Some minor fixes: (#10)

- plug  md003 to the linter
- more detailed messages for rules violations
- documentation for md003

README.md

@@ -45,4 +45,4 @@ TBD
 ## Rules
 
 - **[MD001](docs/rules/md001.md)** *heading-increment* - Heading levels should only increment by one level at a time
-
+- **[MD003](docs/rules/md003.md)** *heading-style* - Heading style

docs/rules/md003.md

@@ -0,0 +1,37 @@
+# `MD003` - Heading style
+
+Tags: `headings`
+
+Aliases: `heading-style`
+
+Parameters:
+
+- `style`: Heading style (`string`, default `consistent`, values `atx` / `consistent` / `setext`)
+
+This rule is triggered when different heading styles are used in the same
+document:
+
+```markdown
+# ATX style H1
+
+Setext style H1
+===============
+```
+
+To fix the issue, use consistent heading styles throughout the document:
+
+```markdown
+# ATX style H1
+
+## ATX style H2
+```
+
+Note: The placement of a horizontal rule directly below a line of text can
+trigger this rule by turning that text into a level 2 setext-style heading:
+
+```markdown
+A line of text followed by a horizontal rule becomes a heading
+---
+```
+
+Rationale: Consistent formatting makes it easier to understand a document.

src/linter.rs

@@ -43,13 +43,14 @@ pub struct RuleViolation {
 impl RuleViolation {
     pub fn new(
         rule: &'static Rule,
+        message: String,
         severity: RuleViolationSeverity,
         file_path: PathBuf,
         pos: &Sourcepos,
     ) -> Self {
         Self {
             rule,
-            message: rule.description.to_string(),
+            message,
             severity,
             location: Location {
                 file_path,

src/main.rs

@@ -18,7 +18,10 @@ fn main() -> anyhow::Result<()> {
     let file_content = fs::read_to_string(&file_path)
         .context(format!("Can't read file {}", &file_path.to_string_lossy()))?;
 
-    let rules = vec![quickmark::rules::md001::MD001];
+    let rules = vec![
+        quickmark::rules::md001::MD001,
+        quickmark::rules::md003::MD003,
+    ];
 
     let context = quickmark::linter::Context {
         file_path: file_path.clone(),
@@ -33,14 +36,14 @@ fn main() -> anyhow::Result<()> {
         .lint(&file_content)
         .iter()
         .fold((0, 0), |(warns, errs), v| {
-            eprint!("{}", v);
+            eprintln!("{}", v);
             match &v.severity {
                 Error => (warns, errs + 1),
                 _ => (warns + 1, errs),
             }
         });
 
-    println!("\n\nErrors: {}", errs);
+    println!("\nErrors: {}", errs);
     println!("Warnings: {}", warns);
 
     let exit_code = min(errs, 1);

src/rules/md001.rs

@@ -25,6 +25,12 @@ impl RuleLinter for MD001Linter {
             {
                 return Option::Some(RuleViolation::new(
                     &MD001,
+                    format!(
+                        "{} [Expected: h{}; Actual: h{}]",
+                        MD001.description,
+                        self.current_heading_level + 1,
+                        level
+                    ),
                     RuleViolationSeverity::Error,
                     self.context.file_path.clone(),
                     &(node.sourcepos),

src/rules/md003.rs

@@ -1,3 +1,5 @@
+use core::fmt;
+
 use comrak::nodes::{Ast, NodeHeading, NodeValue};
 
 use crate::linter::{Context, HeadingStyle, RuleLinter, RuleViolation, RuleViolationSeverity};
@@ -10,6 +12,15 @@ enum Style {
     Atx,
 }
 
+impl fmt::Display for Style {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Style::Setext => write!(f, "setext"),
+            Style::Atx => write!(f, "atx"),
+        }
+    }
+}
+
 pub(crate) struct MD003Linter {
     context: Context,
     enforced_style: Option<Style>,
@@ -44,6 +55,10 @@ impl RuleLinter for MD003Linter {
                 if style != *enforced_style {
                     return Option::Some(RuleViolation::new(
                         &MD003,
+                        format!(
+                            "{} [Expected: {}; Actual: {}]",
+                            MD003.description, enforced_style, style
+                        ),
                         RuleViolationSeverity::Error,
                         self.context.file_path.clone(),
                         &node.sourcepos,
@@ -84,7 +99,8 @@ mod test {
         };
         let mut linter = (MD003.new_linter)(context);
 
-        let input = "Setext level 1
+        let input = "
+Setext level 1
 --------------
 Setext level 2
 ==============
@@ -105,7 +121,8 @@ Setext level 2
         };
         let mut linter = (MD003.new_linter)(context);
 
-        let input = "Setext level 1
+        let input = "
+Setext level 1
 --------------
 Setext level 2
 ==============
@@ -124,9 +141,94 @@ Setext level 2
         };
         let mut linter = (MD003.new_linter)(context);
 
-        let input = "# Atx heading 1
+        let input = "
+# Atx heading 1
 ## Atx heading 2
 ### Atx heading 3
+";
+        let violations = lint_content(input, &mut linter);
+        assert_eq!(violations.len(), 0);
+    }
+
+    #[test]
+    fn test_heading_style_atx_positive() {
+        let context = Context {
+            file_path: PathBuf::from("test.md"),
+            settings: Settings {
+                heading_style: HeadingStyle::Atx,
+            },
+        };
+        let mut linter = (MD003.new_linter)(context);
+
+        let input = "
+Setext heading 1
+----------------
+Setext heading 2
+================
+### Atx heading 3
+";
+        let violations = lint_content(input, &mut linter);
+        assert_eq!(violations.len(), 2);
+    }
+
+    #[test]
+    fn test_heading_style_atx_negative() {
+        let context = Context {
+            file_path: PathBuf::from("test.md"),
+            settings: Settings {
+                heading_style: HeadingStyle::Atx,
+            },
+        };
+        let mut linter = (MD003.new_linter)(context);
+
+        let input = "
+# Atx heading 1
+## Atx heading 2
+### Atx heading 3
+";
+        let violations = lint_content(input, &mut linter);
+        assert_eq!(violations.len(), 0);
+    }
+
+    #[test]
+    fn test_heading_style_setext_positive() {
+        let context = Context {
+            file_path: PathBuf::from("test.md"),
+            settings: Settings {
+                heading_style: HeadingStyle::Setext,
+            },
+        };
+        let mut linter = (MD003.new_linter)(context);
+
+        let input = "
+# Atx heading 1
+Setext heading 1
+----------------
+Setext heading 2
+================
+### Atx heading 3
+";
+        let violations = lint_content(input, &mut linter);
+        assert_eq!(violations.len(), 2);
+    }
+
+    #[test]
+    fn test_heading_style_setext_negative() {
+        let context = Context {
+            file_path: PathBuf::from("test.md"),
+            settings: Settings {
+                heading_style: HeadingStyle::Setext,
+            },
+        };
+        let mut linter = (MD003.new_linter)(context);
+
+        let input = "
+Setext heading 1
+----------------
+Setext heading 2
+================
+Setext heading 2
+================
 ";
         let violations = lint_content(input, &mut linter);
         assert_eq!(violations.len(), 0);