fix(interpreter): write heredoc content when redirected to file (#370)

## Summary

- Fix heredoc redirect to file (`cat <<EOF > file`) which previously
wrote to stdout instead of the file
- Lexer now captures rest-of-line text after heredoc delimiter instead
of discarding it
- Parser creates a sub-parser to extract additional redirects from the
rest-of-line

Closes #345

## Test plan

- [x] Added 3 new spec tests: `heredoc_redirect_after`,
`heredoc_redirect_after_with_vars`, `heredoc_redirect_after_multiline`
- [x] Added lexer unit test `test_read_heredoc_with_redirect`
- [x] All 1308 bash spec tests pass (100% pass rate)
- [x] Existing `heredoc_to_file` test (`cat > file <<EOF` syntax) still
passes
- [x] `cargo fmt --check` clean
- [x] `cargo clippy -- -D warnings` clean

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: chaliy

crates/bashkit/src/parser/lexer.rs

@@ -19,6 +19,9 @@ pub struct Lexer<'a> {
     /// Current position in the input
     position: Position,
     chars: std::iter::Peekable<std::str::Chars<'a>>,
+    /// Rest-of-line text captured during heredoc parsing.
+    /// In `cat <<EOF > file`, this holds ` > file`.
+    pub heredoc_rest_of_line: String,
 }
 
 impl<'a> Lexer<'a> {
@@ -28,6 +31,7 @@ impl<'a> Lexer<'a> {
             input,
             position: Position::new(),
             chars: input.chars().peekable(),
+            heredoc_rest_of_line: String::new(),
         }
     }
 
@@ -1208,12 +1212,16 @@ impl<'a> Lexer<'a> {
         let mut content = String::new();
         let mut current_line = String::new();
 
-        // Skip to end of current line first (after the delimiter on command line)
+        // Collect the rest of the command line after the heredoc delimiter.
+        // In bash, `cat <<EOF > file` means `> file` is still part of
+        // the command and should be parsed for redirections.
+        self.heredoc_rest_of_line.clear();
         while let Some(ch) = self.peek_char() {
             self.advance();
             if ch == '\n' {
                 break;
             }
+            self.heredoc_rest_of_line.push(ch);
         }
 
         // Read lines until we find the delimiter
@@ -1362,13 +1370,15 @@ mod tests {
         let mut lexer = Lexer::new("\nhello\nworld\nEOF");
         let content = lexer.read_heredoc("EOF");
         assert_eq!(content, "hello\nworld\n");
+        assert_eq!(lexer.heredoc_rest_of_line.trim(), "");
     }
 
     #[test]
     fn test_read_heredoc_single_line() {
         let mut lexer = Lexer::new("\ntest\nEOF");
         let content = lexer.read_heredoc("EOF");
         assert_eq!(content, "test\n");
+        assert_eq!(lexer.heredoc_rest_of_line.trim(), "");
     }
 
     #[test]
@@ -1384,6 +1394,18 @@ mod tests {
         // Now read heredoc content
         let content = lexer.read_heredoc("EOF");
         assert_eq!(content, "hello\nworld\n");
+        assert_eq!(lexer.heredoc_rest_of_line.trim(), "");
+    }
+
+    #[test]
+    fn test_read_heredoc_with_redirect() {
+        let mut lexer = Lexer::new("cat <<EOF > file.txt\nhello\nEOF");
+        assert_eq!(lexer.next_token(), Some(Token::Word("cat".to_string())));
+        assert_eq!(lexer.next_token(), Some(Token::HereDoc));
+        assert_eq!(lexer.next_token(), Some(Token::Word("EOF".to_string())));
+        let content = lexer.read_heredoc("EOF");
+        assert_eq!(content, "hello\n");
+        assert_eq!(lexer.heredoc_rest_of_line.trim(), "> file.txt");
     }
 
     #[test]

crates/bashkit/src/parser/mod.rs

@@ -1768,15 +1768,18 @@ impl<'a> Parser<'a> {
                     };
                     // Don't advance - let read_heredoc consume directly from lexer position
 
-                    // Read the here document content (reads until delimiter line)
+                    // Read the here document content (reads until delimiter line).
+                    // Also captures rest-of-line text (e.g. `> file` in
+                    // `cat <<EOF > file`) into lexer.heredoc_rest_of_line.
                     let content = self.lexer.read_heredoc(&delimiter);
+                    let rest_of_line = std::mem::take(&mut self.lexer.heredoc_rest_of_line);
 
                     // Strip leading tabs for <<-
                     let content = if strip_tabs {
                         let had_trailing_newline = content.ends_with('\n');
                         let mut stripped: String = content
                             .lines()
-                            .map(|l| l.trim_start_matches('\t'))
+                            .map(|l: &str| l.trim_start_matches('\t'))
                             .collect::<Vec<_>>()
                             .join("\n");
                         if had_trailing_newline {
@@ -1787,9 +1790,6 @@ impl<'a> Parser<'a> {
                         content
                     };
 
-                    // Now advance to get the next token after the heredoc
-                    self.advance();
-
                     // If delimiter was quoted, content is literal (no expansion)
                     // Otherwise, parse for variable expansion
                     let target = if quoted {
@@ -1810,6 +1810,54 @@ impl<'a> Parser<'a> {
                         target,
                     });
 
+                    // Parse rest-of-line for additional redirects
+                    // (e.g. `> file` in `cat <<EOF > file`).
+                    // We parse tokens directly instead of using parse_simple_command
+                    // because that method returns None for redirect-only input
+                    // (no command word), dropping the redirects we need.
+                    if !rest_of_line.trim().is_empty() {
+                        let mut sub = Parser::new(&rest_of_line);
+                        loop {
+                            match &sub.current_token {
+                                Some(tokens::Token::RedirectOut) => {
+                                    sub.advance();
+                                    if let Ok(target) = sub.expect_word() {
+                                        redirects.push(Redirect {
+                                            fd: None,
+                                            kind: RedirectKind::Output,
+                                            target,
+                                        });
+                                    }
+                                }
+                                Some(tokens::Token::RedirectAppend) => {
+                                    sub.advance();
+                                    if let Ok(target) = sub.expect_word() {
+                                        redirects.push(Redirect {
+                                            fd: None,
+                                            kind: RedirectKind::Append,
+                                            target,
+                                        });
+                                    }
+                                }
+                                Some(tokens::Token::RedirectFd(fd)) => {
+                                    let fd = *fd;
+                                    sub.advance();
+                                    if let Ok(target) = sub.expect_word() {
+                                        redirects.push(Redirect {
+                                            fd: Some(fd),
+                                            kind: RedirectKind::Output,
+                                            target,
+                                        });
+                                    }
+                                }
+                                _ => break,
+                            }
+                        }
+                    }
+
+                    // Now advance past the heredoc body
+                    self.advance();
+
                     // Heredoc body consumed subsequent lines from input.
                     // Stop parsing this command - next tokens belong to new commands.
                     break;

crates/bashkit/tests/spec_cases/bash/heredoc.test.sh

@@ -83,6 +83,44 @@ EOF
 value: 42, cmd: hi, math: 84
 ### end
 
+### heredoc_redirect_after
+# cat <<EOF > file should write heredoc content to file, not stdout
+cat <<EOF > /tmp/heredoc_redirect.txt
+line one
+line two
+EOF
+cat /tmp/heredoc_redirect.txt
+### expect
+line one
+line two
+### end
+
+### heredoc_redirect_after_with_vars
+# cat <<EOF > file with variable expansion
+NAME=world
+cat <<EOF > /tmp/heredoc_vars.txt
+hello $NAME
+EOF
+cat /tmp/heredoc_vars.txt
+### expect
+hello world
+### end
+
+### heredoc_redirect_after_multiline
+# cat <<EOF > file with multiline YAML-like content (issue #345)
+mkdir -p /tmp/app
+cat <<EOF > /tmp/app/config.yaml
+app:
+  name: myservice
+  port: 8080
+EOF
+cat /tmp/app/config.yaml
+### expect
+app:
+  name: myservice
+  port: 8080
+### end
+
 ### heredoc_tab_strip
 # <<- strips leading tabs from content and delimiter
 cat <<-EOF