refactor(preg): report unmatched groups as null in the vec-shaped preg_*

preg_match_all() and preg_match_all_set_order() were the last preg_*
functions handing back a bare Vec<String>, where a group that did not
participate is indistinguishable from one that captured "". Hand back
Option<String> as the map-shaped functions already do; php_match_row(),
the last of the truncate-then-pad helpers, goes with them.

preg_split_delim_capture() keeps its Vec<String>. preg_split() accepts
no PREG_UNMATCHED_AS_NULL, so there is no null form to move it to, and
its result interleaves split segments -- which can never be absent --
with the captured delimiters.

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

2 files changed, 25 insertions, 4 deletions

diff --git a/crates/shirabe-symfony-console/src/completion/completion_input.rs b/crates/shirabe-symfony-console/src/completion/completion_input.rs
index 2f146a39..aafa7c8a 100644
--- a/crates/shirabe-symfony-console/src/completion/completion_input.rs
+++ b/crates/shirabe-symfony-console/src/completion/completion_input.rs
@@ -34,7 +34,17 @@ impl CompletionInput {
             input_str,
         );
 
-        Self::from_tokens(tokens[0].clone(), current_index)
+        Self::from_tokens(
+            tokens[0]
+                .iter()
+                .map(|token| {
+                    token
+                        .clone()
+                        .expect("group 0 participates whenever the pattern matches")
+                })
+                .collect(),
+            current_index,
+        )
     }
 
     /// Create an input based on an COMP_WORDS token list.
diff --git a/crates/shirabe-symfony-console/src/formatter/output_formatter.rs b/crates/shirabe-symfony-console/src/formatter/output_formatter.rs
index 311d50fd..c7c06cf5 100644
--- a/crates/shirabe-symfony-console/src/formatter/output_formatter.rs
+++ b/crates/shirabe-symfony-console/src/formatter/output_formatter.rs
@@ -109,7 +109,7 @@ impl OutputFormatter {
             return Ok(Some(style.borrow().clone_box()));
         }
 
-        let mut matches: Vec<Vec<String>> = vec![];
+        let mut matches: Vec<Vec<Option<String>>> = vec![];
         if preg_match_all_set_order(php_regex!("/([^=]+)=([^;]+)(;|$)/"), string, &mut matches) == 0
         {
             return Ok(None);
@@ -117,7 +117,14 @@ impl OutputFormatter {
 
         let mut style = OutputFormatterStyle::new(None, None, vec![]);
         for r#match in &matches {
-            let mut r#match: Vec<String> = r#match.clone();
+            let mut r#match: Vec<String> = r#match
+                .iter()
+                .map(|group| {
+                    group
+                        .clone()
+                        .expect("every group participates whenever the pattern matches")
+                })
+                .collect();
             shirabe_php_shim::array_shift(&mut r#match);
             r#match[0] = shirabe_php_shim::strtolower(&r#match[0]);
 
@@ -135,7 +142,11 @@ impl OutputFormatter {
                 );
                 let options = shirabe_php_shim::array_shift(&mut options).unwrap_or_default();
                 for option in &options {
-                    style.set_option(option);
+                    style.set_option(
+                        option
+                            .as_deref()
+                            .expect("group 0 participates whenever the pattern matches"),
+                    );
                 }
             } else {
                 return Ok(None);