rumdl_lib/rules/

md050_strong_style.rs

use crate::rule::{Fix, LintError, LintResult, LintWarning, Rule, RuleCategory, Severity};
use crate::rules::strong_style::StrongStyle;
use crate::utils::code_block_utils::StrongSpanDetail;
use crate::utils::skip_context::EmphasisContext;
use regex::Regex;
use std::sync::LazyLock;

static UNICODE_PUNCTUATION: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"^[\p{P}\p{S}]$").unwrap());

/// Unlike asterisks, underscores cannot delimit strong emphasis within a word.
/// Include adjoining underscores when checking the resulting delimiter run.
fn can_use_underscore_strong(content: &str, start: usize, end: usize) -> bool {
    let allows_boundary = |ch: char| {
        ch.is_whitespace()
            || ch.is_ascii_punctuation()
            || (!ch.is_ascii() && UNICODE_PUNCTUATION.is_match(ch.encode_utf8(&mut [0; 4])))
    };
    content[..start]
        .trim_end_matches('_')
        .chars()
        .next_back()
        .is_none_or(allows_boundary)
        && content[end..]
            .trim_start_matches('_')
            .chars()
            .next()
            .is_none_or(allows_boundary)
}

/// Convert a StrongSpanDetail to a StrongStyle
fn span_style(span: &StrongSpanDetail) -> StrongStyle {
    if span.is_asterisk {
        StrongStyle::Asterisk
    } else {
        StrongStyle::Underscore
    }
}

mod md050_config;
use md050_config::MD050Config;

/// Rule MD050: Strong style
///
/// See [docs/md050.md](../../docs/md050.md) for full documentation, configuration, and examples.
///
/// This rule is triggered when strong markers (** or __) are used in an inconsistent way.
#[derive(Debug, Default, Clone)]
pub struct MD050StrongStyle {
    config: MD050Config,
}

impl MD050StrongStyle {
    pub fn new(style: StrongStyle) -> Self {
        Self {
            config: MD050Config { style },
        }
    }

    pub fn from_config_struct(config: MD050Config) -> Self {
        Self { config }
    }

    #[cfg(test)]
    fn detect_style(&self, ctx: &crate::lint_context::LintContext) -> Option<StrongStyle> {
        self.detect_style_from_spans(&mut EmphasisContext::new(ctx), &ctx.strong_spans)
    }

    fn detect_style_from_spans(
        &self,
        context: &mut EmphasisContext<'_, '_>,
        spans: &[StrongSpanDetail],
    ) -> Option<StrongStyle> {
        let mut asterisk_count = 0;
        let mut underscore_count = 0;

        for span in spans {
            if context.should_skip(span.start, span.end) {
                continue;
            }

            match span_style(span) {
                StrongStyle::Asterisk => asterisk_count += 1,
                StrongStyle::Underscore => underscore_count += 1,
                StrongStyle::Consistent => {}
            }
        }

        match (asterisk_count, underscore_count) {
            (0, 0) => None,
            (_, 0) => Some(StrongStyle::Asterisk),
            (0, _) => Some(StrongStyle::Underscore),
            // In case of a tie, prefer asterisk (matches CommonMark recommendation)
            (a, u) => {
                if a >= u {
                    Some(StrongStyle::Asterisk)
                } else {
                    Some(StrongStyle::Underscore)
                }
            }
        }
    }
}

impl Rule for MD050StrongStyle {
    fn native_format_policy(&self) -> Option<crate::format_proof::NativeFormatPolicy> {
        (self.config == Default::default()).then_some(crate::format_proof::NativeFormatPolicy::for_rule::<Self>(50))
    }

    fn name(&self) -> &'static str {
        "MD050"
    }

    fn description(&self) -> &'static str {
        "Strong emphasis style should be consistent"
    }

    fn category(&self) -> RuleCategory {
        RuleCategory::Emphasis
    }

    fn check(&self, ctx: &crate::lint_context::LintContext) -> LintResult {
        let content = ctx.content;

        let mut warnings = Vec::new();

        let spans = &ctx.strong_spans;
        let mut context = EmphasisContext::new(ctx);

        let target_style = match self.config.style {
            StrongStyle::Consistent => self
                .detect_style_from_spans(&mut context, spans)
                .unwrap_or(StrongStyle::Asterisk),
            _ => self.config.style,
        };

        for span in spans {
            // Only flag spans that use the wrong style
            if span_style(span) == target_style {
                continue;
            }

            // Skip too-short spans
            if span.end - span.start < 4 {
                continue;
            }

            // Only check skip context for wrong-style spans (the minority)
            if context.should_skip(span.start, span.end) {
                continue;
            }

            let inner_text = &content[span.start + 2..span.end - 2];

            // NOTE: Intentional deviation from markdownlint behavior.
            // markdownlint reports two warnings per emphasis (one for opening marker,
            // one for closing marker). We report one warning per emphasis block because:
            // 1. The markers are semantically one unit - you can't fix one without the other
            // 2. Cleaner output - "10 issues" vs "20 issues" for 10 bold words
            // 3. The fix is atomic - replacing the entire emphasis at once
            let message = match target_style {
                StrongStyle::Asterisk => "Strong emphasis should use ** instead of __",
                StrongStyle::Underscore => "Strong emphasis should use __ instead of **",
                StrongStyle::Consistent => "Strong emphasis should use ** instead of __",
            };

            let (start_line, start_col, end_line, end_col) = context.single_line_range(span.start, span.end);

            let fix = if target_style == StrongStyle::Underscore
                && !can_use_underscore_strong(content, span.start, span.end)
            {
                None
            } else {
                Some(Fix::new(
                    span.start..span.end,
                    match target_style {
                        StrongStyle::Underscore => format!("__{inner_text}__"),
                        _ => format!("**{inner_text}**"),
                    },
                ))
            };

            warnings.push(LintWarning {
                rule_name: Some(self.name().to_string()),
                line: start_line,
                column: start_col,
                end_line,
                end_column: end_col,
                message: message.to_string(),
                severity: Severity::Warning,
                fix,
            });
        }

        Ok(warnings)
    }

    fn fixes_from_diagnostics(&self) -> bool {
        true
    }

    fn fix(&self, ctx: &crate::lint_context::LintContext) -> Result<String, LintError> {
        if self.should_skip(ctx) {
            return Ok(ctx.content.to_string());
        }
        let warnings = self.check(ctx)?;
        if warnings.is_empty() {
            return Ok(ctx.content.to_string());
        }
        let warnings =
            crate::utils::fix_utils::filter_warnings_by_inline_config(warnings, ctx.inline_config(), self.name());
        crate::utils::fix_utils::apply_warning_fixes(ctx.content, &warnings)
            .map_err(crate::rule::LintError::InvalidInput)
    }

    /// Check if this rule should be skipped
    fn should_skip(&self, ctx: &crate::lint_context::LintContext) -> bool {
        // Strong uses double markers, but likely_has_emphasis checks for count > 1
        ctx.content.is_empty() || !ctx.likely_has_emphasis()
    }

    fn as_any(&self) -> &dyn std::any::Any {
        self
    }

    crate::impl_rule_config_methods!(MD050Config);
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::lint_context::LintContext;

    #[test]
    fn test_shortcode_markers_are_not_restyled() {
        for (style, original, replacement) in [
            (StrongStyle::Underscore, "**", "__"),
            (StrongStyle::Asterisk, "__", "**"),
        ] {
            let rule = MD050StrongStyle::new(style);
            for shortcode in [
                format!("{{{{< note title=\"{original}literal{original}\" >}}}}"),
                format!("{{{{% note title=\"{original}内容{original}\" %}}}}"),
                format!("{{{{< note\n title=\"{original}literal{original}\" >}}}}"),
                format!("{original}text {{{{< note title=\"{original}\" >}}}}"),
            ] {
                let source = format!("Before {shortcode}\n\n{original}visible{original}\n");
                let expected = format!("Before {shortcode}\n\n{replacement}visible{replacement}\n");
                let ctx = crate::lint_context::LintContext::new(&source, crate::config::MarkdownFlavor::Hugo, None);
                assert_eq!(
                    rule.check(&ctx).unwrap().len(),
                    1,
                    "shortcode arguments are literal: {source}"
                );
                assert_eq!(rule.fix(&ctx).unwrap(), expected);
            }
        }
    }

    #[test]
    fn test_shortcode_arguments_do_not_determine_consistent_style() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let source = "Before {{< note title=\"**a** **b** **c**\" >}}\n\n__first__ __second__ **visible**\n";
        let expected = "Before {{< note title=\"**a** **b** **c**\" >}}\n\n__first__ __second__ __visible__\n";
        let ctx = crate::lint_context::LintContext::new(source, crate::config::MarkdownFlavor::Hugo, None);
        assert_eq!(rule.check(&ctx).unwrap().len(), 1);
        assert_eq!(rule.fix(&ctx).unwrap(), expected);
    }

    #[test]
    fn test_myst_comments_do_not_determine_consistent_style() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let source = "% **a** **b** **c**\n\n__first__ __second__ **visible**\n";
        let expected = "% **a** **b** **c**\n\n__first__ __second__ __visible__\n";
        let ctx = crate::lint_context::LintContext::new(source, crate::config::MarkdownFlavor::MyST, None);
        assert_eq!(rule.check(&ctx).unwrap().len(), 1);
        assert_eq!(rule.fix(&ctx).unwrap(), expected);
    }

    #[test]
    fn test_myst_comment_contents_are_not_linted() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        for prefix in ["% ", "%", "  %\t", "   % "] {
            let source = format!("{prefix}**literal**\n\nBefore **visible**\n");
            let expected = format!("{prefix}**literal**\n\nBefore __visible__\n");
            let ctx = crate::lint_context::LintContext::new(&source, crate::config::MarkdownFlavor::MyST, None);
            let warnings = rule.check(&ctx).unwrap();
            assert_eq!(warnings.len(), 1, "comments are not visible prose: {source}");
            assert_eq!(warnings[0].line, 3);
            assert_eq!(rule.fix(&ctx).unwrap(), expected);
        }
    }

    #[test]
    fn test_jinja_quoted_markers_are_not_restyled() {
        for (style, original, replacement) in [
            (StrongStyle::Underscore, "**", "__"),
            (StrongStyle::Asterisk, "__", "**"),
        ] {
            let rule = MD050StrongStyle::new(style);
            for template in [
                format!("{{{{ \"{original}literal{original}\" }}}}"),
                format!("{{% set text = '{original}内容{original}' %}}"),
                format!("{{{{\n  \"{original}literal{original}\"\n}}}}"),
                format!("{original}text {{{{ \"{original}\" }}}}"),
            ] {
                let source = format!("Before {template}\n\n{original}visible{original}\n");
                let expected = format!("Before {template}\n\n{replacement}visible{replacement}\n");
                let ctx = crate::lint_context::LintContext::new(&source, crate::config::MarkdownFlavor::Standard, None);
                assert_eq!(
                    rule.check(&ctx).unwrap().len(),
                    1,
                    "quoted markers are literal: {source}"
                );
                assert_eq!(rule.fix(&ctx).unwrap(), expected);
            }
        }
    }

    #[test]
    fn test_jinja_quoted_markers_do_not_determine_consistent_style() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let source = "Before {{ \"**a** **b** **c**\" }}\n\n__first__ __second__ **visible**\n";
        let expected = "Before {{ \"**a** **b** **c**\" }}\n\n__first__ __second__ __visible__\n";
        let ctx = crate::lint_context::LintContext::new(source, crate::config::MarkdownFlavor::Standard, None);
        assert_eq!(rule.check(&ctx).unwrap().len(), 1);
        assert_eq!(rule.fix(&ctx).unwrap(), expected);
    }

    #[test]
    fn test_mdx_module_strings_are_not_restyled() {
        for (style, original, replacement) in [
            (StrongStyle::Underscore, "**", "__"),
            (StrongStyle::Asterisk, "__", "**"),
        ] {
            let rule = MD050StrongStyle::new(style);
            for module in [
                format!("export const text = \"{original}literal{original}\""),
                format!("export const data = {{\n  text: \"{original}内容{original}\"\n}}"),
                format!("import text from \"./{original}literal{original}.js\""),
            ] {
                let source = format!("{module}\n\n{original}visible{original}\n");
                let expected = format!("{module}\n\n{replacement}visible{replacement}\n");
                let ctx = crate::lint_context::LintContext::new(&source, crate::config::MarkdownFlavor::MDX, None);
                let warnings = rule.check(&ctx).unwrap();
                assert_eq!(warnings.len(), 1, "module strings must stay literal: {source}");
                assert!(warnings[0].line > module.lines().count());
                assert_eq!(rule.fix(&ctx).unwrap(), expected);
            }
        }
    }

    #[test]
    fn test_mdx_module_strings_do_not_determine_consistent_style() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let source = "export const text = \"**a** **b** **c**\"\n\n__first__ __second__ **visible**\n";
        let expected = "export const text = \"**a** **b** **c**\"\n\n__first__ __second__ __visible__\n";
        let ctx = crate::lint_context::LintContext::new(source, crate::config::MarkdownFlavor::MDX, None);
        assert_eq!(rule.check(&ctx).unwrap().len(), 1);
        assert_eq!(rule.fix(&ctx).unwrap(), expected);
    }

    #[test]
    fn test_underscore_style_reports_intraword_strong_without_removing_it() {
        for text in [
            "pre**fix**post",
            "**fix**post",
            "pre**fix**",
            "日本語**強調**後",
            "3**fix**5",
            "foo_**bar**_baz",
        ] {
            let content = format!("__one__ __two__ {text}\n");
            for style in [StrongStyle::Underscore, StrongStyle::Consistent] {
                let rule = MD050StrongStyle::new(style);
                let ctx = LintContext::new(&content, crate::config::MarkdownFlavor::Standard, None);
                let warnings = rule.check(&ctx).unwrap();
                assert_eq!(warnings.len(), 1, "the style mismatch remains visible: {content}");
                assert!(warnings[0].fix.is_none(), "underscores would remove bold: {content}");
                assert_eq!(rule.fix(&ctx).unwrap(), content);
                let mut original_html = String::new();
                pulldown_cmark::html::push_html(&mut original_html, pulldown_cmark::Parser::new(&content));
                assert_eq!(original_html.matches("<strong>").count(), 3);
            }
        }
    }

    #[test]
    fn test_underscore_style_still_fixes_safe_boundaries() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        for (source, expected) in [
            ("**word**", "__word__"),
            ("(**word**)", "(__word__)"),
            ("x-**word**-y", "x-__word__-y"),
            ("“**word**”", "“__word__”"),
            ("💡**word**💡", "💡__word__💡"),
            ("**word**\u{a0}after", "__word__\u{a0}after"),
        ] {
            let ctx = LintContext::new(source, crate::config::MarkdownFlavor::Standard, None);
            let warnings = rule.check(&ctx).unwrap();
            assert_eq!(warnings.len(), 1);
            assert!(warnings[0].fix.is_some());
            assert_eq!(rule.fix(&ctx).unwrap(), expected);
            let fixed_ctx = LintContext::new(expected, crate::config::MarkdownFlavor::Standard, None);
            assert!(rule.check(&fixed_ctx).unwrap().is_empty());
            assert_eq!(rule.fix(&fixed_ctx).unwrap(), expected);
            let mut original_html = String::new();
            let mut fixed_html = String::new();
            pulldown_cmark::html::push_html(&mut original_html, pulldown_cmark::Parser::new(source));
            pulldown_cmark::html::push_html(&mut fixed_html, pulldown_cmark::Parser::new(expected));
            assert_eq!(original_html, fixed_html, "bold formatting must be preserved");
        }
    }

    #[test]
    fn test_underscore_style_fixes_safe_spans_beside_intraword_strong() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let content = "__one__ __two__ __three__ pre**fix**post **safe**\n";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let warnings = rule.check(&ctx).unwrap();
        assert_eq!(warnings.len(), 2);
        assert!(warnings[0].fix.is_none());
        assert!(warnings[1].fix.is_some());
        let expected = "__one__ __two__ __three__ pre**fix**post __safe__\n";
        assert_eq!(rule.fix(&ctx).unwrap(), expected);
        let fixed_ctx = LintContext::new(expected, crate::config::MarkdownFlavor::Standard, None);
        assert_eq!(rule.check(&fixed_ctx).unwrap().len(), 1);
        assert_eq!(rule.fix(&fixed_ctx).unwrap(), expected);
    }

    #[test]
    fn test_asterisk_style_with_asterisks() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is **strong text** here.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 0);
    }

    #[test]
    fn test_asterisk_style_with_underscores() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is __strong text__ here.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 1);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
        assert_eq!(result[0].line, 1);
        assert_eq!(result[0].column, 9);
    }

    #[test]
    fn test_underscore_style_with_underscores() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        let content = "This is __strong text__ here.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 0);
    }

    #[test]
    fn test_underscore_style_with_asterisks() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        let content = "This is **strong text** here.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 1);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use __ instead of **")
        );
    }

    #[test]
    fn test_consistent_style_first_asterisk() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let content = "First **strong** then __also strong__.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // First strong is **, so __ should be flagged
        assert_eq!(result.len(), 1);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
    }

    #[test]
    fn test_consistent_style_tie_prefers_asterisk() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let content = "First __strong__ then **also strong**.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Equal counts (1 vs 1), so prefer asterisks per CommonMark recommendation
        // The __ should be flagged to change to **
        assert_eq!(result.len(), 1);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
    }

    #[test]
    fn test_detect_style_asterisk() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let ctx = LintContext::new(
            "This has **strong** text.",
            crate::config::MarkdownFlavor::Standard,
            None,
        );
        let style = rule.detect_style(&ctx);

        assert_eq!(style, Some(StrongStyle::Asterisk));
    }

    #[test]
    fn test_detect_style_underscore() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let ctx = LintContext::new(
            "This has __strong__ text.",
            crate::config::MarkdownFlavor::Standard,
            None,
        );
        let style = rule.detect_style(&ctx);

        assert_eq!(style, Some(StrongStyle::Underscore));
    }

    #[test]
    fn test_detect_style_none() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let ctx = LintContext::new("No strong text here.", crate::config::MarkdownFlavor::Standard, None);
        let style = rule.detect_style(&ctx);

        assert_eq!(style, None);
    }

    #[test]
    fn test_strong_in_code_block() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "```\n__strong__ in code\n```\n__strong__ outside";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Only the strong outside code block should be flagged
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].line, 4);
    }

    #[test]
    fn test_strong_in_inline_code() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Text with `__strong__` in code and __strong__ outside.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Only the strong outside inline code should be flagged
        assert_eq!(result.len(), 1);
    }

    #[test]
    fn test_escaped_strong() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is \\__not strong\\__ but __this is__.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Only the unescaped strong should be flagged
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].line, 1);
        assert_eq!(result[0].column, 30);
    }

    #[test]
    fn test_fix_asterisks_to_underscores() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        let content = "This is **strong** text.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let fixed = rule.fix(&ctx).unwrap();

        assert_eq!(fixed, "This is __strong__ text.");
    }

    #[test]
    fn test_fix_underscores_to_asterisks() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is __strong__ text.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let fixed = rule.fix(&ctx).unwrap();

        assert_eq!(fixed, "This is **strong** text.");
    }

    #[test]
    fn test_fix_multiple_strong() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "First __strong__ and second __also strong__.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let fixed = rule.fix(&ctx).unwrap();

        assert_eq!(fixed, "First **strong** and second **also strong**.");
    }

    #[test]
    fn test_fix_preserves_code_blocks() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "```\n__strong__ in code\n```\n__strong__ outside";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let fixed = rule.fix(&ctx).unwrap();

        assert_eq!(fixed, "```\n__strong__ in code\n```\n**strong** outside");
    }

    #[test]
    fn test_multiline_content() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Line 1 with __strong__\nLine 2 with __another__\nLine 3 normal";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 2);
        assert_eq!(result[0].line, 1);
        assert_eq!(result[1].line, 2);
    }

    #[test]
    fn test_nested_emphasis() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This has __strong with *emphasis* inside__.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 1);
    }

    #[test]
    fn test_empty_content() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(result.len(), 0);
    }

    #[test]
    fn test_default_config() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let (name, _config) = rule.default_config_section().unwrap();
        assert_eq!(name, "MD050");
    }

    #[test]
    fn test_strong_in_links_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"Instead of assigning to `self.value`, we're relying on the [`__dict__`][__dict__] in our object to hold that value instead.

Hint:

- [An article on something](https://blog.yuo.be/2018/08/16/__init_subclass__-a-simpler-way-to-implement-class-registries-in-python/ "Some details on using `__init_subclass__`")


[__dict__]: https://www.pythonmorsels.com/where-are-attributes-stored/"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // None of the __ patterns in links should be flagged
        assert_eq!(result.len(), 0);
    }

    #[test]
    fn test_strong_in_links_vs_outside_links() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"We're doing this because generator functions return a generator object which [is an iterator][generators are iterators] and **we need `__iter__` to return an [iterator][]**.

Instead of assigning to `self.value`, we're relying on the [`__dict__`][__dict__] in our object to hold that value instead.

This is __real strong text__ that should be flagged.

[__dict__]: https://www.pythonmorsels.com/where-are-attributes-stored/"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Only the real strong text should be flagged, not the __ in links
        assert_eq!(result.len(), 1);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
        // The flagged text should be "real strong text"
        assert!(result[0].line > 4); // Should be on the line with "real strong text"
    }

    #[test]
    fn test_front_matter_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "---\ntitle: What's __init__.py?\nother: __value__\n---\n\nThis __should be flagged__.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Only the strong text outside front matter should be flagged
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].line, 6);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
    }

    #[test]
    fn test_html_tags_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"# Test

This has HTML with underscores:

<iframe src="https://example.com/__init__/__repr__"> </iframe>

This __should be flagged__ as inconsistent."#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();

        // Only the strong text outside HTML tags should be flagged
        assert_eq!(result.len(), 1);
        assert_eq!(result[0].line, 7);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
    }

    #[test]
    fn test_mkdocs_keys_notation_not_flagged() {
        // Keys notation uses ++ which shouldn't be flagged as strong emphasis
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Press ++ctrl+alt+del++ to restart.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        // Keys notation should not be flagged as strong emphasis
        assert!(
            result.is_empty(),
            "Keys notation should not be flagged as strong emphasis. Got: {result:?}"
        );
    }

    #[test]
    fn test_mkdocs_caret_notation_not_flagged() {
        // Insert notation (^^text^^) should not be flagged as strong emphasis
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is ^^inserted^^ text.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        assert!(
            result.is_empty(),
            "Insert notation should not be flagged as strong emphasis. Got: {result:?}"
        );
    }

    #[test]
    fn test_mkdocs_mark_notation_not_flagged() {
        // Mark notation (==highlight==) should not be flagged
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is ==highlighted== text.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        assert!(
            result.is_empty(),
            "Mark notation should not be flagged as strong emphasis. Got: {result:?}"
        );
    }

    #[test]
    fn test_mkdocs_mixed_content_with_real_strong() {
        // Mixed content: MkDocs markup + real strong emphasis that should be flagged
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Press ++ctrl++ and __underscore strong__ here.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        // Only the real underscore strong should be flagged (not Keys notation)
        assert_eq!(result.len(), 1, "Expected 1 warning, got: {result:?}");
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
    }

    #[test]
    fn test_mkdocs_icon_shortcode_not_flagged() {
        // Icon shortcodes like :material-star: should not affect strong detection
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Click :material-check: and __this should be flagged__.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        // The underscore strong should still be flagged
        assert_eq!(result.len(), 1);
        assert!(
            result[0]
                .message
                .contains("Strong emphasis should use ** instead of __")
        );
    }

    #[test]
    fn test_math_block_not_flagged() {
        // Math blocks contain _ and * characters that are not emphasis
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"# Math Section

$$
E = mc^2
x_1 + x_2 = y
a**b = c
$$

This __should be flagged__ outside math.
"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Quarto, None);
        let result = rule.check(&ctx).unwrap();

        // Only the strong outside math block should be flagged
        assert_eq!(result.len(), 1, "Expected 1 warning, got: {result:?}");
        assert!(result[0].line > 7, "Warning should be on line after math block");
    }

    #[test]
    fn test_math_block_with_underscores_not_flagged() {
        // LaTeX subscripts use underscores that shouldn't be flagged
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"$$
x_1 + x_2 + x__3 = y
\alpha__\beta
$$
"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Quarto, None);
        let result = rule.check(&ctx).unwrap();

        // Nothing should be flagged - all content is in math block
        assert!(
            result.is_empty(),
            "Math block content should not be flagged. Got: {result:?}"
        );
    }

    #[test]
    fn test_math_block_with_asterisks_not_flagged() {
        // LaTeX multiplication uses asterisks that shouldn't be flagged
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        let content = r#"$$
a**b = c
2 ** 3 = 8
x***y
$$
"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Quarto, None);
        let result = rule.check(&ctx).unwrap();

        // Nothing should be flagged - all content is in math block
        assert!(
            result.is_empty(),
            "Math block content should not be flagged. Got: {result:?}"
        );
    }

    #[test]
    fn test_math_block_fix_preserves_content() {
        // Fix should not modify content inside math blocks
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"$$
x__y = z
$$

This __word__ should change.
"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Quarto, None);
        let fixed = rule.fix(&ctx).unwrap();

        // Math block content should be unchanged
        assert!(fixed.contains("x__y = z"), "Math block content should be preserved");
        // Strong outside should be fixed
        assert!(fixed.contains("**word**"), "Strong outside math should be fixed");
    }

    #[test]
    fn test_inline_math_simple() {
        // Simple inline math without underscore patterns that could be confused with strong
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "The formula $E = mc^2$ is famous and __this__ is strong.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Quarto, None);
        let result = rule.check(&ctx).unwrap();

        // __this__ should be flagged (it's outside the inline math)
        assert_eq!(
            result.len(),
            1,
            "Expected 1 warning for strong outside math. Got: {result:?}"
        );
    }

    #[test]
    fn test_multiple_math_blocks_and_strong() {
        // Test with multiple math blocks and strong emphasis between them
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = r#"# Document

$$
a = b
$$

This __should be flagged__ text.

$$
c = d
$$
"#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Quarto, None);
        let result = rule.check(&ctx).unwrap();

        // Only the strong between math blocks should be flagged
        assert_eq!(result.len(), 1, "Expected 1 warning. Got: {result:?}");
        assert!(result[0].message.contains("**"));
    }

    #[test]
    fn test_html_tag_skip_consistency_between_check_and_fix() {
        // Verify that check() and fix() share the same HTML tag boundary logic,
        // so double underscores inside HTML attributes are skipped consistently.
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);

        let content = r#"<a href="__test__">link</a>

This __should be flagged__ text."#;
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);

        let check_result = rule.check(&ctx).unwrap();
        let fix_result = rule.fix(&ctx).unwrap();

        // Only the __should be flagged__ outside the HTML tag should be flagged
        assert_eq!(
            check_result.len(),
            1,
            "check() should flag exactly one emphasis outside HTML tags"
        );
        assert!(check_result[0].message.contains("**"));

        // fix() should only transform the same emphasis that check() flagged
        assert!(
            fix_result.contains("**should be flagged**"),
            "fix() should convert the flagged emphasis"
        );
        assert!(
            fix_result.contains("__test__"),
            "fix() should not modify emphasis inside HTML tags"
        );
    }

    #[test]
    fn test_detect_style_ignores_emphasis_in_inline_code_on_table_lines() {
        // In Consistent mode, detect_style() should not count emphasis markers
        // inside inline code spans on table cell lines, matching check() and fix().
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);

        // The only real emphasis is **real** (asterisks). The __code__ inside
        // backtick code spans should be ignored by detect_style().
        let content = "| `__code__` | **real** |\n| --- | --- |\n| data | data |";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);

        let style = rule.detect_style(&ctx);
        // Should detect asterisk as the dominant style (underscore inside code is skipped)
        assert_eq!(style, Some(StrongStyle::Asterisk));
    }

    #[test]
    fn test_five_underscores_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is a series of underscores: _____";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();
        assert!(
            result.is_empty(),
            "_____ should not be flagged as strong emphasis. Got: {result:?}"
        );
    }

    #[test]
    fn test_five_asterisks_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        let content = "This is a series of asterisks: *****";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();
        assert!(
            result.is_empty(),
            "***** should not be flagged as strong emphasis. Got: {result:?}"
        );
    }

    #[test]
    fn test_five_underscores_with_frontmatter_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "---\ntitle: Level 1 heading\n---\n\nThis is a series of underscores: _____\n";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();
        assert!(result.is_empty(), "_____ should not be flagged. Got: {result:?}");
    }

    #[test]
    fn test_four_underscores_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "This is: ____";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();
        assert!(result.is_empty(), "____ should not be flagged. Got: {result:?}");
    }

    #[test]
    fn test_four_asterisks_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Underscore);
        let content = "This is: ****";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();
        assert!(result.is_empty(), "**** should not be flagged. Got: {result:?}");
    }

    #[test]
    fn test_detect_style_ignores_underscore_sequences() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let content = "This is: _____ and also **real bold**";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let style = rule.detect_style(&ctx);
        assert_eq!(style, Some(StrongStyle::Asterisk));
    }

    #[test]
    fn test_fix_does_not_modify_underscore_sequences() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Some _____ sequence and __real bold__ text.";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let fixed = rule.fix(&ctx).unwrap();
        assert!(fixed.contains("_____"), "_____ should be preserved");
        assert!(fixed.contains("**real bold**"), "Real bold should be converted");
    }

    #[test]
    fn test_six_or_more_consecutive_markers_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        for count in [6, 7, 8, 10] {
            let underscores = "_".repeat(count);
            let asterisks = "*".repeat(count);
            let content_u = format!("Text with {underscores} here");
            let content_a = format!("Text with {asterisks} here");

            let ctx_u = LintContext::new(&content_u, crate::config::MarkdownFlavor::Standard, None);
            let ctx_a = LintContext::new(&content_a, crate::config::MarkdownFlavor::Standard, None);

            let result_u = rule.check(&ctx_u).unwrap();
            let result_a = rule.check(&ctx_a).unwrap();

            assert!(
                result_u.is_empty(),
                "{count} underscores should not be flagged. Got: {result_u:?}"
            );
            assert!(
                result_a.is_empty(),
                "{count} asterisks should not be flagged. Got: {result_a:?}"
            );
        }
    }

    #[test]
    fn test_mkdocstrings_block_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "# Example\n\nWe have here some **bold text**.\n\n::: my_module.MyClass\n    options:\n      members:\n        - __init__\n";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        assert!(
            result.is_empty(),
            "__init__ inside mkdocstrings block should not be flagged. Got: {result:?}"
        );
    }

    #[test]
    fn test_mkdocstrings_block_fix_preserves_content() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "# Example\n\nWe have here some **bold text**.\n\n::: my_module.MyClass\n    options:\n      members:\n        - __init__\n        - __repr__\n";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let fixed = rule.fix(&ctx).unwrap();

        assert!(
            fixed.contains("__init__"),
            "__init__ in mkdocstrings block should be preserved"
        );
        assert!(
            fixed.contains("__repr__"),
            "__repr__ in mkdocstrings block should be preserved"
        );
        assert!(fixed.contains("**bold text**"), "Real bold text should be unchanged");
    }

    #[test]
    fn test_mkdocstrings_block_with_strong_outside() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "::: my_module.MyClass\n    options:\n      members:\n        - __init__\n\nThis __should be flagged__ outside.\n";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::MkDocs, None);
        let result = rule.check(&ctx).unwrap();

        assert_eq!(
            result.len(),
            1,
            "Only strong outside mkdocstrings should be flagged. Got: {result:?}"
        );
        assert_eq!(result[0].line, 6);
    }

    #[test]
    fn test_thematic_break_not_flagged() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        let content = "Before\n\n*****\n\nAfter";
        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
        let result = rule.check(&ctx).unwrap();
        assert!(
            result.is_empty(),
            "Thematic break (*****) should not be flagged. Got: {result:?}"
        );

        let content2 = "Before\n\n_____\n\nAfter";
        let ctx2 = LintContext::new(content2, crate::config::MarkdownFlavor::Standard, None);
        let result2 = rule.check(&ctx2).unwrap();
        assert!(
            result2.is_empty(),
            "Thematic break (_____) should not be flagged. Got: {result2:?}"
        );
    }
}

#[cfg(test)]
mod mdx_component_value_tests {
    use super::*;
    #[test]
    fn md050_mdx_component_values_are_literal() {
        let rule = MD050StrongStyle::new(StrongStyle::Asterisk);
        for name in ["span", "Card", "ui.Card", "svg:path"] {
            let tag = format!("<{name} title='__literal__'>text</{name}>");
            let source = format!("内容 Before {tag} after __visible__\n");
            let expected = format!("内容 Before {tag} after **visible**\n");
            let ctx = crate::lint_context::LintContext::new(&source, crate::config::MarkdownFlavor::MDX, None);
            assert_eq!(rule.check(&ctx).unwrap().len(), 1, "{source}");
            assert_eq!(rule.fix(&ctx).unwrap(), expected);
        }
    }
    #[test]
    fn md050_mdx_literals_do_not_choose_consistent_style() {
        let rule = MD050StrongStyle::new(StrongStyle::Consistent);
        let source =
            "Before <ui.Card title='**a** **b** **c**'>text</ui.Card> after\n\n__first__ __second__ **visible**\n";
        let expected = source.replace("**visible**", "__visible__");
        let ctx = crate::lint_context::LintContext::new(source, crate::config::MarkdownFlavor::MDX, None);
        assert_eq!(rule.check(&ctx).unwrap().len(), 1);
        assert_eq!(rule.fix(&ctx).unwrap(), expected);
    }
}