From a726a3f461690d85bfebfab91c5af794b2f27f6d Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Mon, 2 Mar 2026 19:22:07 +0000
Subject: [PATCH] fix(parser): expand variables in [[ =~ $var ]] regex patterns

When regex pattern after =~ operator contains a variable reference ($),
use parse_word() for proper expansion instead of collect_conditional_regex_pattern()
which creates literal words. Literal regex patterns (without $) still use
the special collector to preserve parens, backslashes, etc.

Closes #400

https://claude.ai/code/session_01WZjYqxm5xMPAEe7FSHJkDy
---
 crates/bashkit/src/interpreter/mod.rs | 22 ++++++++++++++++++++++
 crates/bashkit/src/parser/mod.rs      | 16 +++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/crates/bashkit/src/interpreter/mod.rs b/crates/bashkit/src/interpreter/mod.rs
index 81a534b3..f36b208f 100644
--- a/crates/bashkit/src/interpreter/mod.rs
+++ b/crates/bashkit/src/interpreter/mod.rs
@@ -9727,4 +9727,26 @@ echo "count=$COUNT"
         let result = bash.exec(r#"printf "a\nb\nc" | wc -l"#).await.unwrap();
         assert_eq!(result.stdout.trim(), "2");
     }
+
+    #[tokio::test]
+    async fn test_regex_match_from_variable() {
+        // Issue #400: [[ =~ $var ]] should work with regex from variable
+        let mut bash = crate::Bash::new();
+        let result = bash
+            .exec(r#"re="200"; line="hello 200 world"; [[ $line =~ $re ]] && echo "match" || echo "no""#)
+            .await
+            .unwrap();
+        assert_eq!(result.stdout.trim(), "match");
+    }
+
+    #[tokio::test]
+    async fn test_regex_match_literal() {
+        // Issue #400: literal regex should still work
+        let mut bash = crate::Bash::new();
+        let result = bash
+            .exec(r#"line="hello 200 world"; [[ $line =~ 200 ]] && echo "match" || echo "no""#)
+            .await
+            .unwrap();
+        assert_eq!(result.stdout.trim(), "match");
+    }
 }
diff --git a/crates/bashkit/src/parser/mod.rs b/crates/bashkit/src/parser/mod.rs
index 3a3bebcb..3270f0d6 100644
--- a/crates/bashkit/src/parser/mod.rs
+++ b/crates/bashkit/src/parser/mod.rs
@@ -1263,10 +1263,20 @@ impl<'a> Parser<'a> {
                     let is_literal =
                         matches!(self.current_token, Some(tokens::Token::LiteralWord(_)));
 
-                    // After =~, collect the regex pattern (may contain parens)
+                    // After =~, handle regex pattern.
+                    // If the pattern contains $ (variable reference), parse it as a
+                    // normal word so variables expand. Otherwise collect as literal
+                    // regex to preserve parens, backslashes, etc.
                     if saw_regex_op {
-                        let pattern = self.collect_conditional_regex_pattern(&w_clone);
-                        words.push(Word::literal(&pattern));
+                        if w_clone.contains('$') && !is_quoted {
+                            // Variable reference — parse normally for expansion
+                            let parsed = self.parse_word(w_clone);
+                            words.push(parsed);
+                            self.advance();
+                        } else {
+                            let pattern = self.collect_conditional_regex_pattern(&w_clone);
+                            words.push(Word::literal(&pattern));
+                        }
                         saw_regex_op = false;
                         continue;
                     }