refactor(preg): report unmatched groups as null throughout

The shim carried two reporting modes for the preg_* $matches maps: PHP's
default (trailing unmatched groups dropped, interior ones ""), and the
PREG_UNMATCHED_AS_NULL form, picked by calling a *_unmatched_as_null()
variant. The regex crate hands out Option<Match>, which maps onto the
null form directly, and no caller distinguished a dropped group from a
null one -- preg_match() and preg_match_all2() already reported nulls
unconditionally. Keep only the null form; the shim API no longer mirrors
PHP's flag set, which is intended.

Preg::is_match_with_indexed_captures() modelled PHP's "unset" as a
truncated Vec<String>, and now returns Vec<Option<String>>. That is what
Composer actually does: Preg::isMatch() always sets
PREG_UNMATCHED_AS_NULL, and its callers test groups with `!== null`.

preg_match_all(), preg_match_all_set_order() and
preg_split_delim_capture() still hand back Vec<String> and keep the ""
form.

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

2 files changed, 3 insertions, 5 deletions

diff --git a/crates/shirabe/src/command/fund_command.rs b/crates/shirabe/src/command/fund_command.rs
index 7f2dd24c..109943d6 100644
--- a/crates/shirabe/src/command/fund_command.rs
+++ b/crates/shirabe/src/command/fund_command.rs
@@ -67,7 +67,7 @@ impl FundCommand {
                     php_regex!(r"{^https://github.com/([^/]+)$}"),
                     &url,
                 )
-                && let Some(sponsor) = matches.into_iter().nth(1)
+                && let Some(sponsor) = matches.into_iter().nth(1).flatten()
             {
                 url = format!("https://github.com/sponsors/{}", sponsor);
             }
diff --git a/crates/shirabe/src/command/update_command.rs b/crates/shirabe/src/command/update_command.rs
index 38a79e30..2eca6db7 100644
--- a/crates/shirabe/src/command/update_command.rs
+++ b/crates/shirabe/src/command/update_command.rs
@@ -466,10 +466,8 @@ impl Command for UpdateCommand {
                 let Some(matches) = matches else {
                     continue;
                 };
-                let constraint = parser.parse_constraints(&format!(
-                    "~{}",
-                    matches.get(1).cloned().unwrap_or_default()
-                ))?;
+                let constraint = parser
+                    .parse_constraints(&format!("~{}", matches[1].clone().unwrap_or_default()))?;
                 if let Some(existing) = temporary_constraints.get(&package.get_name()) {
                     temporary_constraints.insert(
                         package.get_name(),