feat(builtins): add nofork on builtins

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

crates/oyster_builtin_proc/src/lib.rs

@@ -9,6 +9,8 @@ use syn::{parse_macro_input, AttributeArgs, Ident, ItemFn, Signature};
 struct AttrArgs {
     #[darling(default)]
     description: String,
+    #[darling(default)]
+    nofork: bool,
 }
 
 #[proc_macro_attribute]
@@ -25,7 +27,10 @@ pub fn builtin(attr: TokenStream, item: TokenStream) -> TokenStream {
     } = sig;
 
     let name = ident.to_string();
-    let AttrArgs { description } = match AttrArgs::from_list(&attrs) {
+    let AttrArgs {
+        description,
+        nofork,
+    } = match AttrArgs::from_list(&attrs) {
         Ok(args) => args,
         Err(err) => return err.write_errors().into(),
     };
@@ -46,6 +51,7 @@ pub fn builtin(attr: TokenStream, item: TokenStream) -> TokenStream {
             #builtin {
                 name: #name,
                 description: #description,
+                nofork: #nofork,
                 fun: #ident,
             }
         };

crates/oyster_runtime/src/builtins/mod.rs

@@ -8,6 +8,7 @@ use crate::Shell;
 pub struct Builtin {
     pub name: &'static str,
     pub description: &'static str,
+    pub nofork: bool,
     pub fun: fn(shell: &mut Shell, args: &[Cow<OsStr>]),
 }
 

crates/oyster_runtime/src/pipeline.rs

@@ -104,7 +104,7 @@ impl<'a> PreparedCommand<'a> {
             }
         };
 
-        let child = match self.kind {
+        match self.kind {
             CommandKind::External => {
                 let mut cmd = Command::new(&self.cmd);
                 cmd.args(self.args);
@@ -131,38 +131,54 @@ impl<'a> PreparedCommand<'a> {
                     }
                 };
 
-                Pid::from_raw(child.id() as i32)
+                let child = Pid::from_raw(child.id() as i32);
+                if *pgid == Pid::from_raw(0) {
+                    *pgid = child;
+                }
+
+                // prevent race conditions
+                let _ = unistd::setpgid(child, *pgid);
             }
             CommandKind::Builtin(builtin) => {
-                match unsafe { unistd::fork() }.map_err(RuntimeError::ForkFailed)? {
+                if builtin.nofork {
-                    ForkResult::Parent { child } => child,
+                    self.do_redirects();
-                    ForkResult::Child => {
+                    (builtin.fun)(shell, &self.args);
-                        fn redirect(old: Option<File>, new: RawFd) {
+                } else {
-                            if let Some(old) = old {
+                    match unsafe { unistd::fork() }.map_err(RuntimeError::ForkFailed)? {
-                                let _ = unistd::dup2(old.as_raw_fd(), new);
+                        ForkResult::Parent { child } => {
+                            if *pgid == Pid::from_raw(0) {
+                                *pgid = child;
                             }
+
+                            // prevent race conditions
+                            let _ = unistd::setpgid(child, *pgid);
                         }
+                        ForkResult::Child => {
+                            self.do_redirects();
 
-                        redirect(self.stdin, libc::STDIN_FILENO);
+                            let _ = pre_exec();
-                        redirect(self.stdout, libc::STDOUT_FILENO);
+                            (builtin.fun)(shell, &self.args);
-                        redirect(self.stderr, libc::STDERR_FILENO);
+                            process::exit(0);
-
+                        }
-                        let _ = pre_exec();
-                        (builtin.fun)(shell, &self.args);
-                        process::exit(0);
                     }
                 }
             }
         };
 
-        if *pgid == Pid::from_raw(0) {
+        Ok(())
-            *pgid = child;
+    }
+
+    /// Redirect stdio.
+    fn do_redirects(&self) {
+        fn redirect(old: &Option<File>, new: RawFd) {
+            if let Some(old) = old {
+                let _ = unistd::dup2(old.as_raw_fd(), new);
+            }
         }
 
-        // prevent race conditions
+        redirect(&self.stdin, libc::STDIN_FILENO);
-        let _ = unistd::setpgid(child, *pgid);
+        redirect(&self.stdout, libc::STDOUT_FILENO);
-
+        redirect(&self.stderr, libc::STDERR_FILENO);
-        Ok(())
     }
 }