Add Option for Prefix-Based Reverse Search

Allow history search via Arrow-Up/Down or C-p/n to go either line-by-line or based on the prefix before the cursor position

Fix #423

examples/example.rs

@@ -1,7 +1,7 @@
 use std::borrow::Cow::{self, Borrowed, Owned};
 
 use rustyline::completion::{Completer, FilenameCompleter, Pair};
-use rustyline::config::OutputStreamType;
+use rustyline::config::{HistorySearchBehaviour, OutputStreamType};
 use rustyline::error::ReadlineError;
 use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
 use rustyline::hint::{Hinter, HistoryHinter};
@@ -87,6 +87,7 @@ fn main() -> rustyline::Result<()> {
         .completion_type(CompletionType::List)
         .edit_mode(EditMode::Emacs)
         .output_stream(OutputStreamType::Stdout)
+        .history_search_behaviour(HistorySearchBehaviour::LineByLine)
         .build();
     let h = MyHelper {
         completer: FilenameCompleter::new(),

src/command.rs

@@ -104,8 +104,8 @@ pub fn execute<H: Helper>(
                 s.edit_history_next(false)?
             }
         }
-        Cmd::HistorySearchBackward => s.edit_history_search(Direction::Reverse)?,
-        Cmd::HistorySearchForward => s.edit_history_search(Direction::Forward)?,
+        Cmd::HistorySearchBackward => s.edit_history_search(Direction::Reverse, false)?,
+        Cmd::HistorySearchForward => s.edit_history_search(Direction::Forward, false)?,
         Cmd::TransposeChars => {
             // Exchange the char before cursor with the character at cursor.
             s.edit_transpose_chars()?

src/config.rs

@@ -34,6 +34,9 @@ pub struct Config {
     check_cursor_position: bool,
     /// Bracketed paste on unix platform
     enable_bracketed_paste: bool,
+    /// Whether Arrow-Up/Down and C-p/n should go through the history line-by-line or perform a
+    /// reverse-search with the current prefix before the cursor.
+    history_search_behaviour: HistorySearchBehaviour,
 }
 
 impl Config {
@@ -176,6 +179,21 @@ impl Config {
     pub fn enable_bracketed_paste(&self) -> bool {
         self.enable_bracketed_paste
     }
+
+    /// Whether Arrow-Up/Down and C-p/n should go through the history line-by-line or perform a
+    /// reverse-search with the current prefix before the cursor.
+    ///
+    /// By default, go through the history line-by-line.
+    pub fn history_search_behaviour(&self) -> HistorySearchBehaviour {
+        self.history_search_behaviour
+    }
+
+    pub(crate) fn set_history_search_behaviour(
+        &mut self,
+        history_search_behaviour: HistorySearchBehaviour,
+    ) {
+        self.history_search_behaviour = history_search_behaviour;
+    }
 }
 
 impl Default for Config {
@@ -196,6 +214,7 @@ impl Default for Config {
             indent_size: 2,
             check_cursor_position: false,
             enable_bracketed_paste: true,
+            history_search_behaviour: HistorySearchBehaviour::LineByLine,
         }
     }
 }
@@ -286,6 +305,17 @@ pub enum OutputStreamType {
     Stdout,
 }
 
+/// Control going through the history with Arrow-Up/Down and C-p/n
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum HistorySearchBehaviour {
+    /// Go backwards through the history line-by-line.
+    LineByLine,
+    /// Implicit reverse search: Only show history entries which start with the current prefix
+    /// before the cursor.
+    PrefixReverseSearch,
+}
+
 /// Configuration builder
 #[derive(Clone, Debug, Default)]
 pub struct Builder {
@@ -415,6 +445,18 @@ impl Builder {
         self
     }
 
+    /// Whether Arrow-Up/Down and C-p/n should go through the history line-by-line or perform a
+    /// reverse-search with the current prefix before the cursor.
+    ///
+    /// By default, go through the history line-by-line.
+    pub fn history_search_behaviour(
+        mut self,
+        history_search_behaviour: HistorySearchBehaviour,
+    ) -> Self {
+        self.set_history_search_behaviour(history_search_behaviour);
+        self
+    }
+
     /// Builds a `Config` with the settings specified so far.
     pub fn build(self) -> Config {
         self.p
@@ -529,4 +571,13 @@ pub trait Configurer {
     fn enable_bracketed_paste(&mut self, enabled: bool) {
         self.config_mut().enable_bracketed_paste = enabled;
     }
+
+    /// Whether Arrow-Up/Down and C-p/n should go through the history line-by-line or perform a
+    /// reverse-search with the current prefix before the cursor.
+    ///
+    /// By default, go through the history line-by-line.
+    fn set_history_search_behaviour(&mut self, history_search_behaviour: HistorySearchBehaviour) {
+        self.config_mut()
+            .set_history_search_behaviour(history_search_behaviour);
+    }
 }

src/edit.rs

@@ -8,6 +8,7 @@ use unicode_segmentation::UnicodeSegmentation;
 use unicode_width::UnicodeWidthChar;
 
 use super::{Context, Helper, Result};
+use crate::config::HistorySearchBehaviour;
 use crate::highlight::Highlighter;
 use crate::hint::Hint;
 use crate::history::Direction;
@@ -34,6 +35,7 @@ pub struct State<'out, 'prompt, H: Helper> {
     pub ctx: Context<'out>,          // Give access to history for `hinter`
     pub hint: Option<Box<dyn Hint>>, // last hint displayed
     highlight_char: bool,            // `true` if a char has been highlighted
+    history_search_behaviour: HistorySearchBehaviour, // search history line-by-line or prefix-based
 }
 
 enum Info<'m> {
@@ -48,6 +50,7 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
         prompt: &'prompt str,
         helper: Option<&'out H>,
         ctx: Context<'out>,
+        history_search_behaviour: HistorySearchBehaviour,
     ) -> State<'out, 'prompt, H> {
         let prompt_size = out.calculate_position(prompt, Position::default());
         State {
@@ -63,6 +66,7 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
             ctx,
             hint: None,
             highlight_char: false,
+            history_search_behaviour,
         }
     }
 
@@ -228,6 +232,12 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
             Ok(ValidationResult::Valid(None))
         }
     }
+
+    fn update_line(&mut self, buf: &str, pos: usize) {
+        self.changes.borrow_mut().begin();
+        self.line.update(buf, pos);
+        self.changes.borrow_mut().end();
+    }
 }
 
 impl<'out, 'prompt, H: Helper> Invoke for State<'out, 'prompt, H> {
@@ -581,25 +591,42 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
         } else if self.ctx.history_index == 0 && prev {
             return Ok(());
         }
-        if prev {
-            self.ctx.history_index -= 1;
-        } else {
-            self.ctx.history_index += 1;
-        }
-        if self.ctx.history_index < history.len() {
-            let buf = history.get(self.ctx.history_index).unwrap();
-            self.changes.borrow_mut().begin();
-            self.line.update(buf, buf.len());
-            self.changes.borrow_mut().end();
-        } else {
-            // Restore current edited line
-            self.restore();
+
+        match self.history_search_behaviour {
+            // only if we have a prefix, do a prefix reverse search
+            HistorySearchBehaviour::PrefixReverseSearch if self.line.pos() != 0 => {
+                let direction = if prev {
+                    Direction::Reverse
+                } else {
+                    Direction::Forward
+                };
+                self.edit_history_search(direction, true)?;
+            }
+            // if we don't have a prefix, just go forward / backward one history entry
+            HistorySearchBehaviour::LineByLine | HistorySearchBehaviour::PrefixReverseSearch => {
+                if prev {
+                    self.ctx.history_index -= 1;
+                } else {
+                    self.ctx.history_index += 1;
+                }
+                if self.ctx.history_index < history.len() {
+                    let buf = history.get(self.ctx.history_index).unwrap();
+                    let pos = match self.history_search_behaviour {
+                        HistorySearchBehaviour::LineByLine => buf.len(),
+                        HistorySearchBehaviour::PrefixReverseSearch => self.line.pos(),
+                    };
+                    self.update_line(buf, pos);
+                } else {
+                    // Restore current edited line
+                    self.restore();
+                }
+            }
         }
         self.refresh_line()
     }
 
     // Non-incremental, anchored search
-    pub fn edit_history_search(&mut self, dir: Direction) -> Result<()> {
+    pub fn edit_history_search(&mut self, dir: Direction, keep_cursor_pos: bool) -> Result<()> {
         let history = self.ctx.history;
         if history.is_empty() {
             return self.out.beep();
@@ -621,13 +648,28 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
         ) {
             self.ctx.history_index = history_index;
             let buf = history.get(history_index).unwrap();
-            self.changes.borrow_mut().begin();
-            self.line.update(buf, buf.len());
-            self.changes.borrow_mut().end();
-            self.refresh_line()
-        } else {
-            self.out.beep()
+
+            // if the history search results in the same command we found last, continue searching
+            // for a different command
+            if buf == self.line.as_str() {
+                return self.edit_history_search(dir, keep_cursor_pos);
+            }
+
+            let pos = if keep_cursor_pos {
+                self.line.pos()
+            } else {
+                buf.len()
+            };
+            self.update_line(buf, pos);
+        } else {
+            self.ctx.history_index = match dir {
+                Direction::Forward => history.len(),
+                Direction::Reverse => 0,
+            };
+            self.restore();
+            self.out.beep()?;
         }
+        self.refresh_line()
     }
 
     /// Substitute the currently edited line with the first/last history entry.
@@ -649,9 +691,7 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
         if first {
             self.ctx.history_index = 0;
             let buf = history.get(self.ctx.history_index).unwrap();
-            self.changes.borrow_mut().begin();
-            self.line.update(buf, buf.len());
-            self.changes.borrow_mut().end();
+            self.update_line(buf, buf.len());
         } else {
             self.ctx.history_index = history.len();
             // Restore current edited line
@@ -677,6 +717,7 @@ pub fn init_state<'out, H: Helper>(
     pos: usize,
     helper: Option<&'out H>,
     history: &'out crate::history::History,
+    history_search_behaviour: HistorySearchBehaviour,
 ) -> State<'out, 'static, H> {
     State {
         out,
@@ -691,12 +732,14 @@ pub fn init_state<'out, H: Helper>(
         ctx: Context::new(history),
         hint: Some(Box::new("hint".to_owned())),
         highlight_char: false,
+        history_search_behaviour,
     }
 }
 
 #[cfg(test)]
 mod test {
     use super::init_state;
+    use crate::config::HistorySearchBehaviour;
     use crate::history::History;
     use crate::tty::Sink;
 
@@ -708,7 +751,8 @@ mod test {
         history.add("line1");
         let line = "current edited line";
         let helper: Option<()> = None;
-        let mut s = init_state(&mut out, line, 6, helper.as_ref(), &history);
+        let hsb = HistorySearchBehaviour::LineByLine;
+        let mut s = init_state(&mut out, line, 6, helper.as_ref(), &history, hsb);
         s.ctx.history_index = history.len();
 
         for _ in 0..2 {
@@ -738,4 +782,53 @@ mod test {
         assert_eq!(2, s.ctx.history_index);
         assert_eq!(line, s.line.as_str());
     }
+
+    #[test]
+    fn edit_history_prefix() {
+        let mut out = Sink::new();
+        let mut history = History::new();
+        history.add("foo");
+        history.add("bar");
+        history.add("cd abcdef");
+        history.add("ls");
+        history.add("cd abcdef");
+        history.add("ls");
+        history.add("cd ab123");
+        history.add("ls");
+        let line = "cd abxyz";
+        let helper: Option<()> = None;
+        let hsb = HistorySearchBehaviour::PrefixReverseSearch;
+        let mut s = init_state(&mut out, line, 5, helper.as_ref(), &history, hsb);
+        s.ctx.history_index = history.len();
+
+        s.edit_history_next(true).unwrap();
+        assert_eq!(line, s.saved_line_for_history.as_str());
+        assert_eq!(6, s.ctx.history_index);
+        assert_eq!("cd ab123", s.line.as_str());
+
+        s.edit_history_next(true).unwrap();
+        assert_eq!(line, s.saved_line_for_history.as_str());
+        assert_eq!(4, s.ctx.history_index);
+        assert_eq!("cd abcdef", s.line.as_str());
+
+        s.edit_history_next(true).unwrap();
+        assert_eq!(line, s.saved_line_for_history.as_str());
+        assert_eq!(0, s.ctx.history_index);
+        assert_eq!(line, s.line.as_str());
+
+        s.edit_history_next(false).unwrap();
+        assert_eq!(line, s.saved_line_for_history.as_str());
+        assert_eq!(2, s.ctx.history_index);
+        assert_eq!("cd abcdef", s.line.as_str());
+
+        s.edit_history_next(false).unwrap();
+        assert_eq!(line, s.saved_line_for_history.as_str());
+        assert_eq!(6, s.ctx.history_index);
+        assert_eq!("cd ab123", s.line.as_str());
+
+        s.edit_history_next(false).unwrap();
+        // assert_eq!(line, s.saved_line_for_history.as_str());
+        assert_eq!(8, s.ctx.history.len());
+        assert_eq!(line, s.line.as_str());
+    }
 }

src/lib.rs

@@ -451,7 +451,13 @@ fn readline_edit<H: Helper>(
 
     editor.reset_kill_ring(); // TODO recreate a new kill ring vs Arc<Mutex<KillRing>>
     let ctx = Context::new(&editor.history);
-    let mut s = State::new(&mut stdout, prompt, editor.helper.as_ref(), ctx);
+    let mut s = State::new(
+        &mut stdout,
+        prompt,
+        editor.helper.as_ref(),
+        ctx,
+        editor.config.history_search_behaviour(),
+    );
 
     let mut input_state = InputState::new(&editor.config, Arc::clone(&editor.custom_bindings));
 

src/test/mod.rs

@@ -4,7 +4,7 @@ use std::vec::IntoIter;
 use radix_trie::Trie;
 
 use crate::completion::Completer;
-use crate::config::{Config, EditMode};
+use crate::config::{Config, EditMode, HistorySearchBehaviour};
 use crate::edit::init_state;
 use crate::highlight::Highlighter;
 use crate::hint::Hinter;
@@ -57,7 +57,8 @@ fn complete_line() {
     let mut out = Sink::new();
     let history = crate::history::History::new();
     let helper = Some(SimpleCompleter);
-    let mut s = init_state(&mut out, "rus", 3, helper.as_ref(), &history);
+    let hsb = HistorySearchBehaviour::LineByLine;
+    let mut s = init_state(&mut out, "rus", 3, helper.as_ref(), &history, hsb);
     let config = Config::default();
     let mut input_state = InputState::new(&config, Arc::new(RwLock::new(Trie::new())));
     let keys = vec![E::ENTER];