Update MD029/ol-prefix to treat 0/1/2 as "ordered" (fixes #250).

doc/Rules.md

@@ -945,8 +945,8 @@ Parameters: style ("one", "ordered", "one_or_ordered", "zero"; default "one_or_o
 
 This rule is triggered for ordered lists that do not either start with '1.' or
 do not have a prefix that increases in numerical order (depending on the
-configured style). The less-common pattern of using '0.' for all prefixes is
-also supported.
+configured style). The less-common patterns of using '0.' as a first prefix or
+for all prefixes is also supported.
 
 Example valid list if the style is configured as 'one':
 
@@ -956,7 +956,7 @@ Example valid list if the style is configured as 'one':
 1. Done.
 ```
 
-Example valid list if the style is configured as 'ordered':
+Examples of valid lists if the style is configured as 'ordered':
 
 ```markdown
 1. Do this.
@@ -964,7 +964,13 @@ Example valid list if the style is configured as 'ordered':
 3. Done.
 ```
 
-Both examples are valid when the style is configured as 'one_or_ordered'.
+```markdown
+0. Do this.
+1. Do that.
+2. Done.
+```
+
+All three examples are valid when the style is configured as 'one_or_ordered'.
 
 Example valid list if the style is configured as 'zero':
 

lib/md029.js

@@ -18,26 +18,47 @@ module.exports = {
   "tags": [ "ol" ],
   "function": function MD029(params, onError) {
     const style = String(params.config.style || "one_or_ordered");
-    flattenedLists().forEach((list) => {
-      if (!list.unordered) {
+    flattenedLists().filter((list) => !list.unordered).forEach((list) => {
+      const { items } = list;
+      let current = 1;
+      let incrementing = false;
+      // Check for incrementing number pattern 1/2/3 or 0/1/2
+      if (items.length >= 2) {
+        const first = orderedListItemMarkerRe.exec(items[0].line);
+        const second = orderedListItemMarkerRe.exec(items[1].line);
+        if (first && second) {
+          const [ , firstNumber ] = first;
+          const [ , secondNumber ] = second;
+          if ((secondNumber !== "1") || (firstNumber === "0")) {
+            incrementing = true;
+            if (firstNumber === "0") {
+              current = 0;
+            }
+          }
+        }
+      }
+      // Determine effective style
       let listStyle = style;
       if (listStyle === "one_or_ordered") {
-          const second = (list.items.length > 1) &&
-            orderedListItemMarkerRe.exec(list.items[1].line);
-          listStyle = (second && (second[1] !== "1")) ? "ordered" : "one";
+        listStyle = incrementing ? "ordered" : "one";
       }
-        let number = (listStyle === "zero") ? 0 : 1;
-        list.items.forEach((item) => {
+      // Force expected value for 0/0/0 and 1/1/1 patterns
+      if (listStyle === "zero") {
+        current = 0;
+      } else if (listStyle === "one") {
+        current = 1;
+      }
+      // Validate each list item marker
+      items.forEach((item) => {
         const match = orderedListItemMarkerRe.exec(item.line);
         addErrorDetailIf(onError, item.lineNumber,
-            String(number), !match || match[1],
+          String(current), !match || match[1],
           "Style: " + listStyleExamples[listStyle], null,
           rangeFromRegExp(item.line, listItemMarkerRe));
         if (listStyle === "ordered") {
-            number++;
+          current++;
         }
       });
-      }
     });
   }
 };

test/ordered-list-item-prefix-one.md

@@ -60,3 +60,15 @@ text
   2. Item {MD029}
   4. Item {MD029}
 - Item
+
+text
+
+0. Item {MD029}
+1. Item
+2. Item {MD029}
+
+text
+
+0. Item {MD029}
+1. Item
+3. Item {MD029}

test/ordered-list-item-prefix-one_or_ordered.md

@@ -60,3 +60,15 @@ text
   2. Item
   4. Item {MD029}
 - Item
+
+text
+
+0. Item
+1. Item
+2. Item
+
+text
+
+0. Item
+1. Item
+3. Item {MD029}

test/ordered-list-item-prefix-ordered.md

@@ -60,3 +60,15 @@ text
   2. Item
   4. Item {MD029}
 - Item
+
+text
+
+0. Item
+1. Item
+2. Item
+
+text
+
+0. Item
+1. Item
+3. Item {MD029}

test/ordered-list-item-prefix-zero.md

@@ -60,3 +60,15 @@ text
   1. Item {MD029}
   2. Item {MD029}
 - Item
+
+text
+
+0. Item
+1. Item {MD029}
+2. Item {MD029}
+
+text
+
+0. Item
+1. Item {MD029}
+3. Item {MD029}