Add History Search Behaviour

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::{OutputStreamType, HistorySearchBehaviour};
 use rustyline::error::ReadlineError;
 use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
 use rustyline::hint::{Hinter, HistoryHinter};
@@ -85,6 +85,7 @@ fn main() -> rustyline::Result<()> {
         .completion_type(CompletionType::List)
         .edit_mode(EditMode::Emacs)
         .output_stream(OutputStreamType::Stdout)
+        .history_search_behaviour(HistorySearchBehaviour::HistoryLineByLine)
         .build();
     let h = MyHelper {
         completer: FilenameCompleter::new(),

src/config.rs

@@ -28,6 +28,9 @@ pub struct Config {
     output_stream: OutputStreamType,
     /// Horizontal space taken by a tab.
     tab_stop: usize,
+    /// 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 {
@@ -145,6 +148,18 @@ impl Config {
     pub(crate) fn set_tab_stop(&mut self, tab_stop: usize) {
         self.tab_stop = tab_stop;
     }
+
+    /// 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 {
@@ -162,6 +177,7 @@ impl Default for Config {
             color_mode: ColorMode::Enabled,
             output_stream: OutputStreamType::Stdout,
             tab_stop: 8,
+            history_search_behaviour: HistorySearchBehaviour::HistoryLineByLine,
         }
     }
 }
@@ -252,6 +268,17 @@ 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.
+    HistoryLineByLine,
+    /// Implicit reverse search: Only show history entries which start with the current prefix
+    /// before the cursor.
+    ReverseSearchPrefix,
+}
+
 /// Configuration builder
 #[derive(Clone, Debug, Default)]
 pub struct Builder {
@@ -357,6 +384,15 @@ 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
@@ -451,4 +487,12 @@ pub trait Configurer {
     fn set_tab_stop(&mut self, tab_stop: usize) {
         self.config_mut().set_tab_stop(tab_stop);
     }
+
+    /// 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::history::Direction;
 use crate::keymap::{Anchor, At, CharSearch, Cmd, Movement, RepeatCount, Word};
@@ -33,6 +34,7 @@ pub struct State<'out, 'prompt, H: Helper> {
     pub ctx: Context<'out>,   // Give access to history for `hinter`
     pub hint: Option<String>, // 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> {
@@ -47,6 +49,7 @@ 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 {
@@ -62,6 +65,7 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
             ctx,
             hint: None,
             highlight_char: false,
+            history_search_behaviour,
         }
     }
 
@@ -229,6 +233,12 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
             Ok(true)
         }
     }
+
+    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> {
@@ -574,25 +584,42 @@ 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::ReverseSearchPrefix 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::HistoryLineByLine | HistorySearchBehaviour::ReverseSearchPrefix => {
+                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::HistoryLineByLine => buf.len(),
+                        HistorySearchBehaviour::ReverseSearchPrefix => 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();
@@ -614,13 +641,17 @@ 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()
+            let pos = if keep_cursor_pos {
+                self.line.pos()
+            } else {
+                buf.len()
+            };
+            self.update_line(buf, pos);
         } else {
-            self.out.beep()
+            self.restore();
+            self.out.beep()?;
         }
+        self.refresh_line()
     }
 
     /// Substitute the currently edited line with the first/last history entry.
@@ -642,9 +673,7 @@ 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

src/lib.rs

@@ -426,7 +426,7 @@ 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, helper, ctx);
+    let mut s = State::new(&mut stdout, prompt, helper, ctx, editor.config.history_search_behaviour());
     let mut input_state = InputState::new(&editor.config, Arc::clone(&editor.custom_bindings));
 
     s.line.set_delete_listener(editor.kill_ring.clone());
@@ -555,8 +555,8 @@ fn readline_edit<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()?