[feat] install adapters on demand (sveltejs#7462)

* [feat] install adapters on demand

Closes sveltejs#5123

* oops

* lock file, more logs

* use postinstall hook

* maybe

* ugh

* ignore errors that are not about module not found

* debug

* test node_env findings

* remove dev omit and set node_env through JS

* no env whatsoever?

* this seems to work?

* diy

* tweak copy to mention deployment configuration

Co-authored-by: Rich Harris <[email protected]>

.changeset/orange-geckos-bake.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-auto': patch
+---
+
+[feat] install adapters on demand

packages/adapter-auto/index.js

@@ -1,40 +1,105 @@
+import { execSync } from 'child_process';
+import { pathToFileURL } from 'url';
+import { resolve } from 'import-meta-resolve';
 import { adapters } from './adapters.js';
+import { dirname, join } from 'path';
+import { existsSync } from 'fs';
 
 /** @type {import('./index').default} */
 let fn;
 
+/** @type {Record<string, (name: string) => string>} */
+const commands = {
+	npm: (name) => `npm install -D ${name}`,
+	pnpm: (name) => `pnpm add -D ${name}`,
+	yarn: (name) => `yarn add -D ${name}`
+};
+
+function detect_lockfile() {
+	let dir = process.cwd();
+
+	do {
+		if (existsSync(join(dir, 'pnpm-lock.yaml'))) return 'pnpm';
+		if (existsSync(join(dir, 'yarn.lock'))) return 'yarn';
+		if (existsSync(join(dir, 'package-lock.json'))) return 'npm';
+	} while (dir !== (dir = dirname(dir)));
+
+	return 'npm';
+}
+
+function detect_package_manager() {
+	const manager = detect_lockfile();
+
+	try {
+		execSync(`${manager} --version`);
+		return manager;
+	} catch {
+		return 'npm';
+	}
+}
+
+/** @param {string} name */
+async function import_from_cwd(name) {
+	const cwd = pathToFileURL(process.cwd()).href;
+	const url = await resolve(name, cwd + '/x.js');
+
+	return import(url);
+}
+
 for (const candidate of adapters) {
 	if (candidate.test()) {
 		/** @type {{ default: () => import('@sveltejs/kit').Adapter }} */
 		let module;
 
 		try {
-			module = await import(candidate.module);
-
-			fn = () => {
-				const adapter = module.default();
-				return {
-					...adapter,
-					adapt: (builder) => {
-						builder.log.info(`Detected environment: ${candidate.name}. Using ${candidate.module}`);
-						return adapter.adapt(builder);
-					}
-				};
-			};
-
-			break;
+			module = await import_from_cwd(candidate.module);
 		} catch (error) {
 			if (
 				error.code === 'ERR_MODULE_NOT_FOUND' &&
 				error.message.startsWith(`Cannot find package '${candidate.module}'`)
 			) {
-				throw new Error(
-					`It looks like ${candidate.module} is not installed. Please install it and try building your project again.`
-				);
-			}
+				const package_manager = detect_package_manager();
+				const command = commands[package_manager](candidate.module);
+
+				try {
+					console.log(`Installing ${candidate.module}...`);
+
+					execSync(command, {
+						stdio: 'inherit',
+						env: {
+							...process.env,
+							NODE_ENV: undefined
+						}
+					});
 
-			throw error;
+					module = await import_from_cwd(candidate.module);
+
+					console.log(`Successfully installed ${candidate.module}.`);
+					console.warn(
+						`\nIf you plan on staying on this deployment platform, consider replacing @sveltejs/adapter-auto with ${candidate.module}. This will give you faster and more robust installs, and more control over deployment configuration.\n`
+					);
+				} catch (e) {
+					throw new Error(
+						`Could not install ${candidate.module}. Please install it yourself by adding it to your package.json's devDependencies and try building your project again.`
+					);
+				}
+			} else {
+				throw error;
+			}
 		}
+
+		fn = () => {
+			const adapter = module.default();
+			return {
+				...adapter,
+				adapt: (builder) => {
+					builder.log.info(`Detected environment: ${candidate.name}. Using ${candidate.module}`);
+					return adapter.adapt(builder);
+				}
+			};
+		};
+
+		break;
 	}
 }
 

packages/adapter-auto/package.json

@@ -29,13 +29,11 @@
 		"format": "pnpm lint --write",
 		"check": "tsc"
 	},
-	"dependencies": {
-		"@sveltejs/adapter-cloudflare": "workspace:*",
-		"@sveltejs/adapter-netlify": "workspace:*",
-		"@sveltejs/adapter-vercel": "workspace:*"
-	},
 	"devDependencies": {
 		"@types/node": "^16.11.68",
 		"typescript": "^4.8.4"
+	},
+	"dependencies": {
+		"import-meta-resolve": "^2.1.0"
 	}
 }