rustyline/
hint.rs

1//! Hints (suggestions at the right of the prompt as you type).
2
3use crate::history::SearchDirection;
4use crate::Context;
5
6/// A hint returned by Hinter
7pub trait Hint {
8    /// Text to display when hint is active
9    fn display(&self) -> &str;
10    /// Text to insert in line when right arrow is pressed
11    fn completion(&self) -> Option<&str>;
12}
13
14impl Hint for String {
15    fn display(&self) -> &str {
16        self.as_str()
17    }
18
19    fn completion(&self) -> Option<&str> {
20        Some(self.as_str())
21    }
22}
23
24/// Hints provider
25pub trait Hinter {
26    /// Specific hint type
27    type Hint: Hint + 'static;
28
29    /// Takes the currently edited `line` with the cursor `pos`ition and
30    /// returns the string that should be displayed or `None`
31    /// if no hint is available for the text the user currently typed.
32    // TODO Validate: called while editing line but not while moving cursor.
33    fn hint(&self, line: &str, pos: usize, ctx: &Context<'_>) -> Option<Self::Hint> {
34        let _ = (line, pos, ctx);
35        None
36    }
37}
38
39impl Hinter for () {
40    type Hint = String;
41}
42
43impl<'r, H: ?Sized + Hinter> Hinter for &'r H {
44    type Hint = H::Hint;
45
46    fn hint(&self, line: &str, pos: usize, ctx: &Context<'_>) -> Option<Self::Hint> {
47        (**self).hint(line, pos, ctx)
48    }
49}
50
51/// Add suggestion based on previous history entries matching current user
52/// input.
53pub struct HistoryHinter {}
54
55impl Hinter for HistoryHinter {
56    type Hint = String;
57
58    fn hint(&self, line: &str, pos: usize, ctx: &Context<'_>) -> Option<String> {
59        if line.is_empty() || pos < line.len() {
60            return None;
61        }
62        let start = if ctx.history_index() == ctx.history().len() {
63            ctx.history_index().saturating_sub(1)
64        } else {
65            ctx.history_index()
66        };
67        if let Some(sr) = ctx
68            .history
69            .starts_with(line, start, SearchDirection::Reverse)
70        {
71            if sr.entry == line {
72                return None;
73            }
74            return Some(sr.entry[pos..].to_owned());
75        }
76        None
77    }
78}
79
80#[cfg(test)]
81mod test {
82    use super::{Hinter, HistoryHinter};
83    use crate::history::History;
84    use crate::Context;
85
86    #[test]
87    pub fn empty_history() {
88        let history = History::new();
89        let ctx = Context::new(&history);
90        let hinter = HistoryHinter {};
91        let hint = hinter.hint("test", 4, &ctx);
92        assert_eq!(None, hint);
93    }
94}
rustyline/hint.rs

rustyline/
hint.rs
