From 6d5d57d9dd4a558b8e1d6501f6e4ffc0f340c283 Mon Sep 17 00:00:00 2001
From: Jonas Maier <jonas@x77.dev>
Date: Wed, 18 Mar 2026 12:00:02 +0100
Subject: new string delimiter parsing

---
 src/parse/mod.rs | 134 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)

diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 0322c39..172974c 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -522,6 +522,140 @@ impl Parse for VarName {
     }
 }
 
+#[derive(Clone)]
+enum StringDelimiter {
+    /// no delimiter, i.e. when parsing a simple command like `echo foo`
+    None,
+
+    /// double quotes, allows interpolation, `echo "foo $var"`
+    Interp,
+
+    /// single quotes, does not allow interpolation `echo 'foo $vardoesnotexpand'`
+    Strict,
+
+    /// triple quotes with custom prefix/suffix ```
+    /// echo DELIM"""
+    /// basically
+    /// a
+    /// heredoc
+    /// with
+    /// $variables
+    /// """DELIM
+    /// ```
+    InterpCustom(BString),
+
+    /// triple single quotes with custom prefix/suffix ```
+    /// echo FOO'''
+    /// basically
+    /// a
+    /// heredoc
+    /// without
+    /// variables
+    /// '''FOO
+    /// ```
+    StrictCustom(BString),
+}
+
+/// gets the largest ident this slice starts with, might be empty
+fn peek_ident(b: &[u8]) -> &[u8] {
+    if b.is_empty() || !b[0].is_ascii_alphabetic() {
+        return &[];
+    }
+
+    let mut out = &b[..1];
+
+    for i in 1..b.len() {
+        if b[i].is_ascii_alphanumeric() {
+            out = &b[..=i];
+        } else {
+            break;
+        }
+    }
+
+    out
+}
+
+impl StringDelimiter {
+    fn try_begin(b: &mut Cursor<'_>) -> Option<Self> {
+        if !b.has() {
+            return None;
+        }
+
+        let ident = peek_ident(&b.buf);
+        if b.buf[ident.len()..].starts_with(b"\"\"\"") {
+            b.advance(ident.len() + 3);
+            return Some(Self::InterpCustom(ident.to_vec()));
+        }
+        if b.buf[ident.len()..].starts_with(b"'''") {
+            b.advance(ident.len() + 3);
+            return Some(Self::StrictCustom(ident.to_vec()));
+        }
+
+        // at this point we know it's not a custom identifier with triple quotes
+
+        let x = b.peek();
+
+        if !x.is_ascii_whitespace() && (!is_symbol(x) || x == b'$') {
+            return Some(Self::None);
+        }
+
+        if x == b'"' {
+            b.adv();
+            return Some(Self::Interp);
+        }
+
+        if x == b'\'' {
+            b.adv();
+            return Some(Self::Strict);
+        }
+
+        None
+    }
+
+    /// if the current string ends right at the cursor, consumes the string closing tokens and returns true
+    /// otherwise, consumes no tokens and returns false
+    fn try_end(&self, b: &mut Cursor<'_>) -> bool {
+        if !b.has() {
+            return false;
+        }
+
+        let x = b.peek();
+        let buf = &mut b.buf;
+
+        match self {
+            StringDelimiter::None if x.is_ascii_whitespace() || is_symbol(x) && x != b'$' => {
+                b.adv();
+                true
+            }
+            StringDelimiter::Interp if x == b'"' => {
+                b.adv();
+                true
+            }
+            StringDelimiter::Strict if x == b'\'' => {
+                b.adv();
+                true
+            }
+            StringDelimiter::InterpCustom(delim)
+                if buf.len() >= 3 && &buf[..3] == b"\"\"\"" && buf[3..].starts_with(&delim) =>
+            {
+                b.advance(3 + delim.len());
+                true
+            }
+            StringDelimiter::StrictCustom(delim)
+                if buf.len() >= 3 && &buf[..3] == b"'''" && buf[3..].starts_with(&delim) =>
+            {
+                b.advance(3 + delim.len());
+                true
+            }
+            _ => false,
+        }
+    }
+
+    fn is_strict(&self) -> bool {
+        matches!(self, Self::Strict | Self::StrictCustom(_))
+    }
+}
+
 impl Parse for ExpString {
     fn parse(b: &mut Cursor<'_>) -> Result<Self> {
         b.spaces();
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