esbuild.serve does not emit any URLs / ports, even with logLevel: 'info'

[fregante]

The ClI works

❯ npx esbuild --serve --bundle index.js --outdir=a

 > Local:   http://127.0.0.1:8000/
 > Network: http://10.9.8.45:8000/

The API doesn't output anything:

❯ WATCH=true node esbuild.config.mjs
// nothing

//esbuild.config.mjs
import process from 'node:process';
import esbuild from 'esbuild';

const serve = {
	servedir: 'public',
};
const build = {
	entryPoints: ['index.js'],
	outdir: 'public',
	logLevel: 'info',
};

if (process.env.WATCH === 'true') {
	await esbuild.serve(serve, build);
} else {
	await esbuild.build(build);
}

Any config to make it work? Or is this functionality missing?

[evanw]

The CLI just calls the public API like you are doing, and then pretty-prints the returned address and port:

esbuild/pkg/cli/cli_impl.go

Lines 1320 to 1355 in f730c03

	// If this is "0.0.0.0" or "::", list all relevant IP addresses
	if ip := net.ParseIP(result.Host); ip != nil && ip.IsUnspecified() {
	if addrs, err := net.InterfaceAddrs(); err == nil {
	for _, addr := range addrs {
	if addr, ok := addr.(*net.IPNet); ok && (addr.IP.To4() != nil) == (ip.To4() != nil) && !addr.IP.IsLinkLocalUnicast() {
	hosts = append(hosts, addr.IP.String())
	}
	}
	}
	}
	// Otherwise, just list the one IP address
	if len(hosts) == 0 {
	hosts = append(hosts, result.Host)
	}
	// Determine the host kinds
	kinds := make([]string, len(hosts))
	maxLen := 0
	for i, host := range hosts {
	kind := "Network"
	if ip := net.ParseIP(host); ip != nil && ip.IsLoopback() {
	kind = "Local"
	}
	kinds[i] = kind
	if len(kind) > maxLen {
	maxLen = len(kind)
	}
	}
	// Pretty-print the host list
	for i, kind := range kinds {
	sb.WriteString(fmt.Sprintf("\n > %s:%s %shttp://%s/%s",
	kind, strings.Repeat(" ", maxLen-len(kind)), colors.Underline,
	net.JoinHostPort(hosts[i], fmt.Sprintf("%d", result.Port)), colors.Reset))
	}

You are welcome to print it yourself if you'd like, using whatever formatting you want. The host and port are returned from serve here:

esbuild/lib/shared/types.ts

Lines 238 to 244 in f730c03

	/** Documentation: https://esbuild.github.io/api/#serve-return-values */
	export interface ServeResult {
	port: number;
	host: string;
	wait: Promise<void>;
	stop: () => void;
	}

This is documented here: https://esbuild.github.io/api/#serve-return-values

[fregante]

Thank you for the solution, but that feels like I’m rewriting core functionality and it’s not super straightforward either https://thewebdev.info/2022/02/26/how-to-get-local-ip-address-in-node-js/