tools: turn v -watch into a v watch sub-command, so that it can have its own options

cmd/tools/vwatch.v

@@ -3,6 +3,7 @@ module main
 import os
 import time
 import term
+import flag
 
 const scan_timeout_s = 5 * 60
 
@@ -37,7 +38,7 @@ const max_scan_cycles = scan_timeout_s * scan_frequency_hz
 //   workers, thus it does not leak much.
 //
 //   b) A worker process, doing the actual monitoring/polling.
-//    NB: *workers are started with the -vwatchworker option*
+//    NB: *workers are started with the --vwatchworker option*
 //
 //    Worker processes will run for a limited number of iterations, then
 // they will do exit(255), and then the parent will start a new worker.
@@ -259,15 +260,38 @@ fn main() {
 	mut context := unsafe { &Context(voidptr(&ccontext)) }
 	context.pid = os.getpid()
 	context.vexe = os.getenv('VEXE')
-	context.is_worker = os.args.contains('-vwatchworker')
-	context.clear_terminal = os.getenv('VWATCH_CLEAR_TERMINAL') != ''
-	context.add_files = os.getenv('VWATCH_ADD_FILES').split(',')
-	context.ignore_exts = os.getenv('VWATCH_IGNORE_EXTENSIONS').split(',')
-	context.opts = os.args[1..].filter(it != '-vwatchworker')
+
+	mut fp := flag.new_flag_parser(os.args[1..])
+	fp.application('v watch')
+	if os.args[1] == 'watch' {
+		fp.skip_executable()
+	}
+	fp.version('0.0.2')
+	fp.description('Collect all .v files needed for a compilation, then re-run the compilation when any of the source changes.')
+	fp.arguments_description('[--clear] [--ignore .db] [--add /path/to/a/file.v] [run] program.v')
+	fp.allow_unknown_args()
+	fp.limit_free_args_to_at_least(1)
+	context.is_worker = fp.bool('vwatchworker', 0, false, 'Internal flag. Used to distinguish vwatch manager and worker processes.')
+	context.clear_terminal = fp.bool('clear', `c`, false, 'Clears the terminal before each re-run.')
+	context.add_files = fp.string('add', `a`, '', 'Add more files to be watched. Useful with `v watch -add=/tmp/feature.v run cmd/v /tmp/feature.v`, when you want to change *both* the compiler, and the feature.v file.').split(',')
+	context.ignore_exts = fp.string('ignore', `i`, '', 'Ignore files having these extensions. Useful with `v watch -ignore=.db run server.v`, if your server writes to an sqlite.db file in the same folder.').split(',')
+	show_help := fp.bool('help', `h`, false, 'Show this help screen.')
+	if show_help {
+		println(fp.usage())
+		exit(0)
+	}
+	remaining_options := fp.finalize() or {
+		eprintln('Error: $err')
+		exit(1)
+	}
+	context.opts = remaining_options
 	context.elog('>>> context.pid: $context.pid')
 	context.elog('>>> context.vexe: $context.vexe')
 	context.elog('>>> context.opts: $context.opts')
 	context.elog('>>> context.is_worker: $context.is_worker')
+	context.elog('>>> context.clear_terminal: $context.clear_terminal')
+	context.elog('>>> context.add_files: $context.add_files')
+	context.elog('>>> context.ignore_exts: $context.ignore_exts')
 	if context.is_worker {
 		context.worker_main()
 	} else {
@@ -277,8 +301,8 @@ fn main() {
 
 fn (mut context Context) manager_main() {
 	myexecutable := os.executable()
-	mut worker_opts := ['-vwatchworker']
-	worker_opts << context.opts
+	mut worker_opts := ['--vwatchworker']
+	worker_opts << os.args[2..]
 	for {
 		mut worker_process := os.new_process(myexecutable)
 		worker_process.set_args(worker_opts)

cmd/v/v.v

@@ -35,6 +35,7 @@ const (
 		'up',
 		'vet',
 		'wipe-cache',
+		'watch',
 	]
 	list_of_flags_that_allow_duplicates = ['cc', 'd', 'define', 'cf', 'cflags']
 )
@@ -69,9 +70,6 @@ fn main() {
 	}
 	args_and_flags := util.join_env_vflags_and_os_args()[1..]
 	prefs, command := pref.parse_args(external_tools, args_and_flags)
-	if prefs.is_watch {
-		util.launch_tool(prefs.is_verbose, 'vwatch', os.args[1..].filter(it != '-watch'))
-	}
 	if prefs.is_verbose {
 		// println('args= ')
 		// println(args) // QTODO

vlib/flag/flag.v

@@ -65,6 +65,7 @@ pub mut:
 	application_description string
 	min_free_args           int
 	args_description        string
+	allow_unknown_args      bool // whether passing undescribed arguments is allowed
 }
 
 [unsafe]
@@ -123,6 +124,14 @@ pub fn (mut fs FlagParser) skip_executable() {
 	fs.args.delete(0)
 }
 
+// allow_unknown_args - if your program has sub commands, that have
+// their own arguments, you can call .allow_unknown_args(), so that
+// the subcommand arguments (which generally are not known to your
+// parent program), will not cause the validation in .finalize() to fail.
+pub fn (mut fs FlagParser) allow_unknown_args() {
+	fs.allow_unknown_args = true
+}
+
 // private helper to register a flag
 fn (mut fs FlagParser) add_flag(name string, abbr byte, usage string, desc string) {
 	fs.flags << Flag{
@@ -495,6 +504,7 @@ pub fn (fs FlagParser) usage() string {
 // defined on the command line. If additional flags are found, i.e.
 // (things starting with '--' or '-'), it returns an error.
 pub fn (fs FlagParser) finalize() ?[]string {
+	if !fs.allow_unknown_args {
 		for a in fs.args {
 			if (a.len >= 2 && a[..2] == '--') || (a.len == 2 && a[0] == `-`) {
 				return IError(&UnkownFlagError{
@@ -502,6 +512,7 @@ pub fn (fs FlagParser) finalize() ?[]string {
 				})
 			}
 		}
+	}
 	if fs.args.len < fs.min_free_args && fs.min_free_args > 0 {
 		return IError(&MinimumArgsCountError{
 			msg: 'Expected at least $fs.min_free_args arguments, but given $fs.args.len'

vlib/v/pref/pref.v

@@ -84,7 +84,6 @@ pub mut:
 	output_mode OutputMode = .stdout
 	// verbosity           VerboseLevel
 	is_verbose bool
-	is_watch   bool // -watch mode, implemented by cmd/tools/watch.v
 	// nofmt            bool   // disable vfmt
 	is_test           bool   // `v test string_test.v`
 	is_script         bool   // single file mode (`v program.v`), main function can be skipped
@@ -447,7 +446,8 @@ pub fn parse_args(known_external_commands []string, args []string) (&Preferences
 				res.skip_warnings = true
 			}
 			'-watch' {
-				res.is_watch = true
+				eprintln('The -watch option is deprecated. Please use the watch command `v watch file.v` instead.')
+				exit(1)
 			}
 			'-print-v-files' {
 				res.print_v_files = true