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expr: Only '^' requires special treatment at the start of regex

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Teemu Pätsi 2025-05-27 15:26:41 +03:00
parent 210f4f7154
commit ca6a10ea9a
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1 changed files with 13 additions and 17 deletions
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30
src/uu/expr/src/syntax_tree.rs
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@ -151,27 +151,21 @@ impl StringOp {
let right = right?.eval_as_string(); let right = right?.eval_as_string();
check_posix_regex_errors(&right)?; check_posix_regex_errors(&right)?;
// All patterns are anchored so they begin with a caret (^) // Transpile the input pattern from BRE syntax to `onig` crate's `Syntax::grep`
let mut re_string = String::with_capacity(right.len() + 1); let mut re_string = String::with_capacity(right.len() + 1);
re_string.push('^');
// Handle first character from the input pattern
let mut pattern_chars = right.chars().peekable(); let mut pattern_chars = right.chars().peekable();
let first = pattern_chars.next(); let mut prev = '\0';
match first {
Some('^') => {} // Start of string anchor is already added
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()),
};
// Handle the rest of the input pattern.
let mut prev = first.unwrap_or_default();
let mut prev_is_escaped = false; let mut prev_is_escaped = false;
let mut is_start_of_expression = first == Some('\\'); let mut is_start_of_expression = true;
// All patterns are anchored so they begin with a caret (^)
if pattern_chars.peek() != Some(&'^') {
re_string.push('^');
}
while let Some(curr) = pattern_chars.next() { while let Some(curr) = pattern_chars.next() {
let curr_is_escaped = prev == '\\' && !prev_is_escaped; let curr_is_escaped = prev == '\\' && !prev_is_escaped;
let is_first_character = prev == '\0';
match curr { match curr {
// Character class negation "[^a]" // Character class negation "[^a]"
@ -208,8 +202,10 @@ impl StringOp {
// Capturing group "\(abc\)" // Capturing group "\(abc\)"
// Alternative pattern "a\|b" // Alternative pattern "a\|b"
is_start_of_expression = curr_is_escaped && matches!(curr, '(' | '|') is_start_of_expression = curr == '\\' && is_first_character
|| curr_is_escaped && matches!(curr, '(' | '|')
|| curr == '\\' && prev_is_escaped && matches!(prev, '(' | '|'); || curr == '\\' && prev_is_escaped && matches!(prev, '(' | '|');
prev_is_escaped = curr_is_escaped; prev_is_escaped = curr_is_escaped;
prev = curr; prev = curr;
} }