Custom validator and prompt code examples (#500)

* custom validator and prompt

* Split prompt and validator demo into two files

Also add info text when running

Co-authored-by: sholderbach <sholderbach@users.noreply.github.com>

examples/custom_prompt.rs

@@ -0,0 +1,75 @@
+// Create a reedline object with a custom prompt.
+// cargo run --example custom_prompt
+//
+// Pressing keys will increase the right prompt value
+
+use reedline::{
+    Prompt, PromptEditMode, PromptHistorySearch, PromptHistorySearchStatus, Reedline, Signal,
+};
+use std::{borrow::Cow, cell::Cell, io};
+
+// For custom prompt, implement the Prompt trait
+//
+// This example displays the number of keystrokes
+// or rather increments each time the prompt is rendered.
+#[derive(Clone)]
+pub struct CustomPrompt(Cell<u32>, &'static str);
+pub static DEFAULT_MULTILINE_INDICATOR: &str = "::: ";
+impl Prompt for CustomPrompt {
+    fn render_prompt_left(&self) -> Cow<str> {
+        {
+            Cow::Owned(self.1.to_string())
+        }
+    }
+
+    fn render_prompt_right(&self) -> Cow<str> {
+        {
+            let old = self.0.get();
+            self.0.set(old + 1);
+            Cow::Owned(format!("[{}]", old))
+        }
+    }
+
+    fn render_prompt_indicator(&self, _edit_mode: PromptEditMode) -> Cow<str> {
+        Cow::Owned(">".to_string())
+    }
+
+    fn render_prompt_multiline_indicator(&self) -> Cow<str> {
+        Cow::Borrowed(DEFAULT_MULTILINE_INDICATOR)
+    }
+
+    fn render_prompt_history_search_indicator(
+        &self,
+        history_search: PromptHistorySearch,
+    ) -> Cow<str> {
+        let prefix = match history_search.status {
+            PromptHistorySearchStatus::Passing => "",
+            PromptHistorySearchStatus::Failing => "failing ",
+        };
+
+        Cow::Owned(format!(
+            "({}reverse-search: {}) ",
+            prefix, history_search.term
+        ))
+    }
+}
+
+fn main() -> io::Result<()> {
+    println!("Custom prompt demo:\nAbort with Ctrl-C or Ctrl-D");
+    let mut line_editor = Reedline::create();
+
+    let prompt = CustomPrompt(Cell::new(0), "Custom Prompt");
+
+    loop {
+        let sig = line_editor.read_line(&prompt)?;
+        match sig {
+            Signal::Success(buffer) => {
+                println!("We processed: {}", buffer);
+            }
+            Signal::CtrlD | Signal::CtrlC => {
+                println!("\nAborted!");
+                break Ok(());
+            }
+        }
+    }
+}

examples/validator.rs

@@ -0,0 +1,41 @@
+// Create a reedline object with a custom validator to break the line on unfinished input.
+// cargo run --example validator
+//
+// Input "complete" followed by [Enter], will accept the input line (Signal::Succeed will be called)
+// Pressing [Enter] will in other cases give you a multi-line prompt.
+
+use reedline::{DefaultPrompt, Reedline, Signal, ValidationResult, Validator};
+use std::io;
+
+struct CustomValidator;
+
+// For custom validation, implement the Validator trait
+impl Validator for CustomValidator {
+    fn validate(&self, line: &str) -> ValidationResult {
+        if line == "complete" {
+            ValidationResult::Complete
+        } else {
+            ValidationResult::Incomplete
+        }
+    }
+}
+
+fn main() -> io::Result<()> {
+    println!("Input \"complete\" followed by [Enter], will accept the input line (Signal::Succeed will be called)\nPressing [Enter] will in other cases give you a multi-line prompt.\nAbort with Ctrl-C or Ctrl-D");
+    let mut line_editor = Reedline::create().with_validator(Box::new(CustomValidator));
+
+    let prompt = DefaultPrompt::default();
+
+    loop {
+        let sig = line_editor.read_line(&prompt)?;
+        match sig {
+            Signal::Success(buffer) => {
+                println!("We processed: {}", buffer);
+            }
+            Signal::CtrlD | Signal::CtrlC => {
+                println!("\nAborted!");
+                break Ok(());
+            }
+        }
+    }
+}