WIP: Introduce Prompt trait

For line continuations.
And Vi input mode indicator.

src/edit.rs

@@ -14,15 +14,16 @@ use crate::keymap::{Anchor, At, CharSearch, Cmd, Movement, RepeatCount, Word};
 use crate::keymap::{InputState, Invoke, Refresher};
 use crate::layout::{Layout, Position};
 use crate::line_buffer::{LineBuffer, WordAction, MAX_LINE};
+use crate::prompt::Prompt;
 use crate::tty::{Renderer, Term, Terminal};
 use crate::undo::Changeset;
 use crate::validate::{ValidationContext, ValidationResult};
 
 /// Represent the state during line editing.
 /// Implement rendering.
-pub struct State<'out, 'prompt, H: Helper> {
+pub struct State<'out, 'prompt, H: Helper, P: Prompt + ?Sized> {
     pub out: &'out mut <Terminal as Term>::Writer,
-    prompt: &'prompt str,  // Prompt to display (rl_prompt)
+    prompt: &'prompt P,    // Prompt to display (rl_prompt)
     prompt_size: Position, // Prompt Unicode/visible width and height
     pub line: LineBuffer,  // Edited line buffer
     pub layout: Layout,
@@ -41,13 +42,13 @@ enum Info<'m> {
     Msg(Option<&'m str>),
 }
 
-impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
+impl<'out, 'prompt, H: Helper, P: Prompt + ?Sized> State<'out, 'prompt, H, P> {
     pub fn new(
         out: &'out mut <Terminal as Term>::Writer,
-        prompt: &'prompt str,
+        prompt: &'prompt P,
         helper: Option<&'out H>,
         ctx: Context<'out>,
-    ) -> State<'out, 'prompt, H> {
+    ) -> State<'out, 'prompt, H, P> {
         let prompt_size = out.calculate_position(prompt, Position::default());
         State {
             out,
@@ -135,7 +136,7 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
 
     fn refresh(
         &mut self,
-        prompt: &str,
+        prompt: &P,
         prompt_size: Position,
         default_prompt: bool,
         info: Info<'_>,
@@ -231,13 +232,13 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
     }
 }
 
-impl<'out, 'prompt, H: Helper> Invoke for State<'out, 'prompt, H> {
+impl<'out, 'prompt, H: Helper, P: Prompt + ?Sized> Invoke for State<'out, 'prompt, H, P> {
     fn input(&self) -> &str {
         self.line.as_str()
     }
 }
 
-impl<'out, 'prompt, H: Helper> Refresher for State<'out, 'prompt, H> {
+impl<'out, 'prompt, H: Helper, P: Prompt + ?Sized> Refresher for State<'out, 'prompt, H, P> {
     fn refresh_line(&mut self) -> Result<()> {
         let prompt_size = self.prompt_size;
         self.hint();
@@ -280,10 +281,10 @@ impl<'out, 'prompt, H: Helper> Refresher for State<'out, 'prompt, H> {
     }
 }
 
-impl<'out, 'prompt, H: Helper> fmt::Debug for State<'out, 'prompt, H> {
+impl<'out, 'prompt, H: Helper, P: Prompt + ?Sized> fmt::Debug for State<'out, 'prompt, H, P> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("State")
-            .field("prompt", &self.prompt)
+            .field("prompt", &self.prompt.get_prompt(&()))
             .field("prompt_size", &self.prompt_size)
             .field("buf", &self.line)
             .field("cols", &self.out.get_columns())
@@ -293,7 +294,7 @@ impl<'out, 'prompt, H: Helper> fmt::Debug for State<'out, 'prompt, H> {
     }
 }
 
-impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
+impl<'out, 'prompt, H: Helper, P: Prompt + ?Sized> State<'out, 'prompt, H, P> {
     pub fn clear_screen(&mut self) -> Result<()> {
         self.out.clear_screen()?;
         self.layout.cursor = Position::default();
@@ -661,7 +662,7 @@ pub fn init_state<'out, H: Helper>(
     pos: usize,
     helper: Option<&'out H>,
     history: &'out crate::history::History,
-) -> State<'out, 'static, H> {
+) -> State<'out, 'static, H, str> {
     State {
         out,
         prompt: "",

src/lib.rs

@@ -29,6 +29,7 @@ mod keys;
 mod kill_ring;
 mod layout;
 pub mod line_buffer;
+pub mod prompt;
 mod tty;
 mod undo;
 pub mod validate;
@@ -58,15 +59,16 @@ use crate::keymap::{InputState, Refresher};
 pub use crate::keys::KeyPress;
 use crate::kill_ring::{KillRing, Mode};
 use crate::line_buffer::WordAction;
+pub use crate::prompt::Prompt;
 use crate::validate::Validator;
 
 /// The error type for I/O and Linux Syscalls (Errno)
 pub type Result<T> = result::Result<T, error::ReadlineError>;
 
 /// Completes the line/word
-fn complete_line<H: Helper>(
+fn complete_line<H: Helper, P: Prompt + ?Sized>(
     rdr: &mut <Terminal as Term>::Reader,
-    s: &mut State<'_, '_, H>,
+    s: &mut State<'_, '_, H, P>,
     input_state: &mut InputState,
     config: &Config,
 ) -> Result<Option<Cmd>> {
@@ -231,7 +233,7 @@ fn complete_line<H: Helper>(
 }
 
 /// Completes the current hint
-fn complete_hint_line<H: Helper>(s: &mut State<'_, '_, H>) -> Result<()> {
+fn complete_hint_line<H: Helper, P: Prompt + ?Sized>(s: &mut State<'_, '_, H, P>) -> Result<()> {
     let hint = match s.hint.as_ref() {
         Some(hint) => hint,
         None => return Ok(()),
@@ -244,9 +246,9 @@ fn complete_hint_line<H: Helper>(s: &mut State<'_, '_, H>) -> Result<()> {
     Ok(())
 }
 
-fn page_completions<C: Candidate, H: Helper>(
+fn page_completions<C: Candidate, H: Helper, P: Prompt + ?Sized>(
     rdr: &mut <Terminal as Term>::Reader,
-    s: &mut State<'_, '_, H>,
+    s: &mut State<'_, '_, H, P>,
     input_state: &mut InputState,
     candidates: &[C],
 ) -> Result<Option<Cmd>> {
@@ -324,9 +326,9 @@ fn page_completions<C: Candidate, H: Helper>(
 }
 
 /// Incremental search
-fn reverse_incremental_search<H: Helper>(
+fn reverse_incremental_search<H: Helper, P: Prompt + ?Sized>(
     rdr: &mut <Terminal as Term>::Reader,
-    s: &mut State<'_, '_, H>,
+    s: &mut State<'_, '_, H, P>,
     input_state: &mut InputState,
     history: &History,
 ) -> Result<Option<Cmd>> {
@@ -412,8 +414,8 @@ fn reverse_incremental_search<H: Helper>(
 /// Handles reading and editing the readline buffer.
 /// It will also handle special inputs in an appropriate fashion
 /// (e.g., C-c will exit readline)
-fn readline_edit<H: Helper>(
-    prompt: &str,
+fn readline_edit<H: Helper, P: Prompt + ?Sized>(
+    prompt: &P,
     initial: Option<(&str, &str)>,
     editor: &mut Editor<H>,
     original_mode: &tty::Mode,
@@ -687,8 +689,8 @@ impl Drop for Guard<'_> {
 
 /// Readline method that will enable RAW mode, call the `readline_edit()`
 /// method and disable raw mode
-fn readline_raw<H: Helper>(
-    prompt: &str,
+fn readline_raw<H: Helper, P: Prompt + ?Sized>(
+    prompt: &P,
     initial: Option<(&str, &str)>,
     editor: &mut Editor<H>,
 ) -> Result<String> {
@@ -798,7 +800,7 @@ impl<H: Helper> Editor<H> {
     /// terminal.
     /// Otherwise (e.g., if `stdin` is a pipe or the terminal is not supported),
     /// it uses file-style interaction.
-    pub fn readline(&mut self, prompt: &str) -> Result<String> {
+    pub fn readline<P: Prompt + ?Sized>(&mut self, prompt: &P) -> Result<String> {
         self.readline_with(prompt, None)
     }
 
@@ -813,12 +815,16 @@ impl<H: Helper> Editor<H> {
         self.readline_with(prompt, Some(initial))
     }
 
-    fn readline_with(&mut self, prompt: &str, initial: Option<(&str, &str)>) -> Result<String> {
+    fn readline_with<P: Prompt + ?Sized>(
+        &mut self,
+        prompt: &P,
+        initial: Option<(&str, &str)>,
+    ) -> Result<String> {
         if self.term.is_unsupported() {
             debug!(target: "rustyline", "unsupported terminal");
             // Write prompt and flush it to stdout
             let mut stdout = io::stdout();
-            stdout.write_all(prompt.as_bytes())?;
+            stdout.write_all(prompt.get_prompt(&()).as_bytes())?;
             stdout.flush()?;
 
             readline_direct()

src/prompt.rs

@@ -0,0 +1,46 @@
+//! Prompt and line continuations
+use std::borrow::Cow::{self, Borrowed};
+
+/// Prompt and line continuations
+pub trait Prompt {
+    /// Returns text to be shown as the prompt at the first line.
+    /// Or text for the next lines of the input when
+    /// `Prompt::has_continuation()`.
+    fn get_prompt<'p>(&'p self, ctx: &dyn PromptContext) -> Cow<'p, str>;
+    /// Returns `true` when line continuations should be displayed. `false` by
+    /// default.
+    fn has_continuation(&self) -> bool {
+        false
+    }
+}
+
+/*
+We can cache Prompt::get_prompt result(s) if:
+ * if `input_mode` is kept untouched
+ * or (if `Prompt::has_continuation`), if `wrap_count`/`line_number` are kept untouched
+
+TODO
+* Layout impacts
+ - compute_layout
+ - State.prompt_size
+ - ...
+* Highlight impacts
+ - highlight_prompt
+ */
+
+impl PromptContext for () {}
+
+pub trait PromptContext {
+    // Current line number. Computed/meaningful only when
+    // `Prompt::has_continuation()`. fn line_number(&self) -> usize;
+    // Soft wrap count. Computed/meaningful only when `Prompt::has_continuation()`.
+    //fn wrap_count(&self) -> usize;
+    // Vi input mode. `None` with default emacs editing mode.
+    //fn input_mode(&self) -> Option<InputMode>;
+}
+
+impl Prompt for str {
+    fn get_prompt<'p>(&'p self, _: &dyn PromptContext) -> Cow<'p, str> {
+        Borrowed(self)
+    }
+}