subshells

src/ast.rs

@@ -9,4 +9,6 @@ pub enum Ast {
     And { left: Box<Ast>, right: Box<Ast> },
     Or { left: Box<Ast>, right: Box<Ast> },
     Sequence { left: Box<Ast>, right: Box<Ast> },
+    Subshell { inner: Box<Ast> },
+    Empty,
 }

src/bin/shell.rs

@@ -11,7 +11,7 @@ fn main() {
 
         io::stdin().lock().read_line(&mut line).unwrap();
 
-        if let Err(e) = Pipeline::run(&line) {
+        if let Err(e) = Pipeline::run(line.trim()) {
             eprintln!("Error: {}", e);
         }
 

src/exec.rs

@@ -19,6 +19,8 @@ fn exec_impl(ast: &Ast, stdin: Option<Stdio>, stdout: Option<Stdio>) -> io::Resu
         Ast::And { left, right } => exec_and(left, right, stdout),
         Ast::Or { left, right } => exec_or(left, right, stdout),
         Ast::Sequence { left, right } => exec_sequence(left, right, stdout),
+        Ast::Subshell { inner } => exec_impl(inner, stdin, stdout),
+        Ast::Empty => Ok(Command::new("true").spawn()?),
     }
 }
 
@@ -254,6 +256,26 @@ mod tests {
         assert_eq!(std::str::from_utf8(&output.stdout).unwrap(), "bar\n");
     }
 
+    #[test]
+    fn test_exec_impl_subshells() {
+        let ast = Ast::Subshell {
+            inner: Box::new(Ast::Subshell {
+                inner: Box::new(Ast::Subshell {
+                    inner: Box::new(Ast::Subshell {
+                        inner: Box::new(Ast::Command {
+                            command: input!("echo"),
+                            args: vec![input!("foo")],
+                        }),
+                    }),
+                }),
+            }),
+        };
+        let stdout = Stdio::piped();
+        let child = exec_impl(&ast, None, Some(stdout)).unwrap();
+        let output = child.wait_with_output().unwrap();
+        assert_eq!(std::str::from_utf8(&output.stdout).unwrap(), "foo\n");
+    }
+
     #[test]
     fn test_exec_impl_with_pipe() {
         let ast = Ast::Pipe {

src/grammar.rs

@@ -11,8 +11,9 @@ pub enum Token {
     And,
     Or,
     End,
+    OpenParenthesis,
+    CloseParenthesis,
     // TODO:
-    // - Subshell
     // - Variable
 }
 
@@ -28,6 +29,8 @@ impl AsRef<OsStr> for Token {
             Token::Or => "||".as_ref(),
             Token::Background => "&".as_ref(),
             Token::End => ";".as_ref(),
+            Token::OpenParenthesis => "(".as_ref(),
+            Token::CloseParenthesis => ")".as_ref(),
         }
     }
 }

src/lex.rs

@@ -92,6 +92,16 @@ impl Lexer {
                     tokens.push(input!(std::mem::take(&mut token)));
                 }
                 tokens.push(Token::RedirectIn);
+            } else if c == '(' && !in_single_quotes && !in_double_quotes {
+                if !token.is_empty() {
+                    tokens.push(input!(std::mem::take(&mut token)));
+                }
+                tokens.push(Token::OpenParenthesis);
+            } else if c == ')' && !in_single_quotes && !in_double_quotes {
+                if !token.is_empty() {
+                    tokens.push(input!(std::mem::take(&mut token)));
+                }
+                tokens.push(Token::CloseParenthesis);
             } else {
                 token.push(c);
             }