feat(publish): watch mode

README.md

@@ -122,7 +122,17 @@ _Publish mode_ helps replicate the production environment in your development se
 	Any changes you make to the _Dependency package_ will be reflected in the `node_modules` directory of the _Consuming package_.
 
 	> **Note:** If the _Dependency package_ emits new files, you'll need to re-run `npx link publish <dependency-package-path>` to create new hard links.
-
+
+#### Watch mode
+
+To automatically re-link a package in publish mode whenever a change is made, use the `--watch` flag:
+
+```sh
+npx link publish --watch <dependency-package-path>
+```
+
+Hard links do not support directories, so files must be individually linked. Watch mode addresses this limitation by automatically linking new files added to the _Dependency package_ so they appear in the _Consuming package_.
+
 ### Configuration file
 
 Create a `link.config.json` (or `link.config.js`) configuration file at the root of the _Consuming package_ to automatically setup links to multiple _Dependency packages_.

package.json

@@ -29,6 +29,7 @@
 	},
 	"devDependencies": {
 		"@types/cmd-shim": "^5.0.2",
+		"@types/glob-to-regexp": "^0.4.4",
 		"@types/node": "^20.14.14",
 		"@types/npm-packlist": "^7.0.3",
 		"@types/npmcli__package-json": "^4.0.4",
@@ -38,12 +39,14 @@
 		"execa": "^8.0.1",
 		"fs-fixture": "^2.4.0",
 		"get-node": "^15.0.1",
+		"glob-to-regexp": "^0.4.1",
 		"kolorist": "^1.8.0",
 		"lintroll": "^1.7.1",
 		"manten": "^1.3.0",
 		"npm-packlist": "^8.0.2",
 		"outdent": "^0.8.0",
 		"pkgroll": "^2.4.2",
+		"throttleit": "^2.1.0",
 		"tsx": "^4.16.5",
 		"typescript": "^5.5.4"
 	}

src/cli.ts

@@ -77,7 +77,11 @@ import { publishCommand, publishHandler } from './commands/publish/index.js';
 			},
 		);
 	} else if (argv.command === 'publish') {
-		await publishHandler(cwdProjectPath, argv._);
+		await publishHandler(
+			cwdProjectPath,
+			argv._,
+			argv.flags,
+		);
 	}
 })().catch((error) => {
 	console.error('Error:', error.message);

src/commands/publish/hardlink-package.ts

@@ -10,6 +10,10 @@ export const hardlinkPackage = async (
 	linkPath: string,
 	absoluteLinkPackagePath: string,
 	packageJson: PackageJsonWithName,
+	publishFilesPromise: string[] | Promise<string[]> = getNpmPacklist(
+		absoluteLinkPackagePath,
+		packageJson,
+	),
 ) => {
 	const [oldPublishFiles, publishFiles] = await Promise.all([
 		getNpmPacklist(
@@ -21,10 +25,7 @@ export const hardlinkPackage = async (
 			 */
 			packageJson,
 		),
-		getNpmPacklist(
-			absoluteLinkPackagePath,
-			packageJson,
-		),
+		publishFilesPromise,
 	]);
 
 	console.log(`Linking ${magenta(packageJson.name)} in publish mode:`);

src/commands/publish/index.ts

@@ -5,11 +5,11 @@ export const publishCommand = command({
 	name: 'publish',
 	parameters: ['<package paths...>'],
 	flags: {
-		// watch: {
-		// 	type: Boolean,
-		// 	alias: 'w',
-		// 	description: 'Watch for changes in the package and automatically relink',
-		// },
+		watch: {
+			type: Boolean,
+			alias: 'w',
+			description: 'Watch for changes in the package and automatically relink',
+		},
 	},
 	help: {
 		description: 'Link a package to simulate an environment similar to `npm install`',
@@ -19,13 +19,15 @@ export const publishCommand = command({
 export const publishHandler = async (
 	cwdProjectPath: string,
 	packagePaths: string[],
+	flags: { watch?: boolean },
 ) => {
 	if (packagePaths.length > 0) {
 		await Promise.all(
 			packagePaths.map(
 				linkPackagePath => linkPublishMode(
 					cwdProjectPath,
 					linkPackagePath,
+					flags.watch,
 				),
 			),
 		);

src/commands/publish/link-publish-mode.ts

@@ -1,8 +1,15 @@
-import path from 'path';
-import fs from 'fs/promises';
+import path from 'node:path';
+import fs from 'node:fs/promises';
 import outdent from 'outdent';
-import { magenta, bold, dim } from 'kolorist';
+import throttle from 'throttleit';
+import globToRegexp from 'glob-to-regexp';
+import {
+	magenta, cyan, bold, dim, yellow,
+} from 'kolorist';
 import { readPackageJson } from '../../utils/read-package-json.js';
+import { getNpmPacklist } from '../../utils/get-npm-packlist.js';
+import { cwdPath } from '../../utils/cwd-path.js';
+import { getPrettyTime } from '../../utils/get-pretty-time.js';
 import { hardlinkPackage } from './hardlink-package.js';
 
 const isValidSetup = async (
@@ -27,6 +34,7 @@ const isValidSetup = async (
 export const linkPublishMode = async (
 	basePackagePath: string,
 	linkPackagePath: string,
+	watchMode?: boolean,
 ) => {
 	const absoluteLinkPackagePath = path.resolve(basePackagePath, linkPackagePath);
 	const packageJson = await readPackageJson(absoluteLinkPackagePath);
@@ -54,20 +62,68 @@ export const linkPublishMode = async (
 		return;
 	}
 
-	/**
-	 * If it's a symlink, make sure it's in the node_modules directory of the base package.
-	 * e.g. This could happen with pnpm
-	 *
-	 * If it's not, it might be a development directory and we don't want to overwrite it.
-	 */
-	const linkPathReal = await fs.realpath(linkPath);
-	if (!linkPathReal.startsWith(expectedPrefix)) {
-		return;
-	}
-
-	await hardlinkPackage(
+	const throttledHardlinkPackage = throttle(hardlinkPackage, 500);
+	await throttledHardlinkPackage(
 		linkPath,
 		absoluteLinkPackagePath,
 		packageJson,
 	);
+
+	if (watchMode) {
+		const globOptions = {
+			globstar: true,
+			extended: true,
+		};
+
+		/**
+		 * npm-packlist ignore list:
+		 * https://github.com/npm/npm-packlist/blob/v8.0.2/lib/index.js#L15-L38
+		 */
+		const ignoreFiles = [
+			// Files
+			'**/{npm-debug.log,*.orig,package-lock.json,yarn.lock,pnpm-lock.yaml}',
+
+			// Folders
+			'**/node_modules/**',
+
+			// Hidden files
+			'**/.{_*,*.swp,DS_Store,gitignore,npmrc,npmignore,lock-wscript,.wafpickle-*}',
+
+			// Hidden folders
+			'**/.{_*,git,svn,hg,CVS}/**',
+		].map(glob => globToRegexp(glob, globOptions));
+
+		const watcher = fs.watch(
+			absoluteLinkPackagePath,
+			{ recursive: true },
+		);
+
+		for await (const { eventType, filename } of watcher) {
+			if (!filename) {
+				continue;
+			}
+
+			const shouldIgnore = ignoreFiles.some(ignoreFile => ignoreFile.test(filename));
+			if (shouldIgnore) {
+				continue;
+			}
+
+			const publishFiles = await getNpmPacklist(
+				absoluteLinkPackagePath,
+				packageJson,
+			);
+
+			if (!publishFiles.includes(filename)) {
+				continue;
+			}
+
+			console.log(`\n${dim(getPrettyTime())}`, 'Detected', yellow(eventType), 'in', `${cyan(cwdPath(path.join(absoluteLinkPackagePath, filename)))}\n`);
+			await throttledHardlinkPackage(
+				linkPath,
+				absoluteLinkPackagePath,
+				packageJson,
+				publishFiles,
+			);
+		}
+	}
 };

src/utils/get-pretty-time.ts

@@ -0,0 +1,9 @@
+export const getPrettyTime = () => (new Date()).toLocaleTimeString(
+	undefined,
+	{
+		hour: 'numeric',
+		minute: 'numeric',
+		second: 'numeric',
+		hour12: true,
+	},
+);

tests/specs/publish.spec.ts

@@ -4,18 +4,20 @@ import { testSuite, expect } from 'manten';
 import { execa } from 'execa';
 import { createFixture } from 'fs-fixture';
 import { link } from '../utils/link.js';
+import { streamWaitFor } from '../utils/stream-wait-for.js';
 import { npmPack } from '../utils/npm-pack.js';
 
 export default testSuite(({ describe }, nodePath: string) => {
-	describe('publish mode', ({ test }) => {
-		test('hard links', async () => {
-			await using fixture = await createFixture('./tests/fixtures/');
+	describe('publish mode', async ({ test }) => {
+		await using fixture = await createFixture('./tests/fixtures/');
 
-			const packageFilesPath = fixture.getPath('package-files');
-			const statOriginalFile = await fs.stat(fixture.getPath('package-files/package.json'));
-			const tarballPath = await npmPack(packageFilesPath);
-			const entryPackagePath = fixture.getPath('package-entry');
+		// Prepare tarball to install
+		const packageFilesPath = fixture.getPath('package-files');
+		const statOriginalFile = await fs.stat(fixture.getPath('package-files/package.json'));
+		const tarballPath = await npmPack(packageFilesPath);
+		const entryPackagePath = fixture.getPath('package-entry');
 
+		await test('hard links', async () => {
 			await execa('npm', [
 				'install',
 				'--no-save',
@@ -40,5 +42,34 @@ export default testSuite(({ describe }, nodePath: string) => {
 			const statAfterLink = await fs.stat(path.join(entryPackagePath, 'node_modules/package-files/package.json'));
 			expect(statAfterLink.ino).toBe(statOriginalFile.ino);
 		});
+
+		await test('watch mode', async () => {
+			const watchMode = link([
+				'publish',
+				'--watch',
+				packageFilesPath,
+			], {
+				cwd: entryPackagePath,
+				nodePath,
+			});
+
+			// Wait for initial hardlink
+			await streamWaitFor(watchMode.stdout!, '✔');
+
+			// Should trigger watch because lib is in files
+			fixture.writeFile('package-files/lib/file-a.js', 'file-a');
+			await streamWaitFor(watchMode.stdout!, 'lib/file-a.js');
+
+			// Should not trigger watch because it's not in lib
+			await fixture.writeFile('package-files/file-b.js', 'file-b');
+			await expect(
+				() => streamWaitFor(watchMode.stdout!, 'file-b.js', 1000),
+			).rejects.toThrow('Timeout');
+
+			watchMode.kill();
+			await watchMode;
+		}, {
+			timeout: 5000,
+		});
 	});
 });