feat(builtins): add exit builtin

Signed-off-by: Charlotte Meyer <dev@buffet.sh>

crates/oyster/src/main.rs

@@ -9,13 +9,8 @@ fn main() {
     shell.builtins_mut().add_defaults();
     let mut exit_code = Status::SUCCESS;
 
-    loop {
+    while shell.is_running() {
         let prog = readline("> ").unwrap();
-
-        if prog.trim() == "exit" {
-            break;
-        }
-
         let ast = Code::try_from(prog.as_ref()).unwrap();
         exit_code = shell.run(&ast).unwrap();
     }

crates/oyster_runtime/src/builtins/mod.rs

@@ -12,6 +12,11 @@ pub struct Builtin {
     pub fun: fn(shell: &mut Shell, args: &[Cow<OsStr>]),
 }
 
+#[builtin(description = "exit the shell", nofork)]
+pub fn exit(shell: &mut Shell, _args: &[Cow<OsStr>]) {
+    shell.is_running = false;
+}
+
 #[builtin(description = "prints help for different builtins")]
 pub fn help(shell: &mut Shell, _args: &[Cow<OsStr>]) {
     println!(
@@ -48,6 +53,7 @@ impl BuiltinMap {
 
     /// Add default builtins.
     pub fn add_defaults(&mut self) {
+        self.add(exit);
         self.add(help);
     }
 }

crates/oyster_runtime/src/lib.rs

@@ -66,6 +66,7 @@ pub enum RuntimeError {
 }
 
 pub struct Shell {
+    is_running: bool,
     builtins: BuiltinMap,
 }
 
@@ -79,10 +80,15 @@ impl Shell {
         }
 
         Ok(Shell {
+            is_running: true,
             builtins: Default::default(),
         })
     }
 
+    pub fn is_running(&self) -> bool {
+        self.is_running
+    }
+
     pub fn run<'a>(&mut self, code: &'a ast::Code) -> Result<Status, RuntimeError> {
         let mut last_status = Status::SUCCESS;