Add headers parameter to MD013/line-length (fixes #35).

doc/Rules.md

@@ -334,7 +334,7 @@ Tags: line_length
 
 Aliases: line-length
 
-Parameters: line_length, code_blocks, tables (number; default 80, boolean; default true)
+Parameters: line_length, code_blocks, tables, headers (number; default 80, boolean; default true)
 
 This rule is triggered when there are lines that are longer than the
 configured line length (default: 80 characters). To fix this, split the line
@@ -344,8 +344,8 @@ This rule has an exception where there is no whitespace beyond the configured
 line length. This allows you to still include items such as long URLs without
 being forced to break them in the middle.
 
-You also have the option to exclude this rule for code blocks and tables. To
-do this, set the `code_blocks` and/or `tables` parameters to false.
+You have the option to exclude this rule for code blocks, tables, or headers.
+To do so, set the `code_blocks`, `tables`, or `headers` parameter(s) to false.
 
 Code blocks are included in this rule by default since it is often a
 requirement for document readability, and tentatively compatible with code

lib/rules.js

@@ -427,13 +427,23 @@ module.exports = [
       var includeCodeBlocks = (codeBlocks === undefined) ? true : !!codeBlocks;
       var tables = params.options.tables;
       var includeTables = (tables === undefined) ? true : !!tables;
+      var headers = params.options.headers;
+      var includeHeaders = (headers === undefined) ? true : !!headers;
+      var headerLineNumbers = [];
+      if (!includeHeaders) {
+        forEachHeading(params, function forHeading(heading) {
+          headerLineNumbers.push(heading.lineNumber);
+        });
+      }
       var re = longLineReFunc(params.options);
       forEachLine(params,
         function forLine(line, lineIndex, inCode, onFence, inTable) {
+          var lineNumber = lineIndex + 1;
           if ((includeCodeBlocks || !inCode) &&
               (includeTables || !inTable) &&
+              (includeHeaders || (headerLineNumbers.indexOf(lineNumber)) < 0) &&
               re.test(line)) {
-            errors.addDetailIf(lineIndex + 1, lineLength, line.length);
+            errors.addDetailIf(lineNumber, lineLength, line.length);
           }
         });
     }

schema/build-config-schema.js

@@ -129,6 +129,11 @@ rules.forEach(function forRule(rule) {
           "description": "Include tables",
           "type": "boolean",
           "default": true
+        },
+        "headers": {
+          "description": "Include headers",
+          "type": "boolean",
+          "default": true
         }
       };
       break;

schema/markdownlint-config-schema.json

@@ -323,6 +323,11 @@
           "description": "Include tables",
           "type": "boolean",
           "default": true
+        },
+        "headers": {
+          "description": "Include headers",
+          "type": "boolean",
+          "default": true
         }
       },
       "additionalProperties": false
@@ -349,6 +354,11 @@
           "description": "Include tables",
           "type": "boolean",
           "default": true
+        },
+        "headers": {
+          "description": "Include headers",
+          "type": "boolean",
+          "default": true
         }
       },
       "additionalProperties": false

test/long-header-exceptions.json

@@ -0,0 +1,6 @@
+{
+  "default": true,
+  "MD013": {
+    "headers": false
+  }
+}

test/long-header-exceptions.md

@@ -0,0 +1,21 @@
+# Header
+
+Text
+
+## Header header header header header header header header header header header header header header header header
+
+Text
+
+Text text text text text text text text text text text text text text text text text text text text text text text text {MD013}
+
+## Header header
+
+Text
+
+Text text text text text text text text text text text text text text text text text text text text text text text text {MD013}
+
+### Header header header header header header header header header header header header header header header header header
+
+Text
+
+Text text text text text text text text text text text text text text text text text text text text text text text text {MD013}