feat: A flag (--save-metafiles) to save esbuild metafiles

- Useful for analysing bundle size

esbuild/esbuild.js

@@ -60,6 +60,11 @@ const argv = yargs
 		type: "boolean",
 		description: "Run build command for apps",
 	})
+	.option("save-metafiles", {
+		type: "boolean",
+		description:
+			"Saves esbuild metafiles for built assets. Useful for analyzing bundle size. More info: https://esbuild.github.io/api/#metafile",
+	})
 	.example("node esbuild --apps frappe,erpnext", "Run build only for frappe and erpnext")
 	.example(
 		"node esbuild --files frappe/website.bundle.js,frappe/desk.bundle.js",
@@ -401,6 +406,13 @@ async function write_assets_json(metafile) {
 
 	await fs.promises.writeFile(assets_json_path, JSON.stringify(new_assets_json, null, 4));
 	await update_assets_json_in_cache();
+	if (argv["save-metafiles"]) {
+		// use current timestamp in readable formate as a suffix for filename
+		let current_timestamp = new Date().getTime();
+		const metafile_name = `meta-${current_timestamp}.json`;
+		await fs.promises.writeFile(`${metafile_name}`, JSON.stringify(metafile));
+		log(`Saved metafile as ${metafile_name}`);
+	}
 	return {
 		new_assets_json,
 		prev_assets_json,

frappe/build.py

@@ -229,6 +229,7 @@ def bundle(
 	verbose=False,
 	skip_frappe=False,
 	files=None,
+	save_metafiles=False,
 ):
 	"""concat / minify js files"""
 	setup()
@@ -248,6 +249,9 @@ def bundle(
 
 	command += " --run-build-command"
 
+	if save_metafiles:
+		command += " --save-metafiles"
+
 	check_node_executable()
 	frappe_app_path = frappe.get_app_path("frappe", "..")
 	frappe.commands.popen(command, cwd=frappe_app_path, env=get_node_env(), raise_err=True)

frappe/commands/utils.py

@@ -31,6 +31,12 @@ EXTRA_ARGS_CTX = {"ignore_unknown_options": True, "allow_extra_args": True}
 @click.option(
 	"--force", is_flag=True, default=False, help="Force build assets instead of downloading available"
 )
+@click.option(
+	"--save-metafiles",
+	is_flag=True,
+	default=False,
+	help="Saves esbuild metafiles for built assets. Useful for analyzing bundle size. More info: https://esbuild.github.io/api/#metafile",
+)
 def build(
 	app=None,
 	apps=None,
@@ -38,6 +44,7 @@ def build(
 	production=False,
 	verbose=False,
 	force=False,
+	save_metafiles=False,
 ):
 	"Compile JS and CSS source files"
 	from frappe.build import bundle, download_frappe_assets
@@ -62,7 +69,14 @@ def build(
 		if production:
 			mode = "production"
 
-		bundle(mode, apps=apps, hard_link=hard_link, verbose=verbose, skip_frappe=skip_frappe)
+		bundle(
+			mode,
+			apps=apps,
+			hard_link=hard_link,
+			verbose=verbose,
+			skip_frappe=skip_frappe,
+			save_metafiles=save_metafiles,
+		)
 
 
 @click.command("watch")