refactor(preg): split the PREG_UNMATCHED_AS_NULL preg_* by flag

preg_match2() and preg_match_all_offset_capture() each become a pair over
a shared private impl, and their flags arguments are gone: no caller passed
anything but 0 or PREG_UNMATCHED_AS_NULL. Preg::match5()/is_match5() lose
their own flags argument for the same reason -- both call sites passed 0,
and the value had nowhere left to go -- so they are renumbered to
match4()/is_match4(). PREG_UNMATCHED_AS_NULL itself is now unreferenced.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

6 files changed, 56 insertions, 39 deletions

diff --git a/crates/shirabe-class-map-generator/src/php_file_cleaner.rs b/crates/shirabe-class-map-generator/src/php_file_cleaner.rs
index eb2b84e4..c5952389 100644
--- a/crates/shirabe-class-map-generator/src/php_file_cleaner.rs
+++ b/crates/shirabe-class-map-generator/src/php_file_cleaner.rs
@@ -145,11 +145,10 @@ impl PhpFileCleaner {
                         if end <= self.len && self.contents[self.index..end] == entry.name {
                             let offset = if self.index > 0 { self.index - 1 } else { 0 };
                             let mut r#match: IndexMap<CaptureKey, String> = IndexMap::new();
-                            if Preg::is_match5(
+                            if Preg::is_match4(
                                 &entry.pattern,
                                 &self.contents,
                                 Some(&mut r#match),
-                                0,
                                 offset,
                             ) {
                                 return clean
@@ -294,6 +293,6 @@ impl PhpFileCleaner {
     }
 
     fn r#match(&self, regex: &str, r#match: Option<&mut IndexMap<CaptureKey, String>>) -> bool {
-        Preg::is_match5(regex, &self.contents, r#match, 0, self.index)
+        Preg::is_match4(regex, &self.contents, r#match, self.index)
     }
 }
diff --git a/crates/shirabe-pcre/src/preg.rs b/crates/shirabe-pcre/src/preg.rs
index fb71c63b..0448f81a 100644
--- a/crates/shirabe-pcre/src/preg.rs
+++ b/crates/shirabe-pcre/src/preg.rs
@@ -14,8 +14,8 @@
 use indexmap::IndexMap;
 pub use shirabe_php_shim::CaptureKey;
 use shirabe_php_shim::{
-    PREG_UNMATCHED_AS_NULL, PregPattern, preg_grep, preg_match_all_offset_capture, preg_match_all2,
-    preg_match2, preg_replace_callback, preg_replace2,
+    PregPattern, preg_grep, preg_match_all_offset_capture_unmatched_as_null, preg_match_all2,
+    preg_match2, preg_match2_unmatched_as_null, preg_replace_callback, preg_replace2,
 };
 
 #[derive(Debug)]
@@ -27,24 +27,17 @@ impl Preg {
         subject: &str,
         matches: Option<&mut IndexMap<CaptureKey, String>>,
     ) -> bool {
-        Self::match5(pattern, subject, matches, 0, 0)
+        Self::match4(pattern, subject, matches, 0)
     }
 
-    pub fn match5(
+    pub fn match4(
         pattern: impl PregPattern,
         subject: &str,
         matches: Option<&mut IndexMap<CaptureKey, String>>,
-        flags: i64,
         offset: usize,
     ) -> bool {
         let mut internal: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
-        let result = preg_match2(
-            pattern,
-            subject,
-            &mut internal,
-            flags | PREG_UNMATCHED_AS_NULL,
-            offset,
-        );
+        let result = preg_match2_unmatched_as_null(pattern, subject, &mut internal, offset);
 
         if let Some(out) = matches {
             *out = drop_null_matches(internal);
@@ -73,7 +66,7 @@ impl Preg {
     ) -> usize {
         let mut internal: IndexMap<CaptureKey, Vec<(Option<String>, i64)>> = IndexMap::new();
         let result =
-            preg_match_all_offset_capture(pattern, subject, &mut internal, PREG_UNMATCHED_AS_NULL);
+            preg_match_all_offset_capture_unmatched_as_null(pattern, subject, &mut internal);
 
         if let Some(out) = matches {
             *out = internal;
@@ -125,7 +118,7 @@ impl Preg {
     }
 
     pub fn is_match(pattern: impl PregPattern, subject: &str) -> bool {
-        Self::match5(pattern, subject, None, 0, 0)
+        Self::match4(pattern, subject, None, 0)
     }
 
     pub fn is_match3(
@@ -133,17 +126,16 @@ impl Preg {
         subject: &str,
         matches: Option<&mut IndexMap<CaptureKey, String>>,
     ) -> bool {
-        Self::match5(pattern, subject, matches, 0, 0)
+        Self::match4(pattern, subject, matches, 0)
     }
 
-    pub fn is_match5(
+    pub fn is_match4(
         pattern: impl PregPattern,
         subject: &str,
         matches: Option<&mut IndexMap<CaptureKey, String>>,
-        flags: i64,
         offset: usize,
     ) -> bool {
-        Self::match5(pattern, subject, matches, flags, offset)
+        Self::match4(pattern, subject, matches, offset)
     }
 
     pub fn is_match_named(
@@ -152,7 +144,7 @@ impl Preg {
         matches: &mut IndexMap<String, String>,
     ) -> bool {
         let mut internal: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
-        let result = preg_match2(pattern, subject, &mut internal, PREG_UNMATCHED_AS_NULL, 0);
+        let result = preg_match2_unmatched_as_null(pattern, subject, &mut internal, 0);
 
         matches.clear();
         for (key, value) in internal {
@@ -171,7 +163,7 @@ impl Preg {
         // Classic preg_match semantics (no PREG_UNMATCHED_AS_NULL): trailing
         // unmatched groups are truncated, interior unmatched groups become "".
         let mut internal: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
-        let result = preg_match2(pattern, subject, &mut internal, 0, 0);
+        let result = preg_match2(pattern, subject, &mut internal, 0);
 
         if !result {
             return None;
diff --git a/crates/shirabe-php-shim/src/preg.rs b/crates/shirabe-php-shim/src/preg.rs
index 1156129a..0d6a3231 100644
--- a/crates/shirabe-php-shim/src/preg.rs
+++ b/crates/shirabe-php-shim/src/preg.rs
@@ -1,8 +1,6 @@
 use indexmap::IndexMap;
 use std::sync::{Arc, LazyLock, Mutex};
 
-pub const PREG_UNMATCHED_AS_NULL: i64 = 512;
-
 #[derive(Debug, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
 pub enum CaptureKey {
     ByIndex(usize),
@@ -51,18 +49,35 @@ pub fn preg_match(
     }
 }
 
-// Returns whether the pattern matched. Unmatched groups are reported as None
-// (PREG_UNMATCHED_AS_NULL).
+// Returns whether the pattern matched, reporting the groups as single_match_map() does.
 pub fn preg_match2(
     pattern: impl PregPattern,
     subject: &str,
     matches: &mut indexmap::IndexMap<CaptureKey, Option<String>>,
-    flags: i64,
     offset: usize,
 ) -> bool {
+    preg_match2_impl(pattern, subject, matches, offset, false)
+}
+
+// PREG_UNMATCHED_AS_NULL counterpart of preg_match2().
+pub fn preg_match2_unmatched_as_null(
+    pattern: impl PregPattern,
+    subject: &str,
+    matches: &mut indexmap::IndexMap<CaptureKey, Option<String>>,
+    offset: usize,
+) -> bool {
+    preg_match2_impl(pattern, subject, matches, offset, true)
+}
+
+fn preg_match2_impl(
+    pattern: impl PregPattern,
+    subject: &str,
+    matches: &mut indexmap::IndexMap<CaptureKey, Option<String>>,
+    offset: usize,
+    unmatched_as_null: bool,
+) -> bool {
     let __resolved = pattern.resolve();
     let (re, anchored) = __resolved.parts();
-    let unmatched_as_null = flags & PREG_UNMATCHED_AS_NULL != 0;
     // An anchored (`A`) pattern must match starting exactly at `offset`; the `regex` crate cannot
     // anchor a `captures_at` search, so search the sub-slice beginning at `offset` and require the
     // match to start at its head.
@@ -155,15 +170,33 @@ pub fn preg_match_all_set_order(
     count
 }
 
+// A non-participating group is reported at offset -1, holding "".
 pub fn preg_match_all_offset_capture(
     pattern: impl PregPattern,
     subject: &str,
     matches: &mut indexmap::IndexMap<CaptureKey, Vec<(Option<String>, i64)>>,
-    flags: i64,
+) -> usize {
+    preg_match_all_offset_capture_impl(pattern, subject, matches, false)
+}
+
+// PREG_UNMATCHED_AS_NULL counterpart of preg_match_all_offset_capture(): a
+// non-participating group holds null instead of "".
+pub fn preg_match_all_offset_capture_unmatched_as_null(
+    pattern: impl PregPattern,
+    subject: &str,
+    matches: &mut indexmap::IndexMap<CaptureKey, Vec<(Option<String>, i64)>>,
+) -> usize {
+    preg_match_all_offset_capture_impl(pattern, subject, matches, true)
+}
+
+fn preg_match_all_offset_capture_impl(
+    pattern: impl PregPattern,
+    subject: &str,
+    matches: &mut indexmap::IndexMap<CaptureKey, Vec<(Option<String>, i64)>>,
+    unmatched_as_null: bool,
 ) -> usize {
     let __resolved = pattern.resolve();
     let (re, _anchored) = __resolved.parts();
-    let unmatched_as_null = flags & PREG_UNMATCHED_AS_NULL != 0;
     let group_count = re.captures_len();
     let names: Vec<Option<&str>> = re.capture_names().collect();
 
@@ -172,8 +205,6 @@ pub fn preg_match_all_offset_capture(
     for caps in re.captures_iter(subject) {
         count += 1;
         for (g, column) in groups.iter_mut().enumerate() {
-            // A non-participating group is reported at offset -1, holding "" or,
-            // with PREG_UNMATCHED_AS_NULL, null.
             let entry = match caps.get(g) {
                 Some(m) => (Some(m.as_str().to_string()), m.start() as i64),
                 None if unmatched_as_null => (None, -1),
diff --git a/crates/shirabe-symfony-console/src/formatter/output_formatter.rs b/crates/shirabe-symfony-console/src/formatter/output_formatter.rs
index 6ce96875..1a3de217 100644
--- a/crates/shirabe-symfony-console/src/formatter/output_formatter.rs
+++ b/crates/shirabe-symfony-console/src/formatter/output_formatter.rs
@@ -296,7 +296,6 @@ impl WrappableOutputFormatterInterface for OutputFormatter {
             format!("#<(({open_tag_regex}) | /({close_tag_regex})?)>#ix"),
             message,
             &mut matches,
-            0,
         );
         let full_matches = matches
             .get(&CaptureKey::ByIndex(0))
diff --git a/crates/shirabe-symfony-console/src/input/string_input.rs b/crates/shirabe-symfony-console/src/input/string_input.rs
index 1ec6e853..d6794957 100644
--- a/crates/shirabe-symfony-console/src/input/string_input.rs
+++ b/crates/shirabe-symfony-console/src/input/string_input.rs
@@ -58,7 +58,7 @@ impl StringInput {
             }
 
             let mut m: IndexMap<CaptureKey, Option<String>> = IndexMap::new();
-            if preg_match2(php_regex!(r"/\s+/A"), input, &mut m, 0, cursor as usize) {
+            if preg_match2(php_regex!(r"/\s+/A"), input, &mut m, cursor as usize) {
                 if token.is_some() {
                     tokens.push(token.take().unwrap());
                 }
@@ -68,7 +68,6 @@ impl StringInput {
                 format!(r#"/([^="'\s]+?)(=?)({}+)/A"#, Self::REGEX_QUOTED_STRING),
                 input,
                 &mut m,
-                0,
                 cursor as usize,
             ) {
                 let inner = shirabe_php_shim::substr(
@@ -91,7 +90,6 @@ impl StringInput {
                 format!(r"/{}/A", Self::REGEX_QUOTED_STRING),
                 input,
                 &mut m,
-                0,
                 cursor as usize,
             ) {
                 token = Some(format!(
@@ -109,7 +107,6 @@ impl StringInput {
                 format!(r"/{}/A", Self::REGEX_UNQUOTED_STRING),
                 input,
                 &mut m,
-                0,
                 cursor as usize,
             ) {
                 token = Some(format!(
diff --git a/crates/shirabe/src/console/application.rs b/crates/shirabe/src/console/application.rs
index b55b9e68..e818823e 100644
--- a/crates/shirabe/src/console/application.rs
+++ b/crates/shirabe/src/console/application.rs
@@ -1796,7 +1796,6 @@ impl Application {
             php_regex!(r"/.{1,10000}/u"),
             &utf8_string,
             &mut m,
-            0,
             offset as usize,
         ) {
             let m0 = m[&shirabe_php_shim::CaptureKey::ByIndex(0)]