS",
   }
 }

src/RollupEntry.ts

@@ -0,0 +1,12 @@
+/* eslint-disable @typescript-eslint/explicit-function-return-type */
+
+// This file is only used to get Rollup to output the files we want: One file
+// per entrypoint, and one shared file.
+
+export async function index() {
+  return import("./index");
+}
+
+export async function getExecutable() {
+  return import("./getExecutable");
+}

src/index.ts

@@ -1,5 +1,3 @@
-#!/usr/bin/env node
-
 import { help } from "./commands/Help";
 import { init } from "./commands/Init";
 import { install } from "./commands/Install";

tests/tsconfig.json

@@ -2,6 +2,6 @@
   "extends": "../tsconfig.json",
   "exclude": [],
   "compilerOptions": {
-    "noEmit": true
+    "module": "CommonJS",
   }
 }

tsconfig.json

@@ -4,8 +4,9 @@
     "forceConsistentCasingInFileNames": true,
     "importsNotUsedAsValues": "error",
     "isolatedModules": true,
-    "module": "CommonJS",
+    "module": "ESNext",
     "moduleResolution": "node",
+    "noEmit": true,
     "noFallthroughCasesInSwitch": true,
     "noImplicitOverride": true,
     "noImplicitReturns": true,
@@ -18,7 +19,6 @@
     "lib": [
       "ES2018",
     ],
-    "outDir": "build"
   },
   "exclude": [
     "scripts",