feat: string ops, read -r, heredoc tests (#237)

## Summary
- Implement `${s/#pat/repl}` prefix-anchored and `${s/%pat/repl}`
suffix-anchored pattern replacement
- Implement `${var:?"msg"}` error expansion with exit code 1
- Handle `\/` escape in pattern replacement parsing
- Add `read` builtin `-r` flag (raw mode) and `-p` flag parsing
- Add 31 new bash spec tests across 3 new test files (heredoc,
string-ops, read-builtin)
- Bash spec tests: 741 total, 735 pass, 6 skip (100% pass rate)
- Bash comparison: 668/668 match real bash (100%)

## Test plan
- [x] `cargo test --all-features` passes
- [x] `cargo clippy --all-targets --all-features -- -D warnings` clean
- [x] `cargo fmt --check` clean
- [x] Bash spec tests: 741 total, 0 failures
- [x] Bash comparison: 668/668 match (100%)

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

Author: chaliy

crates/bashkit/src/builtins/read.rs

@@ -18,21 +18,61 @@ impl Builtin for Read {
             None => return Ok(ExecResult::err("", 1)),
         };
 
+        // Parse flags
+        let mut raw_mode = false; // -r: don't interpret backslashes
+        let mut prompt = None::<String>; // -p prompt
+        let mut var_args = Vec::new();
+        let mut args_iter = ctx.args.iter();
+        while let Some(arg) = args_iter.next() {
+            if arg.starts_with('-') && arg.len() > 1 {
+                for flag in arg[1..].chars() {
+                    match flag {
+                        'r' => raw_mode = true,
+                        'p' => {
+                            // -p takes next arg as prompt
+                            if let Some(p) = args_iter.next() {
+                                prompt = Some(p.clone());
+                            }
+                        }
+                        _ => {} // ignore unknown flags
+                    }
+                }
+            } else {
+                var_args.push(arg.as_str());
+            }
+        }
+        let _ = prompt; // prompt is for interactive use, ignored in non-interactive
+
         // Get first line
-        let line = input.lines().next().unwrap_or("");
+        let line = if raw_mode {
+            // -r: treat backslashes literally
+            input.lines().next().unwrap_or("").to_string()
+        } else {
+            // Without -r: handle backslash line continuation
+            let mut result = String::new();
+            for l in input.lines() {
+                if let Some(stripped) = l.strip_suffix('\\') {
+                    result.push_str(stripped);
+                } else {
+                    result.push_str(l);
+                    break;
+                }
+            }
+            result
+        };
 
         // If no variable names given, use REPLY
-        let var_names: Vec<&str> = if ctx.args.is_empty() {
+        let var_names: Vec<&str> = if var_args.is_empty() {
             vec!["REPLY"]
         } else {
-            ctx.args.iter().map(|s| s.as_str()).collect()
+            var_args
         };
 
         // Split line by IFS (default: space, tab, newline)
         let ifs = ctx.env.get("IFS").map(|s| s.as_str()).unwrap_or(" \t\n");
         let words: Vec<&str> = if ifs.is_empty() {
             // Empty IFS means no word splitting
-            vec![line]
+            vec![&line]
         } else {
             line.split(|c: char| ifs.contains(c))
                 .filter(|s| !s.is_empty())

crates/bashkit/src/interpreter/mod.rs

@@ -4076,7 +4076,12 @@ impl Interpreter {
             ParameterOp::Error => {
                 // ${var:?error} - error if unset/empty
                 if value.is_empty() {
-                    // In real bash this would exit, we just return empty
+                    let msg = if operand.is_empty() {
+                        format!("bash: {}: parameter null or not set\n", name)
+                    } else {
+                        format!("bash: {}: {}\n", name, operand)
+                    };
+                    self.nounset_error = Some(msg);
                     String::new()
                 } else {
                     value.to_string()
@@ -4151,6 +4156,43 @@ impl Interpreter {
             return value.to_string();
         }
 
+        // Handle # prefix anchor (match at start only)
+        if let Some(rest) = pattern.strip_prefix('#') {
+            if rest.is_empty() {
+                return value.to_string();
+            }
+            if let Some(stripped) = value.strip_prefix(rest) {
+                return format!("{}{}", replacement, stripped);
+            }
+            // Try glob match at prefix
+            if rest.contains('*') {
+                let matched = self.remove_pattern(value, rest, true, false);
+                if matched != value {
+                    let prefix_len = value.len() - matched.len();
+                    return format!("{}{}", replacement, &value[prefix_len..]);
+                }
+            }
+            return value.to_string();
+        }
+
+        // Handle % suffix anchor (match at end only)
+        if let Some(rest) = pattern.strip_prefix('%') {
+            if rest.is_empty() {
+                return value.to_string();
+            }
+            if let Some(stripped) = value.strip_suffix(rest) {
+                return format!("{}{}", stripped, replacement);
+            }
+            // Try glob match at suffix
+            if rest.contains('*') {
+                let matched = self.remove_pattern(value, rest, false, false);
+                if matched != value {
+                    return format!("{}{}", matched, replacement);
+                }
+            }
+            return value.to_string();
+        }
+
         // Handle glob pattern with *
         if pattern.contains('*') {
             // Convert glob to regex-like behavior

crates/bashkit/src/parser/mod.rs

@@ -2231,12 +2231,24 @@ impl<'a> Parser<'a> {
                                     } else {
                                         false
                                     };
-                                    // Read pattern until /
+                                    // Read pattern until / (handle \/ as escaped /)
                                     let mut pattern = String::new();
                                     while let Some(&ch) = chars.peek() {
                                         if ch == '/' || ch == '}' {
                                             break;
                                         }
+                                        if ch == '\\' {
+                                            chars.next(); // consume backslash
+                                            if let Some(&next) = chars.peek() {
+                                                if next == '/' {
+                                                    // \/ -> literal /
+                                                    pattern.push(chars.next().unwrap());
+                                                    continue;
+                                                }
+                                            }
+                                            pattern.push('\\');
+                                            continue;
+                                        }
                                         pattern.push(chars.next().unwrap());
                                     }
                                     // Read replacement if present

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

@@ -0,0 +1,84 @@
+### heredoc_basic
+cat <<EOF
+hello world
+EOF
+### expect
+hello world
+### end
+
+### heredoc_variable
+NAME=world
+cat <<EOF
+hello $NAME
+EOF
+### expect
+hello world
+### end
+
+### heredoc_braced_variable
+NAME=world
+cat <<EOF
+hello ${NAME}!
+EOF
+### expect
+hello world!
+### end
+
+### heredoc_command_subst
+cat <<EOF
+$(echo hello from cmd)
+EOF
+### expect
+hello from cmd
+### end
+
+### heredoc_arithmetic
+cat <<EOF
+result is $((2 + 3))
+EOF
+### expect
+result is 5
+### end
+
+### heredoc_quoted_delimiter
+NAME=world
+cat <<'EOF'
+hello $NAME
+EOF
+### expect
+hello $NAME
+### end
+
+### heredoc_multiline
+A=foo
+B=bar
+cat <<EOF
+first: $A
+second: $B
+third: literal
+EOF
+### expect
+first: foo
+second: bar
+third: literal
+### end
+
+### heredoc_to_file
+cat > /tmp/heredoc_out.txt <<EOF
+line one
+line two
+EOF
+cat /tmp/heredoc_out.txt
+### expect
+line one
+line two
+### end
+
+### heredoc_mixed_expansion
+X=42
+cat <<EOF
+value: $X, cmd: $(echo hi), math: $((X * 2))
+EOF
+### expect
+value: 42, cmd: hi, math: 84
+### end

crates/bashkit/tests/spec_cases/bash/read-builtin.test.sh

@@ -0,0 +1,44 @@
+### read_basic
+### bash_diff
+echo "hello" | read var; echo "$var"
+### expect
+hello
+### end
+
+### read_multiple_vars
+echo "one two three" | { read a b c; echo "$a $b $c"; }
+### expect
+one two three
+### end
+
+### read_ifs
+echo "a:b:c" | { IFS=: read x y z; echo "$x $y $z"; }
+### expect
+a b c
+### end
+
+### read_herestring
+read var <<< "from herestring"
+echo "$var"
+### expect
+from herestring
+### end
+
+### read_empty_input
+echo "" | { read var; echo ">${var}<"; }
+### expect
+><
+### end
+
+### read_r_flag
+read -r var <<< "hello\nworld"
+echo "$var"
+### expect
+hello\nworld
+### end
+
+### read_leftover
+echo "one two three four" | { read a b; echo "$a|$b"; }
+### expect
+one|two three four
+### end

crates/bashkit/tests/spec_cases/bash/string-ops.test.sh

@@ -0,0 +1,99 @@
+### string_replace_prefix
+s="/usr/local/bin"
+echo "${s/#\/usr/PREFIX}"
+### expect
+PREFIX/local/bin
+### end
+
+### string_replace_suffix
+s="hello.txt"
+echo "${s/%.txt/.md}"
+### expect
+hello.md
+### end
+
+### string_default_colon
+echo "${UNSET_VAR:-fallback}"
+### expect
+fallback
+### end
+
+### string_default_empty
+X=""
+echo "${X:-fallback}"
+### expect
+fallback
+### end
+
+### string_error_message
+### bash_diff
+### exit_code:1
+${UNSET_VAR:?"variable not set"}
+### expect
+### end
+
+### string_use_replacement
+X="present"
+echo "${X:+replacement}"
+### expect
+replacement
+### end
+
+### string_use_replacement_empty
+EMPTY=""
+result="${EMPTY:+replacement}"
+echo ">${result}<"
+### expect
+><
+### end
+
+### string_length_unicode
+X="hello"
+echo "${#X}"
+### expect
+5
+### end
+
+### string_nested_expansion
+A="world"
+B="A"
+echo "${!B}"
+### expect
+world
+### end
+
+### string_concatenation
+A="hello"
+B="world"
+echo "${A} ${B}"
+### expect
+hello world
+### end
+
+### string_uppercase_pattern
+X="hello world"
+echo "${X^^}"
+### expect
+HELLO WORLD
+### end
+
+### string_lowercase_pattern
+X="HELLO WORLD"
+echo "${X,,}"
+### expect
+hello world
+### end
+
+### var_negative_substring
+X="hello world"
+echo "${X: -5}"
+### expect
+world
+### end
+
+### var_substring_length
+X="hello world"
+echo "${X:0:5}"
+### expect
+hello
+### end