Update MD024/no-duplicate-heading to allow non-sibling duplicates (fixes #136).

doc/Rules.md

@@ -1,3 +1,4 @@
+
 # Rules
 
 This document contains a description of all rules, what they are checking for,
@@ -681,6 +682,8 @@ Tags: headings, headers
 
 Aliases: no-duplicate-heading, no-duplicate-header
 
+Parameters: siblings_only, allow_different_nesting (boolean; default `false`)
+
 This rule is triggered if there are multiple headings in the document that have
 the same text:
 
@@ -702,6 +705,22 @@ Rationale: Some markdown parses generate anchors for headings based on the
 heading name, and having headings with the same content can cause problems with
 this.
 
+If the parameter `siblings_only` (alternatively `allow_different_nesting`) is
+set to `true`, heading duplication is allowed for non-sibling headings (common
+in change logs):
+
+```markdown
+# Change log
+
+## 1.0.0
+
+### Features
+
+## 2.0.0
+
+### Features
+```
+
 <a name="md025"></a>
 
 ## MD025 - Multiple top level headings in the same document

lib/md024.js

@@ -9,8 +9,24 @@ module.exports = {
   "description": "Multiple headings with the same content",
   "tags": [ "headings", "headers" ],
   "function": function MD024(params, onError) {
-    const knownContent = [];
+    const siblingsOnly = params.config.siblings_only ||
+      params.config.allow_different_nesting || false;
+    const knownContents = [ null, [] ];
+    let lastLevel = 1;
+    let knownContent = knownContents[lastLevel];
     shared.forEachHeading(params, function forHeading(heading, content) {
+      if (siblingsOnly) {
+        const newLevel = heading.tag.slice(1);
+        while (lastLevel < newLevel) {
+          lastLevel++;
+          knownContents[lastLevel] = [];
+        }
+        while (lastLevel > newLevel) {
+          knownContents[lastLevel] = [];
+          lastLevel--;
+        }
+        knownContent = knownContents[newLevel];
+      }
       if (knownContent.indexOf(content) === -1) {
         knownContent.push(content);
       } else {

schema/build-config-schema.js

@@ -25,6 +25,7 @@ const schema = {
 const tags = {};
 
 // Add rules
+// eslint-disable-next-line complexity
 rules.forEach(function forRule(rule) {
   rule.tags.forEach(function forTag(tag) {
     const tagRules = tags[tag] || [];
@@ -151,6 +152,20 @@ rules.forEach(function forRule(rule) {
         }
       };
       break;
+    case "MD024":
+      scheme.properties = {
+        "allow_different_nesting": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        },
+        "siblings_only": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        }
+      };
+      break;
     case "MD026":
     case "MD036":
       scheme.properties = {

schema/markdownlint-config-schema.json

@@ -515,18 +515,66 @@
     },
     "MD024": {
       "description": "MD024/no-duplicate-heading/no-duplicate-header - Multiple headings with the same content",
-      "type": "boolean",
+      "type": [
-      "default": true
+        "boolean",
+        "object"
+      ],
+      "default": true,
+      "properties": {
+        "allow_different_nesting": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        },
+        "siblings_only": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        }
+      },
+      "additionalProperties": false
     },
     "no-duplicate-heading": {
       "description": "MD024/no-duplicate-heading/no-duplicate-header - Multiple headings with the same content",
-      "type": "boolean",
+      "type": [
-      "default": true
+        "boolean",
+        "object"
+      ],
+      "default": true,
+      "properties": {
+        "allow_different_nesting": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        },
+        "siblings_only": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        }
+      },
+      "additionalProperties": false
     },
     "no-duplicate-header": {
       "description": "MD024/no-duplicate-heading/no-duplicate-header - Multiple headings with the same content",
-      "type": "boolean",
+      "type": [
-      "default": true
+        "boolean",
+        "object"
+      ],
+      "default": true,
+      "properties": {
+        "allow_different_nesting": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        },
+        "siblings_only": {
+          "description": "Only check sibling headings",
+          "type": "boolean",
+          "default": false
+        }
+      },
+      "additionalProperties": false
     },
     "MD025": {
       "description": "MD025/single-h1 - Multiple top level headings in the same document",

test/heading-duplicate-content-siblings-only.json

@@ -0,0 +1,7 @@
+{
+  "default": true,
+  "MD003": false,
+  "MD024": {
+    "siblings_only": true
+  }
+}

test/heading-duplicate-content-siblings-only.md

@@ -0,0 +1,96 @@
+# Heading duplicate content siblings only
+
+# A
+
+{MD025:3}
+
+## B
+
+### C
+
+## B
+
+{MD024:11}
+
+### C
+
+## D
+
+### C
+
+### E
+
+### C
+
+{MD024:23}
+
+##### F
+
+{MD001:27}
+
+#### G
+
+##### F
+
+#### G
+
+{MD024:35}
+
+### E
+
+{MD024:39}
+
+# A
+
+{MD024:43} {MD025:43}
+
+## B
+
+### C
+
+## B
+
+{MD024:51}
+
+# Heading duplicate content siblings only
+
+{MD024:55} {MD025:55}
+
+AA
+==
+
+{MD025:59}
+
+AA
+--
+
+BB
+--
+
+CC
+--
+
+BB
+--
+
+{MD024:73}
+
+BB
+==
+
+{MD025:78}
+
+BB
+--
+
+## AAA ##
+
+### BBB ###
+
+## BBB ##
+
+### BBB ###
+
+## BBB ##
+
+{MD024:94}

test/heading_duplicate_content_different_nesting.json

@@ -0,0 +1,6 @@
+{
+  "default": true,
+  "MD024": {
+    "allow_different_nesting": true
+  }
+}

test/heading_duplicate_content_different_nesting.md

@@ -0,0 +1,11 @@
+# Change log
+
+## 2.0.0
+
+### Bug fixes
+
+### Features
+
+## 1.0.0
+
+### Bug fixes

test/heading_duplicate_content_no_different_nesting.md

@@ -0,0 +1,13 @@
+# Change log
+
+## 2.0.0
+
+### Bug fixes
+
+### Features
+
+## 1.0.0
+
+### Bug fixes
+
+{MD024:11}

test/markdownlint-test.js

@@ -1117,7 +1117,7 @@ module.exports.readme = function readme(test) {
 };
 
 module.exports.doc = function doc(test) {
-  test.expect(310);
+  test.expect(311);
   fs.readFile("doc/Rules.md", shared.utf8Encoding,
     function readFile(err, contents) {
       test.ifError(err);
@@ -1131,11 +1131,11 @@ module.exports.doc = function doc(test) {
       function testTagsAliasesParams(r) {
         r = r || "[NO RULE]";
         test.ok(ruleHasTags,
-          "Missing tags for rule " + r.toString() + ".");
+          "Missing tags for rule " + r.names + ".");
         test.ok(ruleHasAliases,
-          "Missing aliases for rule " + r.toString() + ".");
+          "Missing aliases for rule " + r.names + ".");
         test.ok(!ruleUsesParams,
-          "Missing parameters for rule " + r.toString() + ".");
+          "Missing parameters for rule " + r.names + ".");
       }
       md.parse(contents, {}).forEach(function forToken(token) {
         if ((token.type === "heading_open") && (token.tag === "h2")) {
@@ -1161,12 +1161,12 @@ module.exports.doc = function doc(test) {
             }
           } else if (/^Tags: /.test(token.content) && rule) {
             test.deepEqual(token.content.split(tagAliasParameterRe).slice(1),
-              rule.tags, "Tag mismatch for rule " + rule.toString() + ".");
+              rule.tags, "Tag mismatch for rule " + rule.names + ".");
             ruleHasTags = true;
           } else if (/^Aliases: /.test(token.content) && rule) {
             test.deepEqual(token.content.split(tagAliasParameterRe).slice(1),
               rule.names.slice(1),
-              "Alias mismatch for rule " + rule.toString() + ".");
+              "Alias mismatch for rule " + rule.names + ".");
             ruleHasAliases = true;
           } else if (/^Parameters: /.test(token.content) && rule) {
             let inDetails = false;
@@ -1177,7 +1177,7 @@ module.exports.doc = function doc(test) {
                 return !inDetails;
               });
             test.deepEqual(parameters, ruleUsesParams,
-              "Missing parameter for rule " + rule.toString());
+              "Missing parameter for rule " + rule.names);
             ruleUsesParams = null;
           }
         }
@@ -1185,7 +1185,7 @@ module.exports.doc = function doc(test) {
       const ruleLeft = rulesLeft.shift();
       test.ok(!ruleLeft,
         "Missing rule documentation for " +
-          (ruleLeft || "[NO RULE]").toString() + ".");
+          (ruleLeft || { "names": "[NO RULE]" }).names + ".");
       if (rule) {
         testTagsAliasesParams(rule);
       }