live: make live_test.v more robust

vlib/v/tests/live_test.v

@@ -1,36 +1,111 @@
 import os
 import time
 
+/*
+The goal of this test, is to simulate a developer, that has run a program, compiled with -live flag.
+
+It does so by writing a new generated program containing a [live] fn pmessage() string {...} function,
+then runs the generated program at the start *in the background*, 
+waits some time, so that the program could run a few iterations, then modifies its source 
+(simulates a developer that has saved a new version of the program source), 
+then it waits some more, modifies it again and saves it once more.
+
+On each modification, the running program, should detect that its source code has changed, 
+and recompile a shared library, which it then it should load, and thus modify its own 
+behavior at runtime (the pmessage function).
+
+If everything works fine, the output of the generated program would have changed at least 1-2 times,
+which then is detected by the test program (the histogram checks).
+
+Since this test program is sensitive to coordination (or lack of) of several processes, 
+it tries to sidestep the coordination issue by polling the file system for the existance 
+of files, ORIGINAL.txt ... STOP.txt , which are appended to by the generated program.
+
+NB: That approach of monitoring the state of the running generated program, is clearly not ideal, 
+but sidesteps the issue of coordinating processes through IPC or stdin/stdout in hopefully 
+not very flaky way.
+
+TODO: Cleanup this when/if v has better process control/communication primitives.
+*/
+
 const (
 	vexe                = os.getenv('VEXE')
+	tmp_file            = os.join_path(os.temp_dir(), 'generated_live_program.tmp.v')
 	source_file         = os.join_path(os.temp_dir(), 'generated_live_program.v')
+	genexe_file         = os.join_path(os.temp_dir(), 'generated_live_program')
 	output_file         = os.join_path(os.temp_dir(), 'generated_live_program.output.txt')
+	res_original_file   = os.join_path(os.temp_dir(), 'ORIGINAL.txt')
+	res_changed_file    = os.join_path(os.temp_dir(), 'CHANGED.txt')
+	res_another_file    = os.join_path(os.temp_dir(), 'ANOTHER.txt')
+	res_stop_file       = os.join_path(os.temp_dir(), 'STOP.txt')
 	live_program_source = "
 module main
-import time
 
-[live]
-fn pmessage() {
-	println('ORIGINAL')
+import time
+import os
+import live
+
+fn append_to_file(fname, s string) {
+	f := os.open_append(fname) or {
+		println('>>>> could not open file \$fname for appending, err: \$err ')
+		return 
+	}
+	f.writeln('\$s')
+	//info := live.info()    
+	//f.writeln('>>> reloads: \${info.reloads} | ok reloads: \${info.reloads_ok}')
+	f.flush()
+	f.close()
+}    
+
+fn myprintln(s string) {
+	append_to_file('$output_file', s)
+	println(s)
+	os.flush()
 }
 
+[live]
+fn pmessage() string {
+	s := 'ORIGINAL'
+	myprintln(s)
+	return s
+}
+
+const (
+	delay = 5
+)
+
 fn main() {
-	println('START')
+	mut info := live.info()
+    info.recheck_period_ms = 5
+	myprintln('START')
+	myprintln('DATE: ' + time.now().str())
 	pmessage()
-	time.sleep_ms(10)
 	pmessage()
-	for i := 0; i<3*100; i++ {
-		pmessage()
-		time.sleep_ms(10)
+    // NB: 1000 * 5 = maximum of ~5s runtime
+	for i:=0; i<1000; i++ {
+		s := pmessage()
+		append_to_file(os.resource_abs_path(s + '.txt'), s)
+		time.sleep_ms(delay)
+		if s == 'STOP' {
+			break
+		}
 	}
 	pmessage()
-	time.sleep_ms(10)
 	pmessage()
-	println('END')
+	myprintln('DATE: ' + time.now().str())
+	myprintln('END')
 }
 "
 )
 
+fn atomic_write_source( source string ){
+	// NB: here wrtiting is done in 2 steps, since os.write_file can take some time,
+	// during which the file will be modified, but it will still be not completely written.
+	// The os.mv after that, guarantees that the reloader will see a complete valid V program.
+	os.write_file(tmp_file, source)
+	os.mv(tmp_file, source_file )
+}
+
 //
 fn testsuite_begin() {
 	if os.user_os() !in ['linux', 'solaris'] && os.getenv('FORCE_LIVE_TEST').len == 0 {
@@ -39,16 +114,15 @@ fn testsuite_begin() {
 		eprintln('You can still do it by setting FORCE_LIVE_TEST=1 .')
 		exit(0)
 	}
-	os.write_file(source_file, live_program_source)
+	for f in [ tmp_file, source_file, output_file, res_original_file, res_changed_file, res_another_file, res_stop_file] {
+		os.rm(f)
+	}
+	atomic_write_source( live_program_source )
 }
 
 fn testsuite_end() {
-	os.rm(source_file)
 	eprintln('source: $source_file')
 	eprintln('output: $output_file')
-	$if !windows {
-		os.system('cat $output_file | sort | uniq -c | sort -n')
-	}
 	println('---------------------------------------------------------------------------')
 	output_lines := os.read_lines(output_file) or {
 		return
@@ -58,31 +132,51 @@ fn testsuite_end() {
 		histogram[line] = histogram[line] + 1
 	}
 	for k, v in histogram {
-		println('> found ${k} $v times.')
+		println('> found ${v:5d} times: ${k}')
 	}
 	println('---------------------------------------------------------------------------')
 	assert histogram['START'] > 0
-	assert histogram['END'] > 0
 	assert histogram['ORIGINAL'] > 0
 	assert histogram['CHANGED'] + histogram['ANOTHER'] > 0
+	//assert histogram['END'] > 0
 }
 
 fn change_source(new string) {
-	time.sleep_ms(250)
+	time.sleep_ms(100)
 	eprintln('> change ORIGINAL to: $new')
-	os.write_file(source_file, live_program_source.replace('ORIGINAL', new))
-	time.sleep_ms(1000)
-	eprintln('> done.')
+	atomic_write_source( live_program_source.replace('ORIGINAL', new) )
+	wait_for_file(new)
+}    
+
+fn wait_for_file(new string){    
+	time.sleep_ms(100)
+	expected_file := os.join_path(os.temp_dir(), new + '.txt')
+	for i:=0 ; i <= 400 ; i++ {
+		if i % 25 == 0 {
+			eprintln('   checking ${i:-10d} for $expected_file ...')
+		}
+		if os.exists( expected_file ) {
+			assert true
+			eprintln('> done.')
+			time.sleep_ms(100)
+			break
+		}
+		time.sleep_ms(5)
+	}
 }
 
 //
 fn test_live_program_can_be_compiled() {
-	cmd := '$vexe -live run $source_file > $output_file &'
-	eprintln('Compiling and running with: $cmd')
+	eprintln('Compiling...')
+	os.system('$vexe -live -o $genexe_file $source_file')
+	//
+	cmd := '$genexe_file > /dev/null &'
+	eprintln('Running with: $cmd')
 	res := os.system(cmd)
-	eprintln('... running in the background')
-	time.sleep_ms(1500)
 	assert res == 0
+	time.sleep_ms(1000)
+	eprintln('... running in the background')
+	wait_for_file('ORIGINAL')
 }
 
 fn test_live_program_can_be_changed_1() {
@@ -95,7 +189,7 @@ fn test_live_program_can_be_changed_2() {
 	assert true
 }
 
-fn test_live_program_has_ended() {
-	time.sleep_ms(3500)
+fn test_live_program_can_be_changed_3() {
+	change_source('STOP')
 	assert true
 }