Generalise markdownlint directive detection

src/wrap.rs

@@ -18,6 +18,22 @@ static FOOTNOTE_RE: std::sync::LazyLock<Regex> =
 static BLOCKQUOTE_RE: std::sync::LazyLock<Regex> =
     std::sync::LazyLock::new(|| Regex::new(r"^(\s*(?:>\s*)+)(.*)$").unwrap());
 
+/// Matches `markdownlint` comment directives.
+///
+/// The regex is case-insensitive and recognises these forms with optional rule
+/// names (including plugin rules such as `MD013/line-length` or
+/// `plugin/rule-name`):
+/// - `<!-- markdownlint-disable -->`
+/// - `<!-- markdownlint-enable -->`
+/// - `<!-- markdownlint-disable-line MD001 MD005 -->`
+/// - `<!-- markdownlint-disable-next-line MD001 MD005 -->`
+static MARKDOWNLINT_DIRECTIVE_RE: std::sync::LazyLock<Regex> = std::sync::LazyLock::new(|| {
+    Regex::new(
+        r"(?i)^\s*<!--\s*markdownlint-(?:disable|enable|disable-line|disable-next-line)(?:\s+[A-Za-z0-9_\-/]+)*\s*-->\s*$",
+    )
+    .expect("valid markdownlint regex")
+});
+
 struct PrefixHandler {
     re: &'static std::sync::LazyLock<Regex>,
     is_bq: bool,
@@ -306,6 +322,10 @@ fn wrap_preserving_code(text: &str, width: usize) -> Vec<String> {
 #[doc(hidden)]
 pub fn is_fence(line: &str) -> bool { FENCE_RE.is_match(line) }
 
+pub(crate) fn is_markdownlint_directive(line: &str) -> bool {
+    MARKDOWNLINT_DIRECTIVE_RE.is_match(line)
+}
+
 fn flush_paragraph(out: &mut Vec<String>, buf: &[(String, bool)], indent: &str, width: usize) {
     if buf.is_empty() {
         return;
@@ -421,6 +441,14 @@ pub fn wrap_text(lines: &[String], width: usize) -> Vec<String> {
             continue;
         }
 
+        if is_markdownlint_directive(line) {
+            flush_paragraph(&mut out, &buf, &indent, width);
+            buf.clear();
+            indent.clear();
+            out.push(line.clone());
+            continue;
+        }
+
         if line.trim().is_empty() {
             flush_paragraph(&mut out, &buf, &indent, width);
             buf.clear();

tests/markdownlint.rs

@@ -0,0 +1,117 @@
+//! Tests for markdownlint directive handling during wrapping.
+//!
+//! These tests ensure that comment directives such as
+//! `<!-- markdownlint-disable-next-line -->` remain on their own line
+//! after processing. Regular comments should still be wrapped normally.
+
+use mdtablefix::process_stream;
+
+#[macro_use]
+mod prelude;
+use prelude::*;
+
+/// The disable-next-line directive must remain intact after wrapping.
+#[test]
+fn test_markdownlint_disable_next_line_preserved() {
+    let input = lines_vec![
+        "[roadmap](./roadmap.md) and expands on the design ideas described in",
+        "<!--  markdownlint-disable-next-line  MD013  -->",
+    ];
+    let output = process_stream(&input);
+    assert_eq!(output, input);
+}
+
+/// The disable-next-line directive must remain intact when in the middle of the input.
+#[test]
+fn test_markdownlint_disable_next_line_preserved_middle() {
+    let input = lines_vec![
+        "This is the first line.",
+        "<!--  markdownlint-disable-next-line  MD013  -->",
+        "This is the third line.",
+    ];
+    let output = process_stream(&input);
+    assert_eq!(output, input);
+}
+
+/// Regular comments should still wrap when necessary.
+#[test]
+fn test_regular_comment_wraps_normally() {
+    let input = lines_vec![
+        "Intro text that preludes a lengthy comment.",
+        concat!(
+            "<!-- This comment contains many words and should be wrapped across ",
+            "multiple lines to ensure that regular comments are formatted ",
+            "correctly. -->"
+        ),
+    ];
+    let output = process_stream(&input);
+    assert_eq!(
+        output,
+        lines_vec![
+            "Intro text that preludes a lengthy comment. <!-- This comment contains many",
+            "words and should be wrapped across multiple lines to ensure that regular",
+            "comments are formatted correctly. -->",
+        ]
+    );
+}
+
+/// Other markdownlint directives should also remain on their own lines, even
+/// when indented or combined with multiple rule names.
+#[rstest]
+#[case("<!-- markdownlint-disable-line MD001 MD005 -->")]
+#[case("<!-- markdownlint-enable MD001 -->")]
+#[case("    <!-- markdownlint-disable -->")]
+#[case("<!--  markdownlint-disable   MD001   MD002  -->")]
+#[case("<!-- MarkDownLint-disable-line MD003 -->")]
+#[case("<!-- MARKDOWNLINT-disable-next-line MD004 MD005 -->")]
+fn test_markdownlint_directive_variants_preserved(#[case] directive: &str) {
+    let input = lines_vec!["A preceding line.", directive];
+    let output = process_stream(&input);
+    assert_eq!(output, input);
+}
+
+/// Comments that resemble directives but are invalid should wrap normally.
+#[test]
+fn test_non_directive_comment_wraps() {
+    let input = lines_vec!["Intro line.", "<!-- markdowndisable -->"];
+    let output = process_stream(&input);
+    assert_eq!(output, lines_vec!["Intro line. <!-- markdowndisable -->"]);
+}
+
+/// Malformed or partially correct directive comments should wrap normally.
+#[test]
+fn test_malformed_directive_missing_closing() {
+    let input = lines_vec!["Text before.", "<!-- markdownlint-disable"];
+    let output = process_stream(&input);
+    assert_eq!(output, lines_vec!["Text before. <!-- markdownlint-disable"]);
+}
+
+#[test]
+fn test_malformed_directive_extra_text() {
+    let input = lines_vec!["Text before.", "<!-- markdownlint-disable --> extra"];
+    let output = process_stream(&input);
+    assert_eq!(
+        output,
+        lines_vec!["Text before. <!-- markdownlint-disable --> extra"]
+    );
+}
+
+#[test]
+fn test_malformed_directive_typo() {
+    let input = lines_vec!["Text before.", "<!-- markdownlnt-disable-line MD001 -->"];
+    let output = process_stream(&input);
+    assert_eq!(
+        output,
+        lines_vec!["Text before. <!-- markdownlnt-disable-line MD001 -->"]
+    );
+}
+
+#[test]
+fn test_malformed_directive_incomplete_tag() {
+    let input = lines_vec!["Text before.", "<!-- markdownlint-disable-line MD001 "];
+    let output = process_stream(&input);
+    assert_eq!(
+        output,
+        lines_vec!["Text before. <!-- markdownlint-disable-line MD001"]
+    );
+}