add command g to switch shell quickly (#4014)

Signed-off-by: Tw <tw19881113@gmail.com>

crates/nu-command/src/commands/shells/goto.rs

@@ -0,0 +1,51 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{CommandAction, ReturnSuccess, Signature, SyntaxShape};
+
+pub struct Goto;
+
+impl WholeStreamCommand for Goto {
+    fn name(&self) -> &str {
+        "g"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("g").required("index", SyntaxShape::Int, "the shell's index to go to")
+    }
+
+    fn usage(&self) -> &str {
+        "Go to specified shell."
+    }
+
+    fn run_with_actions(&self, args: CommandArgs) -> Result<ActionStream, ShellError> {
+        goto(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Enter the first shell",
+            example: "g 0",
+            result: None,
+        }]
+    }
+}
+
+fn goto(args: CommandArgs) -> Result<ActionStream, ShellError> {
+    Ok(ActionStream::one(ReturnSuccess::action(
+        CommandAction::GotoShell(args.req(0)?),
+    )))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Goto;
+    use super::ShellError;
+
+    #[test]
+    fn examples_work_as_expected() -> Result<(), ShellError> {
+        use crate::examples::test as test_examples;
+
+        test_examples(Goto {})
+    }
+}

crates/nu-command/src/commands/shells/mod.rs

@@ -1,11 +1,13 @@
 mod command;
 mod enter;
 mod exit;
+mod goto;
 mod next;
 mod prev;
 
 pub use command::Shells;
 pub use enter::Enter;
 pub use exit::Exit;
+pub use goto::Goto;
 pub use next::Next;
 pub use prev::Previous;

crates/nu-command/src/default_context.rs

@@ -77,6 +77,7 @@ pub fn create_default_context(interactive: bool) -> Result<EvaluationContext, Bo
             // Shells
             whole_stream_command(Next),
             whole_stream_command(Previous),
+            whole_stream_command(Goto),
             whole_stream_command(Shells),
             whole_stream_command(Enter),
             whole_stream_command(Exit),

crates/nu-engine/src/evaluate/internal.rs

@@ -177,6 +177,9 @@ impl Iterator for InternalIterator {
                     CommandAction::NextShell => {
                         self.context.shell_manager().next();
                     }
+                    CommandAction::GotoShell(i) => {
+                        self.context.shell_manager().goto(i);
+                    }
                     CommandAction::LeaveShell(code) => {
                         self.context.shell_manager().remove_at_current();
                         if self.context.shell_manager().is_empty() {

crates/nu-engine/src/shell/shell_manager.rs

@@ -136,6 +136,16 @@ impl ShellManager {
         self.set_path(self.path())
     }
 
+    pub fn goto(&self, i: usize) {
+        {
+            let shell_len = self.shells.lock().len();
+            if i < shell_len {
+                self.current_shell.store(i, Ordering::SeqCst);
+            }
+        }
+        self.set_path(self.path())
+    }
+
     pub fn homedir(&self) -> Option<PathBuf> {
         let env = self.shells.lock();
 

crates/nu-protocol/src/return_value.rs

@@ -28,6 +28,8 @@ pub enum CommandAction {
     PreviousShell,
     /// Go to the next shell in the shell ring buffer
     NextShell,
+    /// Jump to the specified shell in the shell ring buffer
+    GotoShell(usize),
     /// Leave the current shell. If it's the last shell, exit out of Nu
     LeaveShell(i32),
 }
@@ -51,6 +53,7 @@ impl PrettyDebug for CommandAction {
             CommandAction::AddPlugins(..) => DbgDocBldr::description("add plugins"),
             CommandAction::PreviousShell => DbgDocBldr::description("previous shell"),
             CommandAction::NextShell => DbgDocBldr::description("next shell"),
+            CommandAction::GotoShell(_) => DbgDocBldr::description("goto shell"),
             CommandAction::LeaveShell(_) => DbgDocBldr::description("leave shell"),
             CommandAction::UnloadConfig(cfg) => {
                 DbgDocBldr::description(format!("unload config {:?}", cfg))