refactor(preg): merge preg_match_all_offset_capture2() into its sibling

The two functions ran the same search and differed only in how they
reported a non-participating group: one as ("", 0) in a bespoke struct,
the other as (null, -1) in a capture-key map. Neither shape covered both
callers, because PHP reaches preg_match_all() with different flags from
each: Preg::matchAllWithOffsets() always ORs in PREG_UNMATCHED_AS_NULL,
while OutputFormatter::formatAndWrap() passes PREG_OFFSET_CAPTURE alone.

Keep the capture-key map, which also exposes named groups, and take the
flags that decide between null and "" for an unmatched group. The offset
is -1 either way, so the ("", 0) approximation is gone.

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

1 files changed, 6 insertions, 40 deletions

diff --git a/crates/shirabe-php-shim/src/preg.rs b/crates/shirabe-php-shim/src/preg.rs
index 40eb25fb..c762cb95 100644
--- a/crates/shirabe-php-shim/src/preg.rs
+++ b/crates/shirabe-php-shim/src/preg.rs
@@ -15,17 +15,6 @@ pub enum CaptureKey {
     ByName(String),
 }
 
-#[derive(Debug, Default)]
-pub struct PregOffsetCaptureMatches {
-    groups: Vec<Vec<(String, usize)>>,
-}
-
-impl PregOffsetCaptureMatches {
-    pub fn group(&self, i: usize) -> &[(String, usize)] {
-        &self.groups[i]
-    }
-}
-
 pub fn preg_quote(str: &str, delimiter: Option<char>) -> String {
     // Regex pattern compatibility:
     // PHP's preg_quote escapes `<` and `>` (PCRE treats `\<`/`\>` as literals), but the `regex`
@@ -171,38 +160,12 @@ pub fn preg_match_all_set_order(
 pub fn preg_match_all_offset_capture(
     pattern: impl PregPattern,
     subject: &str,
-    matches: &mut PregOffsetCaptureMatches,
-) -> usize {
-    let __resolved = pattern.resolve();
-    let (re, _anchored) = __resolved.parts();
-    let group_count = re.captures_len();
-    matches.groups = vec![Vec::new(); group_count];
-
-    let mut count = 0;
-    for caps in re.captures_iter(subject) {
-        count += 1;
-        for g in 0..group_count {
-            // PHP stores ["", -1] for non-participating groups under
-            // PREG_OFFSET_CAPTURE; the unsigned offset here approximates -1 as 0,
-            // which callers must not rely on for absent groups.
-            let entry = caps
-                .get(g)
-                .map(|m| (m.as_str().to_string(), m.start()))
-                .unwrap_or_else(|| (String::new(), 0));
-            matches.groups[g].push(entry);
-        }
-    }
-
-    count
-}
-
-pub fn preg_match_all_offset_capture2(
-    pattern: impl PregPattern,
-    subject: &str,
     matches: &mut indexmap::IndexMap<CaptureKey, Vec<(Option<String>, i64)>>,
+    flags: i64,
 ) -> 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();
 
@@ -211,9 +174,12 @@ pub fn preg_match_all_offset_capture2(
     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 => (None, -1),
+                None if unmatched_as_null => (None, -1),
+                None => (Some(String::new()), -1),
             };
             column.push(entry);
         }