Add internal clear command (#1249)

* Add clear.rs

* update

* update

* cross-platformify

* update

* fix

* format

* fix warnings

* update implementation

* remove return

* remove semicolon

* change from `.output()` to `.status()`

* format

src/cli.rs

@@ -226,6 +226,7 @@ impl History {
     }
 }
 
+#[allow(dead_code)]
 fn create_default_starship_config() -> Option<toml::Value> {
     let mut map = toml::value::Table::new();
     map.insert("add_newline".into(), toml::Value::Boolean(false));
@@ -265,6 +266,7 @@ pub async fn cli() -> Result<(), Box<dyn Error>> {
             per_item_command(Mkdir),
             per_item_command(Move),
             whole_stream_command(Version),
+            whole_stream_command(Clear),
             whole_stream_command(What),
             whole_stream_command(Which),
             whole_stream_command(Debug),

src/commands.rs

@@ -115,6 +115,8 @@ pub(crate) use debug::Debug;
 pub(crate) use default::Default;
 pub(crate) use echo::Echo;
 pub(crate) use edit::Edit;
+pub(crate) mod clear;
+pub(crate) use clear::Clear;
 pub(crate) use enter::Enter;
 pub(crate) use env::Env;
 #[allow(unused_imports)]

src/commands/clear.rs

@@ -0,0 +1,40 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::Signature;
+use std::process::Command;
+
+pub struct Clear;
+
+impl WholeStreamCommand for Clear {
+    fn name(&self) -> &str {
+        "clear"
+    }
+    fn signature(&self) -> Signature {
+        Signature::build("clear")
+    }
+    fn usage(&self) -> &str {
+        "clears the terminal"
+    }
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        clear(args, registry)
+    }
+}
+fn clear(_args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    if cfg!(windows) {
+        Command::new("cmd")
+            .args(&["/C", "cls"])
+            .status()
+            .expect("failed to execute process");
+    } else if cfg!(unix) {
+        Command::new("/bin/sh")
+            .args(&["-c", "clear"])
+            .status()
+            .expect("failed to execute process");
+    }
+    Ok(OutputStream::empty())
+}