Merge pull request #7974 from frendsick/fix/expr-regex-special-cases

expr: Handle more special cases for regex pattern

Author: cakebaker

src/uu/expr/src/expr.rs

@@ -50,6 +50,8 @@ pub enum ExprError {
     UnmatchedClosingBrace,
     #[error("Invalid content of \\{{\\}}")]
     InvalidBracketContent,
+    #[error("Trailing backslash")]
+    TrailingBackslash,
 }
 
 impl UError for ExprError {

src/uu/expr/src/syntax_tree.rs

@@ -161,6 +161,8 @@ impl StringOp {
                 match first {
                     Some('^') => {} // Start of string anchor is already added
                     Some('*') => re_string.push_str(r"\*"),
+                    Some('$') if !is_end_of_expression(&pattern_chars) => re_string.push_str(r"\$"),
+                    Some('\\') if right.len() == 1 => return Err(ExprError::TrailingBackslash),
                     Some(char) => re_string.push(char),
                     None => return Ok(0.into()),
                 };
@@ -169,6 +171,8 @@ impl StringOp {
                 let mut prev = first.unwrap_or_default();
                 let mut prev_is_escaped = false;
                 while let Some(curr) = pattern_chars.next() {
+                    let curr_is_escaped = prev == '\\' && !prev_is_escaped;
+
                     match curr {
                         '^' => match (prev, prev_is_escaped) {
                             // Start of a capturing group
@@ -181,25 +185,11 @@ impl StringOp {
                             | ('\\', false) => re_string.push(curr),
                             _ => re_string.push_str(r"\^"),
                         },
-                        '$' => {
-                            if let Some('\\') = pattern_chars.peek() {
-                                // The next character was checked to be a backslash
-                                let backslash = pattern_chars.next().unwrap_or_default();
-                                match pattern_chars.peek() {
-                                    // End of a capturing group
-                                    Some(')') => re_string.push('$'),
-                                    // End of an alternative pattern
-                                    Some('|') => re_string.push('$'),
-                                    _ => re_string.push_str(r"\$"),
-                                }
-                                re_string.push(backslash);
-                            } else if (prev_is_escaped || prev != '\\')
-                                && pattern_chars.peek().is_some()
-                            {
-                                re_string.push_str(r"\$");
-                            } else {
-                                re_string.push('$');
-                            }
+                        '$' if !curr_is_escaped && !is_end_of_expression(&pattern_chars) => {
+                            re_string.push_str(r"\$");
+                        }
+                        '\\' if !curr_is_escaped && pattern_chars.peek().is_none() => {
+                            return Err(ExprError::TrailingBackslash);
                         }
                         _ => re_string.push(curr),
                     }
@@ -241,6 +231,19 @@ impl StringOp {
     }
 }
 
+/// Check if regex pattern character iterator is at the end of a regex expression or subexpression
+fn is_end_of_expression<I>(pattern_chars: &I) -> bool
+where
+    I: Iterator<Item = char> + Clone,
+{
+    let mut pattern_chars_clone = pattern_chars.clone();
+    match pattern_chars_clone.next() {
+        Some('\\') => matches!(pattern_chars_clone.next(), Some(')' | '|')),
+        None => true, // No characters left
+        _ => false,
+    }
+}
+
 /// Check for errors in a supplied regular expression
 ///
 /// GNU coreutils shows messages for invalid regular expressions

tests/by-util/test_expr.rs

@@ -273,35 +273,44 @@ fn test_length_mb() {
 }
 
 #[test]
-fn test_regex() {
-    new_ucmd!()
-        .args(&["a^b", ":", "a^b"])
-        .succeeds()
-        .stdout_only("3\n");
+fn test_regex_empty() {
+    new_ucmd!().args(&["", ":", ""]).fails().stdout_only("0\n");
     new_ucmd!()
-        .args(&["a^b", ":", "a\\^b"])
-        .succeeds()
-        .stdout_only("3\n");
+        .args(&["abc", ":", ""])
+        .fails()
+        .stdout_only("0\n");
+}
+
+#[test]
+fn test_regex_trailing_backslash() {
     new_ucmd!()
-        .args(&["b", ":", "a\\|^b"])
+        .args(&["\\", ":", "\\\\"])
         .succeeds()
         .stdout_only("1\n");
     new_ucmd!()
-        .args(&["ab", ":", "\\(^a\\)b"])
-        .succeeds()
-        .stdout_only("a\n");
+        .args(&["\\", ":", "\\"])
+        .fails()
+        .stderr_only("expr: Trailing backslash\n");
     new_ucmd!()
-        .args(&["a$b", ":", "a\\$b"])
+        .args(&["abc\\", ":", "abc\\\\"])
         .succeeds()
-        .stdout_only("3\n");
+        .stdout_only("4\n");
     new_ucmd!()
-        .args(&["a", ":", "a$\\|b"])
+        .args(&["abc\\", ":", "abc\\"])
+        .fails()
+        .stderr_only("expr: Trailing backslash\n");
+}
+
+#[test]
+fn test_regex_caret() {
+    new_ucmd!()
+        .args(&["a^b", ":", "a^b"])
         .succeeds()
-        .stdout_only("1\n");
+        .stdout_only("3\n");
     new_ucmd!()
-        .args(&["ab", ":", "a\\(b$\\)"])
+        .args(&["a^b", ":", "a\\^b"])
         .succeeds()
-        .stdout_only("b\n");
+        .stdout_only("3\n");
     new_ucmd!()
         .args(&["abc", ":", "^abc"])
         .succeeds()
@@ -311,13 +320,17 @@ fn test_regex() {
         .succeeds()
         .stdout_only("4\n");
     new_ucmd!()
-        .args(&["b^$ic", ":", "b^\\$ic"])
+        .args(&["b", ":", "a\\|^b"])
         .succeeds()
-        .stdout_only("5\n");
+        .stdout_only("1\n");
     new_ucmd!()
-        .args(&["a$c", ":", "a$\\c"])
+        .args(&["ab", ":", "\\(^a\\)b"])
         .succeeds()
-        .stdout_only("3\n");
+        .stdout_only("a\n");
+    new_ucmd!()
+        .args(&["^abc", ":", "^abc"])
+        .fails()
+        .stdout_only("0\n");
     new_ucmd!()
         .args(&["^^^^^^^^^", ":", "^^^"])
         .succeeds()
@@ -338,29 +351,57 @@ fn test_regex() {
         .args(&["\\a", ":", "\\\\[^^]"])
         .succeeds()
         .stdout_only("2\n");
+    // Patterns are anchored to the beginning of the pattern "^bc"
+    new_ucmd!()
+        .args(&["abc", ":", "bc"])
+        .fails()
+        .stdout_only("0\n");
     new_ucmd!()
         .args(&["^a", ":", "^^[^^]"])
         .succeeds()
         .stdout_only("2\n");
     new_ucmd!()
-        .args(&["-5", ":", "-\\{0,1\\}[0-9]*$"])
+        .args(&["abc", ":", "ab[^c]"])
+        .fails()
+        .stdout_only("0\n");
+}
+
+#[test]
+fn test_regex_dollar() {
+    new_ucmd!()
+        .args(&["a$b", ":", "a\\$b"])
+        .succeeds()
+        .stdout_only("3\n");
+    new_ucmd!()
+        .args(&["a", ":", "a$\\|b"])
+        .succeeds()
+        .stdout_only("1\n");
+    new_ucmd!()
+        .args(&["ab", ":", "a\\(b$\\)"])
+        .succeeds()
+        .stdout_only("b\n");
+    new_ucmd!()
+        .args(&["a$c", ":", "a$\\c"])
+        .succeeds()
+        .stdout_only("3\n");
+    new_ucmd!()
+        .args(&["$a", ":", "$a"])
         .succeeds()
         .stdout_only("2\n");
-    new_ucmd!().args(&["", ":", ""]).fails().stdout_only("0\n");
     new_ucmd!()
-        .args(&["abc", ":", ""])
-        .fails()
-        .stdout_only("0\n");
+        .args(&["a", ":", "a$\\|b"])
+        .succeeds()
+        .stdout_only("1\n");
     new_ucmd!()
-        .args(&["abc", ":", "bc"])
-        .fails()
-        .stdout_only("0\n");
+        .args(&["-5", ":", "-\\{0,1\\}[0-9]*$"])
+        .succeeds()
+        .stdout_only("2\n");
     new_ucmd!()
-        .args(&["^abc", ":", "^abc"])
+        .args(&["$", ":", "$"])
         .fails()
         .stdout_only("0\n");
     new_ucmd!()
-        .args(&["abc", ":", "ab[^c]"])
+        .args(&["a$", ":", "a$\\|b"])
         .fails()
         .stdout_only("0\n");
 }