Add ! negation support, fix POSIX exit statuses, and improve vi emulation with comprehensive tests

src/parse/lex.rs

@@ -17,9 +17,9 @@ use crate::{
   },
 };
 
-pub const KEYWORDS: [&str; 16] = [
+pub const KEYWORDS: [&str; 17] = [
   "if", "then", "elif", "else", "fi", "while", "until", "select", "for", "in", "do", "done",
-  "case", "esac", "[[", "]]",
+  "case", "esac", "[[", "]]", "!"
 ];
 
 pub const OPENERS: [&str; 6] = ["if", "while", "until", "for", "select", "case"];
@@ -166,6 +166,7 @@ pub enum TkRule {
   ErrPipe,
   And,
   Or,
+	Bang,
   Bg,
   Sep,
   Redir,
@@ -882,6 +883,14 @@ impl Iterator for LexStream {
           return self.next();
         }
       }
+			'!' if self.next_is_cmd() => {
+				self.cursor += 1;
+				let tk_type = TkRule::Bang;
+
+				let mut tk = self.get_token((self.cursor - 1)..self.cursor, tk_type);
+				tk.flags |= TkFlags::KEYWORD;
+				tk
+			}
       '|' => {
         let ch_idx = self.cursor;
         self.cursor += 1;