vweb: add an optional Context.before_accept_loop/0 method, to make testing easier and more robust (#20538)

vlib/vweb/tests/vweb_should_listen_on_both_ipv4_and_ipv6_by_default_test.v

@@ -0,0 +1,120 @@
+import os
+import log
+import time
+import vweb
+import net.http
+
+const vexe = os.getenv('VEXE')
+const vroot = os.dir(vexe)
+const port = 28871
+const welcome_text = 'Welcome to our simple vweb server'
+
+// Use a known good http client like `curl` (if it exists):
+const curl_executable = os.find_abs_path_of_executable('curl') or { '' }
+const curl_ok = curl_supports_ipv6()
+
+fn curl_supports_ipv6() bool {
+	if curl_executable == '' {
+		return false
+	}
+	curl_res := os.execute('${curl_executable} --version')
+	if curl_res.exit_code != 0 {
+		return false
+	}
+	if !curl_res.output.match_glob('curl*Features: * IPv6 *') {
+		return false
+	}
+	return true
+}
+
+fn testsuite_begin() {
+	log.set_level(.debug)
+	log.debug(@FN)
+	os.chdir(vroot) or {}
+	if curl_ok {
+		log.info('working curl_executable found at: ${curl_executable}')
+	} else {
+		log.warn('no working working curl_executable found')
+	}
+	start_services()
+}
+
+fn testsuite_end() {
+	log.debug(@FN)
+}
+
+//
+
+fn ensure_curl_works(tname string) ? {
+	if !curl_ok {
+		log.warn('skipping test ${tname}, since it needs a working curl')
+		return none
+	}
+}
+
+fn test_curl_connecting_through_ipv4_works() {
+	ensure_curl_works(@FN) or { return }
+	res := os.execute('${curl_executable} --connect-timeout 0.5 --silent http://127.0.0.1:${port}/')
+	assert res.exit_code == 0, res.output
+	assert res.output == welcome_text
+	log.info('> ${@FN}')
+}
+
+fn test_net_http_connecting_through_ipv4_works() {
+	res := http.get('http://127.0.0.1:${port}/')!
+	assert res.status_code == 200, res.str()
+	assert res.status_msg == 'OK', res.str()
+	assert res.body == welcome_text, res.str()
+	log.info('> ${@FN}')
+}
+
+fn test_curl_connecting_through_ipv6_works() {
+	ensure_curl_works(@FN) or { return }
+	res := os.execute('${curl_executable} --silent --connect-timeout 0.5 http://[::1]:${port}/')
+	assert res.exit_code == 0, res.output
+	assert res.output == welcome_text
+	log.info('> ${@FN}')
+}
+
+fn test_net_http_connecting_through_ipv6_works() {
+	$if windows {
+		log.warn('skipping test ${@FN} on windows for now')
+		return
+	}
+	res := http.get('http://[::1]:${port}/')!
+	assert res.status_code == 200, res.str()
+	assert res.status_msg == 'OK', res.str()
+	assert res.body == welcome_text, res.str()
+	log.info('> ${@FN}')
+}
+
+//
+
+struct App {
+	vweb.Context
+mut:
+	started chan bool
+}
+
+pub fn (mut app App) before_accept_loop() {
+	app.started <- true
+}
+
+pub fn (mut app App) index() vweb.Result {
+	return app.text(welcome_text)
+}
+
+fn start_services() {
+	log.debug('starting watchdog thread to ensure the test will always exit one way or another...')
+	spawn fn (timeout_in_ms int) {
+		time.sleep(timeout_in_ms * time.millisecond)
+		log.error('Timeout of ${timeout_in_ms} ms reached, for webserver: pid: ${os.getpid()}. Exiting ...')
+		exit(1)
+	}(10_000)
+
+	log.debug('starting webserver...')
+	mut app := &App{}
+	spawn vweb.run(app, port)
+	_ := <-app.started
+	log.debug('webserver started')
+}

vlib/vweb/vweb.v

@@ -204,9 +204,19 @@ pub fn (ctx Context) init_server() {
 	eprintln('init_server() has been deprecated, please init your web app in `fn main()`')
 }
 
+// before_accept_loop is called once the vweb app is started, and listening, but before the loop that accepts
+// incomming request connections.
+// It will be called in the main thread, that runs vweb.run/2 or vweb.run_at/2.
+// It allows you to be notified about the successfull start of your app, and to synchronise your other threads
+// with the webserver start, without error prone and slow pooling or time.sleep waiting.
+// Defining this method is optional.
+pub fn (ctx &Context) before_accept_loop() {
+}
+
+// before_request is called once before each request is routed.
+// It will be called in one of multiple threads in a pool, serving requests,
+// the same one, in which the matching route method will be executed right after it.
 // Defining this method is optional.
-// This method is called before every request (aka middleware).
-// You can use it for checking user session cookies or to add headers.
 pub fn (ctx Context) before_request() {}
 
 // TODO - test
@@ -567,6 +577,10 @@ pub fn run_at[T](global_app &T, params RunParams) ! {
 	}
 	flush_stdout()
 
+	unsafe {
+		global_app.before_accept_loop()
+	}
+
 	// Forever accept every connection that comes, and
 	// pass it through the channel, to the thread pool:
 	for {