rustyline/
hint.rs

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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
43/// Add suggestion based on previous history entries matching current user
44/// input.
45#[derive(Default)]
46pub struct HistoryHinter {}
47
48impl HistoryHinter {
49    /// Create a new `HistoryHinter`
50    pub fn new() -> Self {
51        Self::default()
52    }
53}
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            .unwrap_or(None)
71        {
72            if sr.entry == line {
73                return None;
74            }
75            return Some(sr.entry[pos..].to_owned());
76        }
77        None
78    }
79}
80
81#[cfg(test)]
82mod test {
83    use super::{Hinter, HistoryHinter};
84    use crate::history::DefaultHistory;
85    use crate::Context;
86
87    #[test]
88    pub fn empty_history() {
89        let history = DefaultHistory::new();
90        let ctx = Context::new(&history);
91        let hinter = HistoryHinter {};
92        let hint = hinter.hint("test", 4, &ctx);
93        assert_eq!(None, hint);
94    }
95}
rustyline/hint.rs

rustyline/
hint.rs
