Reverse search with a long prompt followed by ctrl-c causes an assertion failure panic

[nicklan]

You can cause a panic with the following:

1. set a prompt of at least 35 characters
2. initiate a reverse search (ctrl-r)
3. type something
4. hit ctrl-c

Here's the backtrace:

(failed reverse-i-search)`okef': eokf  thread 'main' panicked at 'assertion failed: self.layout.cursor <= self.layout.end', /home/user/rustyline/src/edit.rs:128:13
stack backtrace:
   0: rust_begin_unwind
             at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/panicking.rs:517:5
   1: core::panicking::panic_fmt
             at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:100:14
   2: core::panicking::panic
             at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:50:5
   3: rustyline::edit::State<H>::move_cursor
             at ./src/edit.rs:128:13
   4: rustyline::edit::State<H>::edit_move_buffer_end
             at ./src/edit.rs:465:13
   5: rustyline::command::execute
             at ./src/command.rs:225:13
   6: rustyline::readline_edit
             at ./src/lib.rs:537:15
   7: rustyline::readline_raw
             at ./src/lib.rs:572:22
   8: rustyline::Editor<H>::readline_with
             at ./src/lib.rs:784:13
   9: rustyline::Editor<H>::readline
             at ./src/lib.rs:760:9
  10: example::main
             at ./examples/example.rs:108:24
  11: core::ops::function::FnOnce::call_once
             at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

This is just a slightly modified version of the example.rs example:

use std::borrow::Cow::{self, Borrowed, Owned};

use rustyline::completion::{Completer, FilenameCompleter, Pair};
use rustyline::config::OutputStreamType;
use rustyline::error::ReadlineError;
use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
use rustyline::hint::{Hinter, HistoryHinter};
use rustyline::validate::{self, MatchingBracketValidator, Validator};
use rustyline::{Cmd, CompletionType, Config, Context, EditMode, Editor, KeyEvent};
use rustyline_derive::Helper;

#[derive(Helper)]
struct MyHelper {
    completer: FilenameCompleter,
    highlighter: MatchingBracketHighlighter,
    validator: MatchingBracketValidator,
    hinter: HistoryHinter,
    colored_prompt: String,
}

impl Completer for MyHelper {
    type Candidate = Pair;

    fn complete(
        &self,
        line: &str,
        pos: usize,
        ctx: &Context<'_>,
    ) -> Result<(usize, Vec<Pair>), ReadlineError> {
        self.completer.complete(line, pos, ctx)
    }
}

impl Hinter for MyHelper {
    type Hint = String;

    fn hint(&self, line: &str, pos: usize, ctx: &Context<'_>) -> Option<String> {
        self.hinter.hint(line, pos, ctx)
    }
}

impl Highlighter for MyHelper {
    fn highlight_prompt<'b, 's: 'b, 'p: 'b>(
        &'s self,
        prompt: &'p str,
        default: bool,
    ) -> Cow<'b, str> {
        if default {
            Borrowed(&self.colored_prompt)
        } else {
            Borrowed(prompt)
        }
    }

    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
        Owned("\x1b[1m".to_owned() + hint + "\x1b[m")
    }

    fn highlight<'l>(&self, line: &'l str, pos: usize) -> Cow<'l, str> {
        self.highlighter.highlight(line, pos)
    }

    fn highlight_char(&self, line: &str, pos: usize) -> bool {
        self.highlighter.highlight_char(line, pos)
    }
}

impl Validator for MyHelper {
    fn validate(
        &self,
        ctx: &mut validate::ValidationContext,
    ) -> rustyline::Result<validate::ValidationResult> {
        self.validator.validate(ctx)
    }

    fn validate_while_typing(&self) -> bool {
        self.validator.validate_while_typing()
    }
}

// To debug rustyline:
// RUST_LOG=rustyline=debug cargo run --example example 2> debug.log
fn main() -> rustyline::Result<()> {
    env_logger::init();
    let config = Config::builder()
        .history_ignore_space(true)
        .completion_type(CompletionType::List)
        .edit_mode(EditMode::Emacs)
        .output_stream(OutputStreamType::Stdout)
        .build();
    let h = MyHelper {
        completer: FilenameCompleter::new(),
        highlighter: MatchingBracketHighlighter::new(),
        hinter: HistoryHinter {},
        colored_prompt: "".to_owned(),
        validator: MatchingBracketValidator::new(),
    };
    let mut rl = Editor::with_config(config);
    rl.set_helper(Some(h));
    rl.bind_sequence(KeyEvent::alt('n'), Cmd::HistorySearchForward);
    rl.bind_sequence(KeyEvent::alt('p'), Cmd::HistorySearchBackward);
    if rl.load_history("history.txt").is_err() {
        println!("No previous history.");
    }
    loop {
        let p = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>";
        rl.helper_mut().expect("No helper").colored_prompt = format!("\x1b[1;32m{}\x1b[0m", p);
        let readline = rl.readline(&p);
        match readline {
            Ok(line) => {
                rl.add_history_entry(line.as_str());
                println!("Line: {}", line);
            }
            Err(ReadlineError::Interrupted) => {
                println!("CTRL-C");
                break;
            }
            Err(ReadlineError::Eof) => {
                println!("CTRL-D");
                break;
            }
            Err(err) => {
                println!("Error: {:?}", err);
                break;
            }
        }
    }
    rl.append_history("history.txt")
}

[gwenn]

use rustyline::{Editor, Result};

fn main() -> Result<()> {
    let mut rl = Editor::<()>::new();
    loop {
        let line = rl.readline("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>")?;
        rl.add_history_entry(line.as_str());
    }
}

rustyline % cargo run --example minimal
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>line1
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>line2
(reverse-i-search)`e': line2            thread 'main' panicked at 'assertion failed: self.layout.cursor <= self.layout.end', /Users/gwen/Rust/rustyline/src/edit.rs:128:13

[gwenn]

We try to move cursor to the end of line (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>line2) but this is not the actual line during reverse search ((reverse-i-search)e': line2`):

layout = {rustyline::layout::Layout} 
 prompt_size = {rustyline::layout::Position} 
  col = {usize} 35
  row = {usize} 0
 default_prompt = {bool} false
 cursor = {rustyline::layout::Position} 
  col = {usize} 40 -- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa>line2
  row = {usize} 0
 end = {rustyline::layout::Position} 
  col = {usize} 28 -- (reverse-i-search)`e': line2
  row = {usize} 0

[gwenn]

Thanks for the detailed bug report.
Could you please give #576 a try ?

[gwenn]

Version 9.1.0 released.

[nicklan]

Thanks for the quick fix! It sorted out my problem.