From 789bea635f6b566af6d2793fee484ce129c33caa Mon Sep 17 00:00:00 2001
From: Jonas Maier <jonas@x77.dev>
Date: Sun, 31 May 2026 19:36:01 +0200
Subject: comment parsing

---
 src/parse/mod.rs              | 20 +++++++++++++++++++-
 test-cases/comment/script.sh  |  6 ++++++
 test-cases/comment/stdout.txt |  1 +
 tests/scripts.rs              |  5 +++++
 4 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 test-cases/comment/script.sh
 create mode 100644 test-cases/comment/stdout.txt

diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 5815730..b475943 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -1537,8 +1537,26 @@ impl<'a> Cursor<'a> {
         matches!(self.buf[0], b' ' | b'\t' | b'\n' | b'\r')
     }
 
+    fn peek_comment(&self) -> bool {
+        self.has() && self.peek() == b'#'
+    }
+
+    fn consume_comment(&mut self) {
+        assert_eq!(self.adv(), b'#');
+        while self.has() && self.peek() != b'\n' {
+            self.adv();
+        }
+    }
+
     fn spaces(&mut self) {
-        while self.peek_space() {
+        while {
+            if self.peek_comment() {
+                self.consume_comment();
+                true
+            } else {
+                self.peek_space()
+            }
+        } {
             self.adv();
             self.spaced = true;
         }
diff --git a/test-cases/comment/script.sh b/test-cases/comment/script.sh
new file mode 100644
index 0000000..5f51002
--- /dev/null
+++ b/test-cases/comment/script.sh
@@ -0,0 +1,6 @@
+set X = good
+fun mutate {
+    set X = bad
+}
+# if this were not a comment, command interpolations would be executed: $(mutate)
+echo $X
diff --git a/test-cases/comment/stdout.txt b/test-cases/comment/stdout.txt
new file mode 100644
index 0000000..12799cc
--- /dev/null
+++ b/test-cases/comment/stdout.txt
@@ -0,0 +1 @@
+good
diff --git a/tests/scripts.rs b/tests/scripts.rs
index 9503d8c..93034c4 100644
--- a/tests/scripts.rs
+++ b/tests/scripts.rs
@@ -6,6 +6,11 @@ fn case0() {
     common::test_case("case0", include_bytes!("../test-cases/case0/script.sh"), include_bytes!("../test-cases/case0/stdout.txt"));
 }
 
+#[test]
+fn comment() {
+    common::test_case("comment", include_bytes!("../test-cases/comment/script.sh"), include_bytes!("../test-cases/comment/stdout.txt"));
+}
+
 #[test]
 fn fun0() {
     common::test_case("fun0", include_bytes!("../test-cases/fun0/script.sh"), include_bytes!("../test-cases/fun0/stdout.txt"));
-- 
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