rumdl_lib/rules/
md003_heading_style.rs

1//!
2//! Rule MD003: Heading style
3//!
4//! See [docs/md003.md](../../docs/md003.md) for full documentation, configuration, and examples.
5
6use crate::rule::{LintError, LintResult, LintWarning, Rule, RuleCategory, Severity};
7use crate::rule_config_serde::RuleConfig;
8use crate::rules::heading_utils::HeadingStyle;
9use crate::utils::range_utils::calculate_heading_range;
10use toml;
11
12mod md003_config;
13use md003_config::MD003Config;
14
15/// Rule MD003: Heading style
16#[derive(Clone, Default)]
17pub struct MD003HeadingStyle {
18    config: MD003Config,
19}
20
21impl MD003HeadingStyle {
22    pub fn new(style: HeadingStyle) -> Self {
23        Self {
24            config: MD003Config { style },
25        }
26    }
27
28    pub fn from_config_struct(config: MD003Config) -> Self {
29        Self { config }
30    }
31
32    /// Check if we should use consistent mode (detect first style)
33    fn is_consistent_mode(&self) -> bool {
34        // Check for the Consistent variant explicitly
35        self.config.style == HeadingStyle::Consistent
36    }
37
38    /// Gets the target heading style based on configuration and document content
39    fn get_target_style(&self, ctx: &crate::lint_context::LintContext) -> HeadingStyle {
40        if !self.is_consistent_mode() {
41            return self.config.style;
42        }
43
44        // Count all heading styles to determine most prevalent (prevalence-based approach)
45        let mut style_counts = std::collections::HashMap::new();
46
47        for line_info in &ctx.lines {
48            if let Some(heading) = &line_info.heading {
49                // Skip invalid headings (e.g., `#NoSpace` which lacks required space after #)
50                if !heading.is_valid {
51                    continue;
52                }
53
54                // Map from LintContext heading style to rules heading style and count
55                let style = match heading.style {
56                    crate::lint_context::HeadingStyle::ATX => {
57                        if heading.has_closing_sequence {
58                            HeadingStyle::AtxClosed
59                        } else {
60                            HeadingStyle::Atx
61                        }
62                    }
63                    crate::lint_context::HeadingStyle::Setext1 => HeadingStyle::Setext1,
64                    crate::lint_context::HeadingStyle::Setext2 => HeadingStyle::Setext2,
65                };
66                *style_counts.entry(style).or_insert(0) += 1;
67            }
68        }
69
70        // Return most prevalent style
71        // In case of tie, prefer ATX as the default (deterministic tiebreaker)
72        style_counts
73            .into_iter()
74            .max_by(|(style_a, count_a), (style_b, count_b)| {
75                match count_a.cmp(count_b) {
76                    std::cmp::Ordering::Equal => {
77                        // Tiebreaker: prefer ATX (most common), then Setext1, then Setext2, then AtxClosed
78                        let priority = |s: &HeadingStyle| match s {
79                            HeadingStyle::Atx => 0,
80                            HeadingStyle::Setext1 => 1,
81                            HeadingStyle::Setext2 => 2,
82                            HeadingStyle::AtxClosed => 3,
83                            _ => 4,
84                        };
85                        priority(style_b).cmp(&priority(style_a)) // Reverse for min priority wins
86                    }
87                    other => other,
88                }
89            })
90            .map(|(style, _)| style)
91            .unwrap_or(HeadingStyle::Atx)
92    }
93}
94
95impl Rule for MD003HeadingStyle {
96    fn name(&self) -> &'static str {
97        "MD003"
98    }
99
100    fn description(&self) -> &'static str {
101        "Heading style"
102    }
103
104    fn check(&self, ctx: &crate::lint_context::LintContext) -> LintResult {
105        let mut result = Vec::new();
106
107        // Get the target style using cached heading information
108        let target_style = self.get_target_style(ctx);
109
110        // Process headings using cached heading information
111        for (line_num, line_info) in ctx.lines.iter().enumerate() {
112            if let Some(heading) = &line_info.heading {
113                // Skip invalid headings (e.g., `#NoSpace` which lacks required space after #)
114                if !heading.is_valid {
115                    continue;
116                }
117
118                let level = heading.level;
119
120                // Map the cached heading style to the rule's HeadingStyle
121                let current_style = match heading.style {
122                    crate::lint_context::HeadingStyle::ATX => {
123                        if heading.has_closing_sequence {
124                            HeadingStyle::AtxClosed
125                        } else {
126                            HeadingStyle::Atx
127                        }
128                    }
129                    crate::lint_context::HeadingStyle::Setext1 => HeadingStyle::Setext1,
130                    crate::lint_context::HeadingStyle::Setext2 => HeadingStyle::Setext2,
131                };
132
133                // Determine expected style based on level and target
134                let expected_style = match target_style {
135                    HeadingStyle::Setext1 | HeadingStyle::Setext2 => {
136                        if level > 2 {
137                            // Setext only supports levels 1-2, so levels 3+ must be ATX
138                            HeadingStyle::Atx
139                        } else if level == 1 {
140                            HeadingStyle::Setext1
141                        } else {
142                            HeadingStyle::Setext2
143                        }
144                    }
145                    HeadingStyle::SetextWithAtx => {
146                        if level <= 2 {
147                            // Use Setext for h1/h2
148                            if level == 1 {
149                                HeadingStyle::Setext1
150                            } else {
151                                HeadingStyle::Setext2
152                            }
153                        } else {
154                            // Use ATX for h3-h6
155                            HeadingStyle::Atx
156                        }
157                    }
158                    HeadingStyle::SetextWithAtxClosed => {
159                        if level <= 2 {
160                            // Use Setext for h1/h2
161                            if level == 1 {
162                                HeadingStyle::Setext1
163                            } else {
164                                HeadingStyle::Setext2
165                            }
166                        } else {
167                            // Use ATX closed for h3-h6
168                            HeadingStyle::AtxClosed
169                        }
170                    }
171                    _ => target_style,
172                };
173
174                if current_style != expected_style {
175                    // Generate fix for this heading
176                    let fix = {
177                        use crate::rules::heading_utils::HeadingUtils;
178
179                        // Convert heading to target style, preserving inline attribute lists
180                        let converted_heading =
181                            HeadingUtils::convert_heading_style(&heading.raw_text, level as u32, expected_style);
182
183                        // Preserve original indentation (including tabs)
184                        let line = line_info.content(ctx.content);
185                        let original_indent = &line[..line_info.indent];
186                        let final_heading = format!("{original_indent}{converted_heading}");
187
188                        // Calculate the correct range for the heading
189                        let range = ctx.line_index.line_content_range(line_num + 1);
190
191                        Some(crate::rule::Fix {
192                            range,
193                            replacement: final_heading,
194                        })
195                    };
196
197                    // Calculate precise character range for the heading marker
198                    let (start_line, start_col, end_line, end_col) =
199                        calculate_heading_range(line_num + 1, line_info.content(ctx.content));
200
201                    result.push(LintWarning {
202                        rule_name: Some(self.name().to_string()),
203                        line: start_line,
204                        column: start_col,
205                        end_line,
206                        end_column: end_col,
207                        message: format!(
208                            "Heading style should be {}, found {}",
209                            match expected_style {
210                                HeadingStyle::Atx => "# Heading",
211                                HeadingStyle::AtxClosed => "# Heading #",
212                                HeadingStyle::Setext1 => "Heading\n=======",
213                                HeadingStyle::Setext2 => "Heading\n-------",
214                                HeadingStyle::Consistent => "consistent with the first heading",
215                                HeadingStyle::SetextWithAtx => "setext-with-atx style",
216                                HeadingStyle::SetextWithAtxClosed => "setext-with-atx-closed style",
217                            },
218                            match current_style {
219                                HeadingStyle::Atx => "# Heading",
220                                HeadingStyle::AtxClosed => "# Heading #",
221                                HeadingStyle::Setext1 => "Heading (underlined with =)",
222                                HeadingStyle::Setext2 => "Heading (underlined with -)",
223                                HeadingStyle::Consistent => "consistent style",
224                                HeadingStyle::SetextWithAtx => "setext-with-atx style",
225                                HeadingStyle::SetextWithAtxClosed => "setext-with-atx-closed style",
226                            }
227                        ),
228                        severity: Severity::Warning,
229                        fix,
230                    });
231                }
232            }
233        }
234
235        Ok(result)
236    }
237
238    fn fix(&self, ctx: &crate::lint_context::LintContext) -> Result<String, LintError> {
239        // Get all warnings with their fixes
240        let warnings = self.check(ctx)?;
241        let warnings =
242            crate::utils::fix_utils::filter_warnings_by_inline_config(warnings, ctx.inline_config(), self.name());
243
244        // If no warnings, return original content
245        if warnings.is_empty() {
246            return Ok(ctx.content.to_string());
247        }
248
249        // Collect all fixes and sort by range start (descending) to apply from end to beginning
250        let mut fixes: Vec<_> = warnings
251            .iter()
252            .filter_map(|w| w.fix.as_ref().map(|f| (f.range.start, f.range.end, &f.replacement)))
253            .collect();
254        fixes.sort_by(|a, b| b.0.cmp(&a.0));
255
256        // Apply fixes from end to beginning to preserve byte offsets
257        let mut result = ctx.content.to_string();
258        for (start, end, replacement) in fixes {
259            if start < result.len() && end <= result.len() && start <= end {
260                result.replace_range(start..end, replacement);
261            }
262        }
263
264        Ok(result)
265    }
266
267    fn category(&self) -> RuleCategory {
268        RuleCategory::Heading
269    }
270
271    fn should_skip(&self, ctx: &crate::lint_context::LintContext) -> bool {
272        // Fast path: check if document likely has headings using character frequency
273        if ctx.content.is_empty() || !ctx.likely_has_headings() {
274            return true;
275        }
276        // Verify headings actually exist (handles false positives from character frequency)
277        !ctx.lines.iter().any(|line| line.heading.is_some())
278    }
279
280    fn as_any(&self) -> &dyn std::any::Any {
281        self
282    }
283
284    fn default_config_section(&self) -> Option<(String, toml::Value)> {
285        let default_config = MD003Config::default();
286        let json_value = serde_json::to_value(&default_config).ok()?;
287        let toml_value = crate::rule_config_serde::json_to_toml_value(&json_value)?;
288
289        if let toml::Value::Table(table) = toml_value {
290            if !table.is_empty() {
291                Some((MD003Config::RULE_NAME.to_string(), toml::Value::Table(table)))
292            } else {
293                None
294            }
295        } else {
296            None
297        }
298    }
299
300    fn from_config(config: &crate::config::Config) -> Box<dyn Rule>
301    where
302        Self: Sized,
303    {
304        let rule_config = crate::rule_config_serde::load_rule_config::<MD003Config>(config);
305        Box::new(Self::from_config_struct(rule_config))
306    }
307}
308
309#[cfg(test)]
310mod tests {
311    use super::*;
312    use crate::lint_context::LintContext;
313
314    #[test]
315    fn test_atx_heading_style() {
316        let rule = MD003HeadingStyle::default();
317        let content = "# Heading 1\n## Heading 2\n### Heading 3";
318        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
319        let result = rule.check(&ctx).unwrap();
320        assert!(result.is_empty());
321    }
322
323    #[test]
324    fn test_setext_heading_style() {
325        let rule = MD003HeadingStyle::new(HeadingStyle::Setext1);
326        let content = "Heading 1\n=========\n\nHeading 2\n---------";
327        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
328        let result = rule.check(&ctx).unwrap();
329        assert!(result.is_empty());
330    }
331
332    #[test]
333    fn test_front_matter() {
334        let rule = MD003HeadingStyle::default();
335        let content = "---\ntitle: Test\n---\n\n# Heading 1\n## Heading 2";
336
337        // Test should detect headings and apply consistent style
338        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
339        let result = rule.check(&ctx).unwrap();
340        assert!(
341            result.is_empty(),
342            "No warnings expected for content with front matter, found: {result:?}"
343        );
344    }
345
346    #[test]
347    fn test_consistent_heading_style() {
348        // Default rule uses Atx which serves as our "consistent" mode
349        let rule = MD003HeadingStyle::default();
350        let content = "# Heading 1\n## Heading 2\n### Heading 3";
351        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
352        let result = rule.check(&ctx).unwrap();
353        assert!(result.is_empty());
354    }
355
356    #[test]
357    fn test_with_different_styles() {
358        // Test with consistent style (ATX)
359        let rule = MD003HeadingStyle::new(HeadingStyle::Consistent);
360        let content = "# Heading 1\n## Heading 2\n### Heading 3";
361        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
362        let result = rule.check(&ctx).unwrap();
363
364        // Make test more resilient
365        assert!(
366            result.is_empty(),
367            "No warnings expected for consistent ATX style, found: {result:?}"
368        );
369
370        // Test with incorrect style
371        let rule = MD003HeadingStyle::new(HeadingStyle::Atx);
372        let content = "# Heading 1 #\nHeading 2\n-----\n### Heading 3";
373        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
374        let result = rule.check(&ctx).unwrap();
375        assert!(
376            !result.is_empty(),
377            "Should have warnings for inconsistent heading styles"
378        );
379
380        // Test with setext style
381        let rule = MD003HeadingStyle::new(HeadingStyle::Setext1);
382        let content = "Heading 1\n=========\nHeading 2\n---------\n### Heading 3";
383        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
384        let result = rule.check(&ctx).unwrap();
385        // The level 3 heading can't be setext, so it's valid as ATX
386        assert!(
387            result.is_empty(),
388            "No warnings expected for setext style with ATX for level 3, found: {result:?}"
389        );
390    }
391
392    #[test]
393    fn test_setext_with_atx_style() {
394        let rule = MD003HeadingStyle::new(HeadingStyle::SetextWithAtx);
395        // Setext for h1/h2, ATX for h3-h6
396        let content = "Heading 1\n=========\n\nHeading 2\n---------\n\n### Heading 3\n\n#### Heading 4";
397        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
398        let result = rule.check(&ctx).unwrap();
399        assert!(
400            result.is_empty(),
401            "SesetxtWithAtx style should accept setext for h1/h2 and ATX for h3+"
402        );
403
404        // Test incorrect usage - ATX for h1/h2
405        let content_wrong = "# Heading 1\n## Heading 2\n### Heading 3";
406        let ctx_wrong = LintContext::new(content_wrong, crate::config::MarkdownFlavor::Standard, None);
407        let result_wrong = rule.check(&ctx_wrong).unwrap();
408        assert_eq!(
409            result_wrong.len(),
410            2,
411            "Should flag ATX headings for h1/h2 with setext_with_atx style"
412        );
413    }
414
415    #[test]
416    fn test_fix_preserves_attribute_lists() {
417        // ATX closed heading with attribute list, converted to ATX
418        let rule = MD003HeadingStyle::new(HeadingStyle::Atx);
419        let content = "# Heading { #custom-id .class } #";
420        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
421
422        // Should flag: found ATX closed, expected ATX
423        let warnings = rule.check(&ctx).unwrap();
424        assert_eq!(warnings.len(), 1);
425        let fix = warnings[0].fix.as_ref().expect("Should have a fix");
426        assert!(
427            fix.replacement.contains("{ #custom-id .class }"),
428            "check() fix should preserve attribute list, got: {}",
429            fix.replacement
430        );
431
432        // Verify fix() also preserves attribute list
433        let fixed = rule.fix(&ctx).unwrap();
434        assert!(
435            fixed.contains("{ #custom-id .class }"),
436            "fix() should preserve attribute list, got: {fixed}"
437        );
438        assert!(
439            !fixed.contains(" #\n") && !fixed.ends_with(" #"),
440            "fix() should remove ATX closed trailing hashes, got: {fixed}"
441        );
442    }
443
444    #[test]
445    fn test_setext_with_atx_closed_style() {
446        let rule = MD003HeadingStyle::new(HeadingStyle::SetextWithAtxClosed);
447        // Setext for h1/h2, ATX closed for h3-h6
448        let content = "Heading 1\n=========\n\nHeading 2\n---------\n\n### Heading 3 ###\n\n#### Heading 4 ####";
449        let ctx = LintContext::new(content, crate::config::MarkdownFlavor::Standard, None);
450        let result = rule.check(&ctx).unwrap();
451        assert!(
452            result.is_empty(),
453            "SetextWithAtxClosed style should accept setext for h1/h2 and ATX closed for h3+"
454        );
455
456        // Test incorrect usage - regular ATX for h3+
457        let content_wrong = "Heading 1\n=========\n\n### Heading 3\n\n#### Heading 4";
458        let ctx_wrong = LintContext::new(content_wrong, crate::config::MarkdownFlavor::Standard, None);
459        let result_wrong = rule.check(&ctx_wrong).unwrap();
460        assert_eq!(
461            result_wrong.len(),
462            2,
463            "Should flag non-closed ATX headings for h3+ with setext_with_atx_closed style"
464        );
465    }
466}
rumdl_lib/rules/md003_heading_style.rs

rumdl_lib/rules/
md003_heading_style.rs
