Merge pull request uutils#5408 from Luv-Ray/fix-expr-syntex-error

`expr`: fix expr syntax error

src/uu/expr/src/tokens.rs

@@ -16,8 +16,6 @@
 
 // spell-checker:ignore (ToDO) paren
 
-use num_bigint::BigInt;
-
 #[derive(Debug, Clone)]
 pub enum Token {
     Value {
@@ -59,11 +57,8 @@ impl Token {
         }
     }
 
-    fn is_a_number(&self) -> bool {
-        match self {
-            Self::Value { value, .. } => value.parse::<BigInt>().is_ok(),
-            _ => false,
-        }
+    fn is_a_value(&self) -> bool {
+        matches!(*self, Self::Value { .. })
     }
 
     fn is_a_close_paren(&self) -> bool {
@@ -131,14 +126,14 @@ fn maybe_dump_tokens_acc(tokens_acc: &[(usize, Token)]) {
 }
 
 fn push_token_if_not_escaped(acc: &mut Vec<(usize, Token)>, tok_idx: usize, token: Token, s: &str) {
-    // Smells heuristics... :(
+    // `+` may be escaped such as `expr + 1` and `expr 1 + + 1`
     let prev_is_plus = match acc.last() {
         None => false,
         Some(t) => t.1.is_infix_plus(),
     };
     let should_use_as_escaped = if prev_is_plus && acc.len() >= 2 {
         let pre_prev = &acc[acc.len() - 2];
-        !(pre_prev.1.is_a_number() || pre_prev.1.is_a_close_paren())
+        !(pre_prev.1.is_a_value() || pre_prev.1.is_a_close_paren())
     } else {
         prev_is_plus
     };

tests/by-util/test_expr.rs

@@ -138,6 +138,11 @@ fn test_or() {
         .args(&["0", "|", "10", "/", "5"])
         .succeeds()
         .stdout_only("2\n");
+
+    new_ucmd!()
+        .args(&["12", "|", "9a", "+", "1"])
+        .succeeds()
+        .stdout_only("12\n");
 }
 
 #[test]
@@ -276,6 +281,26 @@ fn test_invalid_substr() {
         .stdout_only("\n");
 }
 
+#[test]
+fn test_escape() {
+    new_ucmd!().args(&["+", "1"]).succeeds().stdout_only("1\n");
+
+    new_ucmd!()
+        .args(&["1", "+", "+", "1"])
+        .succeeds()
+        .stdout_only("2\n");
+
+    new_ucmd!()
+        .args(&["2", "*", "+", "3"])
+        .succeeds()
+        .stdout_only("6\n");
+
+    new_ucmd!()
+        .args(&["(", "1", ")", "+", "1"])
+        .succeeds()
+        .stdout_only("2\n");
+}
+
 #[test]
 fn test_invalid_syntax() {
     let invalid_syntaxes = [["12", "12"], ["12", "|"], ["|", "12"]];