From d27ab09cdfa702c8d548d4ccccf0361d1bb76380 Mon Sep 17 00:00:00 2001
From: larpon <768942+larpon@users.noreply.github.com>
Date: Tue, 10 Sep 2024 16:04:40 +0200
Subject: [PATCH] flag: add a relaxed parsing mode, that turn flag match errors
 into `no_match` entries instead (#22191)

---
 vlib/flag/flag_to.v              | 34 ++++++++++++++++++++++--
 vlib/flag/flag_to_misc_test.v    | 35 ++++++++++++++++++++++++-
 vlib/flag/flag_to_relaxed_test.v | 45 ++++++++++++++++++++++++++++++++
 3 files changed, 111 insertions(+), 3 deletions(-)
 create mode 100644 vlib/flag/flag_to_relaxed_test.v

diff --git a/vlib/flag/flag_to.v b/vlib/flag/flag_to.v
index 2b3a23f86..614e5f1a8 100644
--- a/vlib/flag/flag_to.v
+++ b/vlib/flag/flag_to.v
@@ -18,6 +18,11 @@ struct FlagContext {
 	pos       int    // position in arg array
 }
 
+pub enum ParseMode {
+	strict  // return errors for unknown or malformed flags per default
+	relaxed // relax flag match errors and add them to `no_match` list instead
+}
+
 pub enum Style {
 	short         // Posix short only, allows multiple shorts -def is `-d -e -f` and "sticky" arguments e.g.: `-ofoo` = `-o foo`
 	long          // GNU style long option *only*. E.g.: `--name` or `--name=value`
@@ -73,8 +78,9 @@ fn (sf StructField) shortest_match_name() ?string {
 @[params]
 pub struct ParseConfig {
 pub:
-	delimiter string = '-'         // delimiter used for flags
-	style     Style  = .short_long // expected flag style
+	delimiter string    = '-'         // delimiter used for flags
+	mode      ParseMode = .strict     // return errors for unknown or malformed flags per default
+	style     Style     = .short_long // expected flag style
 	stop      ?string // single, usually '--', string that stops parsing flags/options
 	skip      u16     // skip this amount in the input argument array, usually `1` for skipping executable or subcmd entry
 }
@@ -422,27 +428,51 @@ pub fn (mut fm FlagMapper) parse[T]() ! {
 			is_short_delimiter := used_delimiter.count(delimiter) == 1
 			is_invalid_delimiter := !is_long_delimiter && !is_short_delimiter
 			if is_invalid_delimiter {
+				if config.mode == .relaxed {
+					fm.no_match << pos
+					continue
+				}
 				return error('invalid delimiter `${used_delimiter}` for flag `${arg}`')
 			}
 			if is_long_delimiter {
 				if style == .v {
+					if config.mode == .relaxed {
+						fm.no_match << pos
+						continue
+					}
 					return error('long delimiter `${used_delimiter}` encountered in flag `${arg}` in ${style} (V) style parsing mode. Maybe you meant `.v_flag_parser`?')
 				}
 				if style == .short {
+					if config.mode == .relaxed {
+						fm.no_match << pos
+						continue
+					}
 					return error('long delimiter `${used_delimiter}` encountered in flag `${arg}` in ${style} (POSIX) style parsing mode')
 				}
 			}
 
 			if is_short_delimiter {
 				if style == .long {
+					if config.mode == .relaxed {
+						fm.no_match << pos
+						continue
+					}
 					return error('short delimiter `${used_delimiter}` encountered in flag `${arg}` in ${style} (GNU) style parsing mode')
 				}
 				if style == .short_long && flag_name.len > 1 && flag_name.contains('-') {
+					if config.mode == .relaxed {
+						fm.no_match << pos
+						continue
+					}
 					return error('long name `${flag_name}` used with short delimiter `${used_delimiter}` in flag `${arg}` in ${style} (POSIX/GNU) style parsing mode')
 				}
 			}
 
 			if flag_name == '' {
+				if config.mode == .relaxed {
+					fm.no_match << pos
+					continue
+				}
 				return error('invalid delimiter-only flag `${arg}`')
 			}
 
diff --git a/vlib/flag/flag_to_misc_test.v b/vlib/flag/flag_to_misc_test.v
index 5b1d521e1..3c56181ec 100644
--- a/vlib/flag/flag_to_misc_test.v
+++ b/vlib/flag/flag_to_misc_test.v
@@ -1,6 +1,6 @@
 import flag
 
-const all_style_enums = [flag.Style.short, .short_long, .long, .v]
+const all_style_enums = [flag.Style.short, .short_long, .long, .v, .v_flag_parser]
 const posix_gnu_style_enums = [flag.Style.short, .short_long, .long]
 const mixed_args = ['/path/to/exe', '-vv', 'vvv', '-version', '--mix', '--mix-all=all', '-ldflags',
 	'-m', '2', '-fgh', '["test", "test"]', '-m', '{map: 2, ml-q:"hello"}']
@@ -169,3 +169,36 @@ fn test_flag_error_messages() {
 		assert no_matches == ['--some-test=ouch']
 	}
 }
+
+fn test_flag_no_error_messages_when_relaxed() {
+	// Test that there's no errors in `mode: .relaxed`
+	_, no_matches1 := flag.to_struct[Config](posix_and_gnu_args_with_subcmd,
+		skip:  1
+		style: .short
+		mode:  .relaxed
+	)!
+	assert no_matches1 == ['subcmd', '--device=two', '--amount=8']
+
+	_, no_matches2 := flag.to_struct[LongConfig](gnu_args_error,
+		style: .long
+		mode:  .relaxed
+	)!
+	assert no_matches2 == ['oo']
+
+	if _, _ := flag.to_struct[LongConfig](['--version=1.2.3'],
+		style: .long
+		mode:  .relaxed
+	)
+	{
+		assert false, 'flags should not have reached this assert'
+	} else {
+		// Type errors should not be ignored, only non-matching flags/args
+		assert err.msg() == 'flag `--version=1.2.3` can not be assigned to bool field "show_version"'
+	}
+
+	_, no_matches3 := flag.to_struct[IgnoreConfig](ignore_args_error,
+		style: .long
+		mode:  .relaxed
+	)!
+	assert no_matches3 == ['--some-test=ouch']
+}
diff --git a/vlib/flag/flag_to_relaxed_test.v b/vlib/flag/flag_to_relaxed_test.v
new file mode 100644
index 000000000..029a0075f
--- /dev/null
+++ b/vlib/flag/flag_to_relaxed_test.v
@@ -0,0 +1,45 @@
+import flag
+
+const one_ok_gnu_arg_no_tail = ['-flip', '--g', '/path/to', '--mix', '-ver']
+const two_ok_gnu_arg_no_tail = ['-flip', '--g', '--sound=blop', '/path/to', '--mix', '-ver']
+
+const one_ok_gnu_arg_tail = ['-flip', '--g', '/path/to', '--mix', '-ver', 'tail']
+const two_ok_gnu_arg_tail = ['-flip', '--g', '--sound=blop', '/path/to', '--mix', '-ver', 'tail']
+
+struct Config {
+	mix   bool
+	sound string
+	beep  bool
+	path  string @[tail]
+}
+
+fn test_flag_relaxed_mode() {
+	// Test `mode: .relaxed`
+	config1, no_matches1 := flag.to_struct[Config](one_ok_gnu_arg_no_tail, mode: .relaxed)!
+	assert config1.mix == true
+	assert config1.sound == ''
+	assert config1.beep == false
+	assert config1.path == ''
+	assert no_matches1 == ['-flip', '--g', '/path/to', '-ver']
+
+	config2, no_matches2 := flag.to_struct[Config](two_ok_gnu_arg_no_tail, mode: .relaxed)!
+	assert config2.mix == true
+	assert config2.sound == 'blop'
+	assert config2.beep == false
+	assert config2.path == ''
+	assert no_matches2 == ['-flip', '--g', '/path/to', '-ver']
+
+	config3, no_matches3 := flag.to_struct[Config](one_ok_gnu_arg_tail, mode: .relaxed)!
+	assert config3.mix == true
+	assert config3.sound == ''
+	assert config3.beep == false
+	assert config3.path == 'tail'
+	assert no_matches3 == ['-flip', '--g', '/path/to', '-ver']
+
+	config4, no_matches4 := flag.to_struct[Config](two_ok_gnu_arg_tail, mode: .relaxed)!
+	assert config4.mix == true
+	assert config4.sound == 'blop'
+	assert config4.beep == false
+	assert config4.path == 'tail'
+	assert no_matches4 == ['-flip', '--g', '/path/to', '-ver']
+}
-- 
2.39.5