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use crate::lint::rule::Rule;
use crate::markdown::MarkdownParser;
use crate::types::{Fix, Violation};
use serde_json::Value;
pub struct MD049;
impl Rule for MD049 {
fn name(&self) -> &str {
"MD049"
}
fn description(&self) -> &str {
"Emphasis style should be consistent"
}
fn tags(&self) -> &[&str] {
&["emphasis"]
}
fn check(&self, parser: &MarkdownParser, config: Option<&Value>) -> Vec<Violation> {
let style = config
.and_then(|c| c.get("style"))
.and_then(|v| v.as_str())
.unwrap_or("asterisk");
let mut violations = Vec::new();
let mut first_style: Option<char> = None;
// Get byte ranges that are in code (more precise than line numbers)
let code_ranges = parser.get_code_ranges();
// Helper function to check if a position is within code
let is_in_code = |line_num: usize, byte_offset: usize| -> bool {
let absolute_offset = parser.line_offset_to_absolute(line_num, byte_offset);
code_ranges
.iter()
.any(|range| range.contains(&absolute_offset))
};
for (line_num, line) in parser.lines().iter().enumerate() {
let line_number = line_num + 1;
// Look for emphasis patterns: *text* or _text_ (not ** or __)
let chars: Vec<char> = line.chars().collect();
let mut i = 0;
while i < chars.len() {
let ch = chars[i];
// Check for single * or _ (emphasis, not strong)
if (ch == '*' || ch == '_') && i + 1 < chars.len() {
// Make sure it's not strong (** or __)
let is_strong = (i + 1 < chars.len() && chars[i + 1] == ch)
|| (i > 0 && chars[i - 1] == ch);
// For `_`, apply CommonMark left-flanking rule: the opening `_` must not
// be preceded by an alphanumeric character (spec section 6.2). This
// prevents snake_case words from being treated as emphasis.
let can_open = ch == '*' || i == 0 || !chars[i - 1].is_alphanumeric();
if !is_strong && can_open {
// Find closing marker
for j in (i + 1)..chars.len() {
if chars[j] == ch {
// Make sure closing is also not strong
let close_is_strong = (j + 1 < chars.len() && chars[j + 1] == ch)
|| (j > 0 && chars[j - 1] == ch);
// For `_`, apply CommonMark right-flanking rule: the closing
// `_` must not be followed by an alphanumeric character.
let can_close = ch == '*'
|| j + 1 >= chars.len()
|| !chars[j + 1].is_alphanumeric();
if !close_is_strong && can_close {
// Skip if this emphasis is inside code
if is_in_code(line_number, i) {
i = j; // Skip to after closing
break;
}
// Track style and report violations for both opening and closing
let make_fix = |col: usize, target: char| Fix {
line_start: line_number,
line_end: line_number,
column_start: Some(col),
column_end: Some(col),
replacement: target.to_string(),
description: "Replace emphasis marker".to_string(),
};
if style == "consistent" {
if let Some(first) = first_style {
if ch != first {
violations.push(Violation {
line: line_number,
column: Some(i + 1),
rule: self.name().to_string(),
message: format!(
"Emphasis style should be consistent: expected '{}', found '{}'",
first, ch
),
fix: Some(make_fix(i + 1, first)),
});
violations.push(Violation {
line: line_number,
column: Some(j + 1),
rule: self.name().to_string(),
message: format!(
"Emphasis style should be consistent: expected '{}', found '{}'",
first, ch
),
fix: Some(make_fix(j + 1, first)),
});
}
} else {
first_style = Some(ch);
}
} else {
let expected = if style == "asterisk" { '*' } else { '_' };
if ch != expected {
violations.push(Violation {
line: line_number,
column: Some(i + 1),
rule: self.name().to_string(),
message: format!(
"Emphasis style should be '{}', found '{}'",
expected, ch
),
fix: Some(make_fix(i + 1, expected)),
});
violations.push(Violation {
line: line_number,
column: Some(j + 1),
rule: self.name().to_string(),
message: format!(
"Emphasis style should be '{}', found '{}'",
expected, ch
),
fix: Some(make_fix(j + 1, expected)),
});
}
}
i = j; // Skip to after closing
break;
}
}
}
}
}
i += 1;
}
}
violations
}
fn fixable(&self) -> bool {
true
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_consistent_asterisk() {
let content = "This is *italic* and *more italic*.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let violations = rule.check(&parser, None);
assert_eq!(violations.len(), 0);
}
#[test]
fn test_consistent_underscore() {
let content = "This is _italic_ and _more italic_.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let config = serde_json::json!({ "style": "consistent" });
let violations = rule.check(&parser, Some(&config));
assert_eq!(violations.len(), 0);
}
#[test]
fn test_inconsistent() {
let content = "This is *italic* and _also italic_.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let violations = rule.check(&parser, None);
// Reports violation for both opening and closing markers of the second emphasis
assert_eq!(violations.len(), 2);
}
#[test]
fn test_enforced_style() {
let content = "This is _italic_ text.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let config = serde_json::json!({ "style": "asterisk" });
let violations = rule.check(&parser, Some(&config));
// Reports violation for both opening and closing markers
assert_eq!(violations.len(), 2);
}
#[test]
fn test_code_block_with_underscores() {
let content = "Normal text\n\n```sql\nCREATE POLICY territory_contact_access ON contacts\n FOR SELECT\n USING (\n territory_id IN (\n SELECT territory_id\n FROM user_territory_assignments\n WHERE user_id = current_setting('app.current_user_id')::uuid\n AND (valid_to IS NULL OR valid_to > NOW())\n )\n );\n```\n\nMore text";
let parser = MarkdownParser::new(content);
let rule = MD049;
let violations = rule.check(&parser, None);
// Should not flag underscores in SQL identifiers as emphasis
assert_eq!(violations.len(), 0);
}
#[test]
fn test_inline_code_with_underscores() {
let content = "Use the `user_id` variable in *bold* text.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let violations = rule.check(&parser, None);
// Should not flag underscores in inline code
assert_eq!(violations.len(), 0);
}
#[test]
fn test_snake_case_not_flagged() {
// Underscores inside words (snake_case) must not be treated as emphasis:
// CommonMark spec ยง6.2 says a `_` can only open emphasis when not preceded
// by an alphanumeric character.
let content = "Call offset_to_line, parse_with_offsets(), and heading_line_length.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let violations = rule.check(&parser, None);
assert_eq!(violations.len(), 0);
}
#[test]
fn test_underscore_emphasis_in_punctuation_context() {
// `_italic_` after `(` should still be treated as emphasis.
let content = "See (_italic_) for details.";
let parser = MarkdownParser::new(content);
let rule = MD049;
let config = serde_json::json!({ "style": "asterisk" });
let violations = rule.check(&parser, Some(&config));
assert_eq!(violations.len(), 2);
}
#[test]
fn test_typescript_multiplication() {
let content = "```typescript\nconst result = value_a * value_b * value_c;\n```";
let parser = MarkdownParser::new(content);
let rule = MD049;
let violations = rule.check(&parser, None);
// Should not flag asterisks in code as emphasis markers
assert_eq!(violations.len(), 0);
}
}