From fa0bd722b72460306263fa97fd5a957b4d7ef8fd Mon Sep 17 00:00:00 2001
From: Joseph Jon Booker <joe@neoturbine.net>
Date: Wed, 27 Mar 2024 22:28:41 -0500
Subject: [PATCH] expr: Allow initial asterisk in regular expressions

GNU expr appears to treat this as a literal asterisk
---
 src/uu/expr/src/syntax_tree.rs | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/uu/expr/src/syntax_tree.rs b/src/uu/expr/src/syntax_tree.rs
index 7036ec010..da5b2ccc5 100644
--- a/src/uu/expr/src/syntax_tree.rs
+++ b/src/uu/expr/src/syntax_tree.rs
@@ -140,7 +140,8 @@ impl StringOp {
                 let left = left.eval()?.eval_as_string();
                 let right = right.eval()?.eval_as_string();
                 validate_regex(&right)?;
-                let re_string = format!("^{right}");
+                let prefix = if right.starts_with('*') { r"^\" } else { "^" };
+                let re_string = format!("{prefix}{right}");
                 let re = Regex::with_options(
                     &re_string,
                     RegexOptions::REGEX_OPTION_NONE,
@@ -681,6 +682,21 @@ mod test {
         assert_eq!(result.eval_as_string(), "");
     }
 
+    #[test]
+    fn starting_stars_become_escaped() {
+        let result = AstNode::parse(&["yolo", ":", r"*yolo"])
+            .unwrap()
+            .eval()
+            .unwrap();
+        assert_eq!(result.eval_as_string(), "0");
+
+        let result = AstNode::parse(&["*yolo", ":", r"*yolo"])
+            .unwrap()
+            .eval()
+            .unwrap();
+        assert_eq!(result.eval_as_string(), "5");
+    }
+
     #[test]
     fn validate_regex_valid() {
         assert!(validate_regex(r"(a+b) \(a* b\)").is_ok());