v: add support for `v crun examples/hello_world.v`, use crun mode for .vsh files by default. (#14554)

cmd/v/help/default.txt

@@ -7,6 +7,7 @@ Examples:
    v hello.v                 Compile the file `hello.v` and output it as `hello` or `hello.exe`.
    v run hello.v             Same as above but also run the produced executable immediately after compilation.
    v -cg run hello.v         Same as above, but make debugging easier (in case your program crashes).
+   v crun hello.v            Same as above, but do not recompile, if the executable already exists, and is newer than the sources.
    v -o h.c hello.v          Translate `hello.v` to `h.c`. Do not compile further.
    v -o - hello.v            Translate `hello.v` and output the C source code to stdout. Do not compile further.
 
@@ -20,7 +21,10 @@ V supports the following commands:
    init              Setup the file structure for an already existing V project.
 
 * Ordinary development:
-   run               Compile and run a V program.
+   run               Compile and run a V program. Delete the executable after the run.
+   crun              Compile and run a V program without deleting the executable.
+                     If you run the same program a second time, without changing the source files,
+                     V will just run the executable, without recompilation. Suitable for scripting.
    test              Run all test files in the provided directory.
    fmt               Format the V code provided.
    vet               Report suspicious code constructs.

cmd/v/v.v

@@ -93,17 +93,21 @@ fn main() {
 		return
 	}
 	match command {
+		'run', 'crun', 'build', 'build-module' {
+			rebuild(prefs)
+			return
+		}
 		'help' {
 			invoke_help_and_exit(args)
 		}
+		'version' {
+			println(version.full_v_version(prefs.is_verbose))
+			return
+		}
 		'new', 'init' {
 			util.launch_tool(prefs.is_verbose, 'vcreate', os.args[1..])
 			return
 		}
-		'translate' {
-			eprintln('Translating C to V will be available in V 0.3')
-			exit(1)
-		}
 		'install', 'list', 'outdated', 'remove', 'search', 'show', 'update', 'upgrade' {
 			util.launch_tool(prefs.is_verbose, 'vpm', os.args[1..])
 			return
@@ -118,42 +122,24 @@ fn main() {
 			eprintln('V Error: Use `v install` to install modules from vpm.vlang.io')
 			exit(1)
 		}
-		'version' {
+		'translate' {
-			println(version.full_v_version(prefs.is_verbose))
+			eprintln('Translating C to V will be available in V 0.3')
-			return
+			exit(1)
 		}
-		else {}
+		else {
-	}
+			if command.ends_with('.v') || os.exists(command) {
-	if command in ['run', 'build', 'build-module'] || command.ends_with('.v') || os.exists(command) {
+				// println('command')
-		// println('command')
+				// println(prefs.path)
-		// println(prefs.path)
+				rebuild(prefs)
-		match prefs.backend {
+				return
-			.c {
-				$if no_bootstrapv ? {
-					// TODO: improve the bootstrapping with a split C backend here.
-					// C code generated by `VEXE=v cmd/tools/builders/c_builder -os cross -o c.c cmd/tools/builders/c_builder.v`
-					// is enough to bootstrap the C backend, and thus the rest, but currently bootstrapping relies on
-					// `v -os cross -o v.c cmd/v` having a functional C codegen inside instead.
-					util.launch_tool(prefs.is_verbose, 'builders/c_builder', os.args[1..])
-				}
-				builder.compile('build', prefs, cbuilder.compile_c)
-			}
-			.js_node, .js_freestanding, .js_browser {
-				util.launch_tool(prefs.is_verbose, 'builders/js_builder', os.args[1..])
-			}
-			.native {
-				util.launch_tool(prefs.is_verbose, 'builders/native_builder', os.args[1..])
-			}
-			.interpret {
-				util.launch_tool(prefs.is_verbose, 'builders/interpret_builder', os.args[1..])
 			}
 		}
-		return
 	}
 	if prefs.is_help {
 		invoke_help_and_exit(args)
 	}
-	eprintln('v $command: unknown command\nRun ${term.highlight_command('v help')} for usage.')
+	eprintln('v $command: unknown command')
+	eprintln('Run ${term.highlight_command('v help')} for usage.')
 	exit(1)
 }
 
@@ -163,7 +149,31 @@ fn invoke_help_and_exit(remaining []string) {
 		2 { help.print_and_exit(remaining[1]) }
 		else {}
 	}
-	println('${term.highlight_command('v help')}: provide only one help topic.')
+	eprintln('${term.highlight_command('v help')}: provide only one help topic.')
-	println('For usage information, use ${term.highlight_command('v help')}.')
+	eprintln('For usage information, use ${term.highlight_command('v help')}.')
 	exit(1)
 }
+
+fn rebuild(prefs &pref.Preferences) {
+	match prefs.backend {
+		.c {
+			$if no_bootstrapv ? {
+				// TODO: improve the bootstrapping with a split C backend here.
+				// C code generated by `VEXE=v cmd/tools/builders/c_builder -os cross -o c.c cmd/tools/builders/c_builder.v`
+				// is enough to bootstrap the C backend, and thus the rest, but currently bootstrapping relies on
+				// `v -os cross -o v.c cmd/v` having a functional C codegen inside instead.
+				util.launch_tool(prefs.is_verbose, 'builders/c_builder', os.args[1..])
+			}
+			builder.compile('build', prefs, cbuilder.compile_c)
+		}
+		.js_node, .js_freestanding, .js_browser {
+			util.launch_tool(prefs.is_verbose, 'builders/js_builder', os.args[1..])
+		}
+		.native {
+			util.launch_tool(prefs.is_verbose, 'builders/native_builder', os.args[1..])
+		}
+		.interpret {
+			util.launch_tool(prefs.is_verbose, 'builders/interpret_builder', os.args[1..])
+		}
+	}
+}

vlib/v/builder/builder.v

@@ -17,7 +17,7 @@ import v.dotgraph
 
 pub struct Builder {
 pub:
-	compiled_dir string // contains os.real_path() of the dir of the final file beeing compiled, or the dir itself when doing `v .`
+	compiled_dir string // contains os.real_path() of the dir of the final file being compiled, or the dir itself when doing `v .`
 	module_path  string
 pub mut:
 	checker             &checker.Checker
@@ -40,6 +40,7 @@ pub mut:
 	mod_invalidates_paths map[string][]string // changes in mod `os`, invalidate only .v files, that do `import os`
 	mod_invalidates_mods  map[string][]string // changes in mod `os`, force invalidation of mods, that do `import os`
 	path_invalidates_mods map[string][]string // changes in a .v file from `os`, invalidates `os`
+	crun_cache_keys       []string // target executable + top level source files; filled in by Builder.should_rebuild
 }
 
 pub fn new_builder(pref &pref.Preferences) Builder {

vlib/v/builder/compile.v

@@ -3,9 +3,7 @@
 // that can be found in the LICENSE file.
 module builder
 
-import time
 import os
-import rand
 import v.pref
 import v.util
 import v.checker
@@ -13,6 +11,19 @@ import v.checker
 pub type FnBackend = fn (mut b Builder)
 
 pub fn compile(command string, pref &pref.Preferences, backend_cb FnBackend) {
+	check_if_output_folder_is_writable(pref)
+	// Construct the V object from command line arguments
+	mut b := new_builder(pref)
+	if b.should_rebuild() {
+		b.rebuild(backend_cb)
+	}
+	b.exit_on_invalid_syntax()
+	// running does not require the parsers anymore
+	unsafe { b.myfree() }
+	b.run_compiled_executable_and_exit()
+}
+
+fn check_if_output_folder_is_writable(pref &pref.Preferences) {
 	odir := os.dir(pref.out_name)
 	// When pref.out_name is just the name of an executable, i.e. `./v -o executable main.v`
 	// without a folder component, just use the current folder instead:
@@ -24,56 +35,6 @@ pub fn compile(command string, pref &pref.Preferences, backend_cb FnBackend) {
 		// An early error here, is better than an unclear C error later:
 		verror(err.msg())
 	}
-	// Construct the V object from command line arguments
-	mut b := new_builder(pref)
-	if pref.is_verbose {
-		println('builder.compile() pref:')
-		// println(pref)
-	}
-	mut sw := time.new_stopwatch()
-	backend_cb(mut b)
-	mut timers := util.get_timers()
-	timers.show_remaining()
-	if pref.is_stats {
-		compilation_time_micros := 1 + sw.elapsed().microseconds()
-		scompilation_time_ms := util.bold('${f64(compilation_time_micros) / 1000.0:6.3f}')
-		mut all_v_source_lines, mut all_v_source_bytes := 0, 0
-		for pf in b.parsed_files {
-			all_v_source_lines += pf.nr_lines
-			all_v_source_bytes += pf.nr_bytes
-		}
-		mut sall_v_source_lines := all_v_source_lines.str()
-		mut sall_v_source_bytes := all_v_source_bytes.str()
-		sall_v_source_lines = util.bold('${sall_v_source_lines:10s}')
-		sall_v_source_bytes = util.bold('${sall_v_source_bytes:10s}')
-		println('        V  source  code size: $sall_v_source_lines lines, $sall_v_source_bytes bytes')
-		//
-		mut slines := b.stats_lines.str()
-		mut sbytes := b.stats_bytes.str()
-		slines = util.bold('${slines:10s}')
-		sbytes = util.bold('${sbytes:10s}')
-		println('generated  target  code size: $slines lines, $sbytes bytes')
-		//
-		vlines_per_second := int(1_000_000.0 * f64(all_v_source_lines) / f64(compilation_time_micros))
-		svlines_per_second := util.bold(vlines_per_second.str())
-		println('compilation took: $scompilation_time_ms ms, compilation speed: $svlines_per_second vlines/s')
-	}
-	b.exit_on_invalid_syntax()
-	// running does not require the parsers anymore
-	unsafe { b.myfree() }
-	if pref.is_test || pref.is_run {
-		b.run_compiled_executable_and_exit()
-	}
-}
-
-pub fn (mut b Builder) get_vtmp_filename(base_file_name string, postfix string) string {
-	vtmp := util.get_vtmp_folder()
-	mut uniq := ''
-	if !b.pref.reuse_tmpc {
-		uniq = '.$rand.u64()'
-	}
-	fname := os.file_name(os.real_path(base_file_name)) + '$uniq$postfix'
-	return os.real_path(os.join_path(vtmp, fname))
 }
 
 // Temporary, will be done by -autofree
@@ -118,47 +79,45 @@ fn (mut b Builder) run_compiled_executable_and_exit() {
 	if b.pref.os == .ios {
 		panic('Running iOS apps is not supported yet.')
 	}
+	if !(b.pref.is_test || b.pref.is_run || b.pref.is_crun) {
+		exit(0)
+	}
+	compiled_file := os.real_path(b.pref.out_name)
+	run_file := if b.pref.backend.is_js() {
+		node_basename := $if windows { 'node.exe' } $else { 'node' }
+		os.find_abs_path_of_executable(node_basename) or {
+			panic('Could not find `node` in system path. Do you have Node.js installed?')
+		}
+	} else {
+		compiled_file
+	}
+	mut run_args := []string{cap: b.pref.run_args.len + 1}
+	if b.pref.backend.is_js() {
+		run_args << compiled_file
+	}
+	run_args << b.pref.run_args
+	mut run_process := os.new_process(run_file)
+	run_process.set_args(run_args)
 	if b.pref.is_verbose {
+		println('running $run_process.filename with arguments $run_process.args')
 	}
-	if b.pref.is_test || b.pref.is_run {
+	// Ignore sigint and sigquit while running the compiled file,
-		compiled_file := os.real_path(b.pref.out_name)
+	// so ^C doesn't prevent v from deleting the compiled file.
-		run_file := if b.pref.backend.is_js() {
+	// See also https://git.musl-libc.org/cgit/musl/tree/src/process/system.c
-			node_basename := $if windows { 'node.exe' } $else { 'node' }
+	prev_int_handler := os.signal_opt(.int, eshcb) or { serror('set .int', err) }
-			os.find_abs_path_of_executable(node_basename) or {
+	mut prev_quit_handler := os.SignalHandler(eshcb)
-				panic('Could not find `node` in system path. Do you have Node.js installed?')
+	$if !windows { // There's no sigquit on windows
-			}
+		prev_quit_handler = os.signal_opt(.quit, eshcb) or { serror('set .quit', err) }
-		} else {
-			compiled_file
-		}
-		mut run_args := []string{cap: b.pref.run_args.len + 1}
-		if b.pref.backend.is_js() {
-			run_args << compiled_file
-		}
-		run_args << b.pref.run_args
-		mut run_process := os.new_process(run_file)
-		run_process.set_args(run_args)
-		if b.pref.is_verbose {
-			println('running $run_process.filename with arguments $run_process.args')
-		}
-		// Ignore sigint and sigquit while running the compiled file,
-		// so ^C doesn't prevent v from deleting the compiled file.
-		// See also https://git.musl-libc.org/cgit/musl/tree/src/process/system.c
-		prev_int_handler := os.signal_opt(.int, eshcb) or { serror('set .int', err) }
-		mut prev_quit_handler := os.SignalHandler(eshcb)
-		$if !windows { // There's no sigquit on windows
-			prev_quit_handler = os.signal_opt(.quit, eshcb) or { serror('set .quit', err) }
-		}
-		run_process.wait()
-		os.signal_opt(.int, prev_int_handler) or { serror('restore .int', err) }
-		$if !windows {
-			os.signal_opt(.quit, prev_quit_handler) or { serror('restore .quit', err) }
-		}
-		ret := run_process.code
-		run_process.close()
-		b.cleanup_run_executable_after_exit(compiled_file)
-		exit(ret)
 	}
-	exit(0)
+	run_process.wait()
+	os.signal_opt(.int, prev_int_handler) or { serror('restore .int', err) }
+	$if !windows {
+		os.signal_opt(.quit, prev_quit_handler) or { serror('restore .quit', err) }
+	}
+	ret := run_process.code
+	run_process.close()
+	b.cleanup_run_executable_after_exit(compiled_file)
+	exit(ret)
 }
 
 fn eshcb(_ os.Signal) {
@@ -171,6 +130,9 @@ fn serror(reason string, e IError) {
 }
 
 fn (mut v Builder) cleanup_run_executable_after_exit(exefile string) {
+	if v.pref.is_crun {
+		return
+	}
 	if v.pref.reuse_tmpc {
 		v.pref.vrun_elog('keeping executable: $exefile , because -keepc was passed')
 		return

vlib/v/builder/rebuilding.v

@@ -2,6 +2,8 @@ module builder
 
 import os
 import hash
+import time
+import rand
 import strings
 import v.util
 import v.pref
@@ -11,11 +13,27 @@ pub fn (mut b Builder) rebuild_modules() {
 	if !b.pref.use_cache || b.pref.build_mode == .build_module {
 		return
 	}
+	all_files := b.parsed_files.map(it.path)
+	$if trace_invalidations ? {
+		eprintln('> rebuild_modules all_files: $all_files')
+	}
+	invalidations := b.find_invalidated_modules_by_files(all_files)
+	$if trace_invalidations ? {
+		eprintln('> rebuild_modules invalidations: $invalidations')
+	}
+	if invalidations.len > 0 {
+		vexe := pref.vexe_path()
+		for imp in invalidations {
+			b.v_build_module(vexe, imp)
+		}
+	}
+}
+
+pub fn (mut b Builder) find_invalidated_modules_by_files(all_files []string) []string {
 	util.timing_start('${@METHOD} source_hashing')
 	mut new_hashes := map[string]string{}
 	mut old_hashes := map[string]string{}
 	mut sb_new_hashes := strings.new_builder(1024)
-	all_files := b.parsed_files.map(it.path)
 	//
 	mut cm := vcache.new_cache_manager(all_files)
 	sold_hashes := cm.load('.hashes', 'all_files') or { ' ' }
@@ -31,8 +49,7 @@ pub fn (mut b Builder) rebuild_modules() {
 		old_hashes[cpath] = chash
 	}
 	// eprintln('old_hashes: $old_hashes')
-	for p in b.parsed_files {
+	for cpath in all_files {
-		cpath := p.path
 		ccontent := util.read_file(cpath) or { '' }
 		chash := hash.sum64_string(ccontent, 7).hex_full()
 		new_hashes[cpath] = chash
@@ -48,6 +65,7 @@ pub fn (mut b Builder) rebuild_modules() {
 	cm.save('.hashes', 'all_files', snew_hashes) or {}
 	util.timing_measure('${@METHOD} source_hashing')
 
+	mut invalidations := []string{}
 	if new_hashes != old_hashes {
 		util.timing_start('${@METHOD} rebuilding')
 		// eprintln('> b.mod_invalidates_paths: $b.mod_invalidates_paths')
@@ -148,13 +166,13 @@ pub fn (mut b Builder) rebuild_modules() {
 		}
 		if invalidated_mod_paths.len > 0 {
 			impaths := invalidated_mod_paths.keys()
-			vexe := pref.vexe_path()
 			for imp in impaths {
-				b.v_build_module(vexe, imp)
+				invalidations << imp
 			}
 		}
 		util.timing_measure('${@METHOD} rebuilding')
 	}
+	return invalidations
 }
 
 fn (mut b Builder) v_build_module(vexe string, imp_path string) {
@@ -237,3 +255,114 @@ fn (mut b Builder) handle_usecache(vexe string) {
 	}
 	b.ccoptions.post_args << libs
 }
+
+pub fn (mut b Builder) should_rebuild() bool {
+	mut exe_name := b.pref.out_name
+	$if windows {
+		exe_name = exe_name + '.exe'
+	}
+	if !os.is_file(exe_name) {
+		return true
+	}
+	if !b.pref.is_crun {
+		return true
+	}
+	mut v_program_files := []string{}
+	is_file := os.is_file(b.pref.path)
+	is_dir := os.is_dir(b.pref.path)
+	if is_file {
+		v_program_files << b.pref.path
+	} else if is_dir {
+		v_program_files << b.v_files_from_dir(b.pref.path)
+	}
+	v_program_files.sort() // ensure stable keys for the dependencies cache
+	b.crun_cache_keys = v_program_files
+	b.crun_cache_keys << exe_name
+	// just check the timestamps for now:
+	exe_stamp := os.file_last_mod_unix(exe_name)
+	source_stamp := most_recent_timestamp(v_program_files)
+	if exe_stamp <= source_stamp {
+		return true
+	}
+	////////////////////////////////////////////////////////////////////////////
+	// The timestamps for the top level files were found ok,
+	// however we want to *also* make sure that a full rebuild will be done
+	// if any of the dependencies (if we know them) are changed.
+	mut cm := vcache.new_cache_manager(b.crun_cache_keys)
+	// always rebuild, when the compilation options changed between 2 sequential cruns:
+	sbuild_options := cm.load('.build_options', '.crun') or { return true }
+	if sbuild_options != b.pref.build_options.join('\n') {
+		return true
+	}
+	sdependencies := cm.load('.dependencies', '.crun') or {
+		// empty/wiped out cache, we do not know what the dependencies are, so just
+		// rebuild, which will fill in the dependencies cache for the next crun
+		return true
+	}
+	dependencies := sdependencies.split('\n')
+	// we have already compiled these source files, and have their dependencies
+	dependencies_stamp := most_recent_timestamp(dependencies)
+	if dependencies_stamp < exe_stamp {
+		return false
+	}
+	return true
+}
+
+fn most_recent_timestamp(files []string) i64 {
+	mut res := i64(0)
+	for f in files {
+		f_stamp := os.file_last_mod_unix(f)
+		if res <= f_stamp {
+			res = f_stamp
+		}
+	}
+	return res
+}
+
+pub fn (mut b Builder) rebuild(backend_cb FnBackend) {
+	mut sw := time.new_stopwatch()
+	backend_cb(mut b)
+	if b.pref.is_crun {
+		// save the dependencies after the first compilation, they will be used for subsequent ones:
+		mut cm := vcache.new_cache_manager(b.crun_cache_keys)
+		dependency_files := b.parsed_files.map(it.path)
+		cm.save('.dependencies', '.crun', dependency_files.join('\n')) or {}
+		cm.save('.build_options', '.crun', b.pref.build_options.join('\n')) or {}
+	}
+	mut timers := util.get_timers()
+	timers.show_remaining()
+	if b.pref.is_stats {
+		compilation_time_micros := 1 + sw.elapsed().microseconds()
+		scompilation_time_ms := util.bold('${f64(compilation_time_micros) / 1000.0:6.3f}')
+		mut all_v_source_lines, mut all_v_source_bytes := 0, 0
+		for pf in b.parsed_files {
+			all_v_source_lines += pf.nr_lines
+			all_v_source_bytes += pf.nr_bytes
+		}
+		mut sall_v_source_lines := all_v_source_lines.str()
+		mut sall_v_source_bytes := all_v_source_bytes.str()
+		sall_v_source_lines = util.bold('${sall_v_source_lines:10s}')
+		sall_v_source_bytes = util.bold('${sall_v_source_bytes:10s}')
+		println('        V  source  code size: $sall_v_source_lines lines, $sall_v_source_bytes bytes')
+		//
+		mut slines := b.stats_lines.str()
+		mut sbytes := b.stats_bytes.str()
+		slines = util.bold('${slines:10s}')
+		sbytes = util.bold('${sbytes:10s}')
+		println('generated  target  code size: $slines lines, $sbytes bytes')
+		//
+		vlines_per_second := int(1_000_000.0 * f64(all_v_source_lines) / f64(compilation_time_micros))
+		svlines_per_second := util.bold(vlines_per_second.str())
+		println('compilation took: $scompilation_time_ms ms, compilation speed: $svlines_per_second vlines/s')
+	}
+}
+
+pub fn (mut b Builder) get_vtmp_filename(base_file_name string, postfix string) string {
+	vtmp := util.get_vtmp_folder()
+	mut uniq := ''
+	if !b.pref.reuse_tmpc {
+		uniq = '.$rand.u64()'
+	}
+	fname := os.file_name(os.real_path(base_file_name)) + '$uniq$postfix'
+	return os.real_path(os.join_path(vtmp, fname))
+}

vlib/v/pref/pref.v

@@ -111,7 +111,8 @@ pub mut:
 	is_prof           bool // benchmark every function
 	is_prod           bool // use "-O2"
 	is_repl           bool
-	is_run            bool
+	is_run            bool // compile and run a v program, passing arguments to it, and deleting the executable afterwards
+	is_crun           bool // similar to run, but does not recompile the executable, if there were no changes to the sources
 	is_debug          bool // turned on by -g or -cg, it tells v to pass -g to the C backend compiler.
 	is_vlines         bool // turned on by -g (it slows down .tmp.c generation slightly).
 	is_stats          bool // `v -stats file_test.v` will produce more detailed statistics for the tests that were run
@@ -706,7 +707,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 					if command == '' {
 						command = arg
 						command_pos = i
-						if command == 'run' {
+						if command in ['run', 'crun'] {
 							break
 						}
 					} else if is_source_file(command) && is_source_file(arg)
@@ -734,6 +735,12 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 	if res.is_debug {
 		res.parse_define('debug')
 	}
+	if command == 'crun' {
+		res.is_crun = true
+	}
+	if command == 'run' {
+		res.is_run = true
+	}
 	if command == 'run' && res.is_prod && os.is_atty(1) > 0 {
 		eprintln_cond(show_output, "Note: building an optimized binary takes much longer. It shouldn't be used with `v run`.")
 		eprintln_cond(show_output, 'Use `v run` without optimization, or build an optimized binary with -prod first, then run it separately.')
@@ -744,8 +751,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 		eprintln('Cannot save output binary in a .v file.')
 		exit(1)
 	}
-	if command == 'run' {
+	if res.is_run || res.is_crun {
-		res.is_run = true
 		if command_pos + 2 > args.len {
 			eprintln('v run: no v files listed')
 			exit(1)
@@ -798,7 +804,7 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 		// `v build.vsh gcc` is the same as `v run build.vsh gcc`,
 		// i.e. compiling, then running the script, passing the args
 		// after it to the script:
-		res.is_run = true
+		res.is_crun = true
 		res.path = command
 		res.run_args = args[command_pos + 1..]
 	} else if command == 'interpret' {

vlib/v/tests/crun_mode/crun_test.v

@@ -0,0 +1,51 @@
+import os
+import time
+
+const crun_folder = os.join_path(os.temp_dir(), 'crun_folder')
+
+const vprogram_file = os.join_path(crun_folder, 'vprogram.vv')
+
+const vexe = os.getenv('VEXE')
+
+fn testsuite_begin() {
+	os.setenv('VCACHE', crun_folder, true)
+	os.rmdir_all(crun_folder) or {}
+	os.mkdir_all(crun_folder) or {}
+	assert os.is_dir(crun_folder)
+}
+
+fn testsuite_end() {
+	os.chdir(os.wd_at_startup) or {}
+	os.rmdir_all(crun_folder) or {}
+	assert !os.is_dir(crun_folder)
+}
+
+fn test_saving_simple_v_program() ? {
+	os.write_file(vprogram_file, 'print("hello")')?
+	assert true
+}
+
+fn test_crun_simple_v_program_several_times() ? {
+	mut sw := time.new_stopwatch()
+	mut times := []i64{}
+	for i in 0 .. 10 {
+		vcrun()
+		times << sw.elapsed().microseconds()
+		time.sleep(50 * time.millisecond)
+		sw.restart()
+	}
+	dump(times)
+	assert times.first() > times.last() * 5 // cruns compile just once, if the source file is not changed
+	$if !windows {
+		os.system('ls -la $crun_folder')
+		os.system('find $crun_folder')
+	}
+}
+
+fn vcrun() {
+	cmd := '${os.quoted_path(vexe)} crun ${os.quoted_path(vprogram_file)}'
+	eprintln('now: $time.now().format_ss_milli() | cmd: $cmd')
+	res := os.execute(cmd)
+	assert res.exit_code == 0
+	assert res.output == 'hello'
+}