Lift line editor construction out of loop (#5041)

Enables the use of some features on reedline

- Keeping the line when clearing the screen with `Ctrl-L`
- Using the internal cut buffer between lines
- Submitting external commands via keybinding and keeping the line

Additional effect:

Keep the history around and do basic syncs (performance improvement
minimal as session changes have to be read and written)

Additional change:

Give the option to defer writing/rereading the history file to the
closing of the session ($config.sync_history_on_enter)

Cargo.lock

@@ -3428,7 +3428,7 @@ dependencies = [
 [[package]]
 name = "reedline"
 version = "0.3.1"
-source = "git+https://github.com/nushell/reedline?branch=main#bc18ba3260604172700bf5996f66635ee428d625"
+source = "git+https://github.com/nushell/reedline?branch=main#0f92985c69efca2567ad40ebc0381864e91aff8c"
 dependencies = [
  "chrono",
  "crossterm",

crates/nu-cli/src/repl.rs

@@ -104,6 +104,45 @@ pub fn evaluate_repl(
         },
     );
 
+    if is_perf_true {
+        info!(
+            "load config initially {}:{}:{}",
+            file!(),
+            line!(),
+            column!()
+        );
+    }
+
+    // Get the config once for the history `max_history_size`
+    // Updating that will not be possible in one session
+    let mut config = match stack.get_config() {
+        Ok(config) => config,
+        Err(e) => {
+            let working_set = StateWorkingSet::new(engine_state);
+
+            report_error(&working_set, &e);
+            Config::default()
+        }
+    };
+
+    if is_perf_true {
+        info!("setup reedline {}:{}:{}", file!(), line!(), column!());
+    }
+    let mut line_editor = Reedline::create().into_diagnostic()?;
+    if let Some(history_path) = history_path.as_deref() {
+        if is_perf_true {
+            info!("setup history {}:{}:{}", file!(), line!(), column!());
+        }
+        let history = Box::new(
+            FileBackedHistory::with_file(
+                config.max_history_size as usize,
+                history_path.to_path_buf(),
+            )
+            .into_diagnostic()?,
+        );
+        line_editor = line_editor.with_history(history).into_diagnostic()?;
+    };
+
     loop {
         if is_perf_true {
             info!(
@@ -114,7 +153,7 @@ pub fn evaluate_repl(
             );
         }
 
-        let config = match stack.get_config() {
+        config = match stack.get_config() {
             Ok(config) => config,
             Err(e) => {
                 let working_set = StateWorkingSet::new(engine_state);
@@ -123,18 +162,14 @@ pub fn evaluate_repl(
                 Config::default()
             }
         };
+        let color_hm = get_color_config(&config);
 
         //Reset the ctrl-c handler
         if let Some(ctrlc) = &mut engine_state.ctrlc {
             ctrlc.store(false, Ordering::SeqCst);
         }
 
-        if is_perf_true {
-            info!("setup line editor {}:{}:{}", file!(), line!(), column!());
-        }
-
-        let mut line_editor = Reedline::create()
-            .into_diagnostic()?
+        line_editor = line_editor
             .with_highlighter(Box::new(NuHighlighter {
                 engine_state: engine_state.clone(),
                 config: config.clone(),
@@ -143,6 +178,9 @@ pub fn evaluate_repl(
             .with_validator(Box::new(NuValidator {
                 engine_state: engine_state.clone(),
             }))
+            .with_hinter(Box::new(
+                DefaultHinter::default().with_style(color_hm["hints"]),
+            ))
             .with_completer(Box::new(NuCompleter::new(
                 engine_state.clone(),
                 stack.clone(),
@@ -153,7 +191,7 @@ pub fn evaluate_repl(
             .with_ansi_colors(config.use_ansi_coloring);
 
         if is_perf_true {
-            info!("setup reedline {}:{}:{}", file!(), line!(), column!());
+            info!("update reedline {}:{}:{}", file!(), line!(), column!());
         }
 
         line_editor = add_completion_menu(line_editor, &config);
@@ -168,38 +206,12 @@ pub fn evaluate_repl(
         //FIXME: if config.use_ansi_coloring is false then we should
         // turn off the hinter but I don't see any way to do that yet.
 
-        let color_hm = get_color_config(&config);
-
+        if config.sync_history_on_enter {
             if is_perf_true {
-            info!(
-                "setup history and hinter {}:{}:{}",
-                file!(),
-                line!(),
-                column!()
-            );
+                info!("sync history {}:{}:{}", file!(), line!(), column!());
             }
-
-        line_editor = if let Some(history_path) = history_path.clone() {
-            let history = std::fs::read_to_string(&history_path);
-            if history.is_ok() {
-                line_editor
-                    .with_hinter(Box::new(
-                        DefaultHinter::default().with_style(color_hm["hints"]),
-                    ))
-                    .with_history(Box::new(
-                        FileBackedHistory::with_file(
-                            config.max_history_size as usize,
-                            history_path.clone(),
-                        )
-                        .into_diagnostic()?,
-                    ))
-                    .into_diagnostic()?
-            } else {
-                line_editor
+            line_editor.sync_history().into_diagnostic()?;
         }
-        } else {
-            line_editor
-        };
 
         if is_perf_true {
             info!("setup keybindings {}:{}:{}", file!(), line!(), column!());

crates/nu-protocol/src/config.rs

@@ -29,6 +29,7 @@ pub struct Config {
     pub partial_completions: bool,
     pub edit_mode: String,
     pub max_history_size: i64,
+    pub sync_history_on_enter: bool,
     pub log_level: String,
     pub menu_config: HashMap<String, Value>,
     pub keybindings: Vec<ParsedKeybinding>,
@@ -54,6 +55,7 @@ impl Default for Config {
             partial_completions: true,
             edit_mode: "emacs".into(),
             max_history_size: 1000,
+            sync_history_on_enter: true,
             log_level: String::new(),
             menu_config: HashMap::new(),
             history_config: HashMap::new(),
@@ -199,6 +201,13 @@ impl Value {
                             eprintln!("$config.max_history_size is not an integer")
                         }
                     }
+                    "sync_history_on_enter" => {
+                        if let Ok(b) = value.as_bool() {
+                            config.sync_history_on_enter = b;
+                        } else {
+                            eprintln!("$config.sync_history_on_enter is not a bool")
+                        }
+                    }
                     "log_level" => {
                         if let Ok(v) = value.as_string() {
                             config.log_level = v.to_lowercase();

docs/sample_config/default_config.nu

@@ -196,7 +196,8 @@ let $config = {
   use_ansi_coloring: true
   filesize_format: "auto" # b, kb, kib, mb, mib, gb, gib, tb, tib, pb, pib, eb, eib, zb, zib, auto
   edit_mode: emacs # emacs, vi
-  max_history_size: 10000
+  max_history_size: 10000 # Session has to be reloaded for this to take effect
+  sync_history_on_enter: true # Enable to share the history between multiple sessions, else you have to close the session to persist history to file
   menu_config: {
     columns: 4
     col_width: 20   # Optional value. If missing all the screen width is used to calculate column width