Add style "zero" to MD029/ol-prefix (fixes #140).

doc/Rules.md

@@ -863,11 +863,12 @@ Tags: ol
 
 Aliases: ol-prefix
 
-Parameters: style ("one", "ordered", "one_or_ordered"; default "one_or_ordered")
+Parameters: style ("one", "ordered", "one_or_ordered", "zero"; default "one_or_ordered")
 
-This rule is triggered on ordered lists that do not either start with '1.' or
+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).
+configured style). The less-common pattern of using '0.' for all prefixes is
+also supported.
 
 Example valid list if the style is configured as 'one':
 
@@ -887,6 +888,14 @@ Example valid list if the style is configured as 'ordered':
 
 Both examples are valid when the style is configured as 'one_or_ordered'.
 
+Example valid list if the style is configured as 'zero':
+
+```markdown
+0. Do this.
+0. Do that.
+0. Done.
+```
+
 Example invalid list for all styles:
 
 ```markdown

lib/md029.js

@@ -4,6 +4,12 @@
 
 const shared = require("./shared");
 
+const listStyleExamples = {
+  "one": "1/1/1",
+  "ordered": "1/2/3",
+  "zero": "0/0/0"
+};
+
 module.exports = {
   "names": [ "MD029", "ol-prefix" ],
   "description": "Ordered list item prefix",
@@ -18,12 +24,12 @@ module.exports = {
             shared.orderedListItemMarkerRe.exec(list.items[1].line);
           listStyle = (second && (second[1] !== "1")) ? "ordered" : "one";
         }
-        let number = 1;
+        let number = (listStyle === "zero") ? 0 : 1;
         list.items.forEach(function forItem(item) {
           const match = shared.orderedListItemMarkerRe.exec(item.line);
           shared.addErrorDetailIf(onError, item.lineNumber,
             String(number), !match || match[1],
-            "Style: " + (listStyle === "one" ? "1/1/1" : "1/2/3"),
+            "Style: " + listStyleExamples[listStyle],
             shared.rangeFromRegExp(item.line, shared.listItemMarkerRe));
           if (listStyle === "ordered") {
             number++;

schema/build-config-schema.js

@@ -184,7 +184,8 @@ rules.forEach(function forRule(rule) {
           "enum": [
             "one",
             "ordered",
-            "one_or_ordered"
+            "one_or_ordered",
+            "zero"
           ],
           "default": "one_or_ordered"
         }

schema/markdownlint-config-schema.json

@@ -674,7 +674,8 @@
           "enum": [
             "one",
             "ordered",
-            "one_or_ordered"
+            "one_or_ordered",
+            "zero"
           ],
           "default": "one_or_ordered"
         }
@@ -695,7 +696,8 @@
           "enum": [
             "one",
             "ordered",
-            "one_or_ordered"
+            "one_or_ordered",
+            "zero"
           ],
           "default": "one_or_ordered"
         }

test/detailed-results-ordered-list-item-prefix-single.md

@@ -0,0 +1,3 @@
+# Ordered list examples
+
+9. Item

test/detailed-results-ordered-list-item-prefix-single.results.json

@@ -0,0 +1,11 @@
+[
+    {
+        "lineNumber": 3,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 1; Actual: 9; Style: 1/1/1",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    }
+]

test/detailed-results-ordered-list-item-prefix-zero.json

@@ -0,0 +1,6 @@
+{
+  "default": true,
+  "MD029": {
+    "style": "zero"
+  }
+}

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

@@ -0,0 +1,19 @@
+# Ordered list examples
+
+text
+
+0. Item
+0. Item
+0. Item
+
+text
+
+1. Item
+1. Item
+1. Item
+
+text
+
+1. Item
+2. Item
+3. Item

test/detailed-results-ordered-list-item-prefix-zero.results.json

@@ -0,0 +1,56 @@
+[
+    {
+        "lineNumber": 11,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 0; Actual: 1; Style: 0/0/0",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    },
+    {
+        "lineNumber": 12,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 0; Actual: 1; Style: 0/0/0",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    },
+    {
+        "lineNumber": 13,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 0; Actual: 1; Style: 0/0/0",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    },
+    {
+        "lineNumber": 17,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 0; Actual: 1; Style: 0/0/0",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    },
+    {
+        "lineNumber": 18,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 0; Actual: 2; Style: 0/0/0",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    },
+    {
+        "lineNumber": 19,
+        "ruleNames": [ "MD029", "ol-prefix" ],
+        "ruleDescription": "Ordered list item prefix",
+        "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md029",
+        "errorDetail": "Expected: 0; Actual: 3; Style: 0/0/0",
+        "errorContext": null,
+        "errorRange": [1, 3]
+    }
+]

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

@@ -0,0 +1,6 @@
+{
+  "default": true,
+  "MD029": {
+    "style": "zero"
+  }
+}

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

@@ -0,0 +1,62 @@
+# Ordered list examples
+
+text
+
+0. Item
+
+text
+
+1. Item {MD029}
+
+text
+
+0. Item
+0. Item
+0. Item
+
+text
+
+1. Item {MD029}
+2. Item {MD029}
+3. Item {MD029}
+
+text
+
+0. Item
+1. Item {MD029}
+0. Item
+2. Item {MD029}
+
+text
+
+0. Item
+0. Item
+2. Item {MD029}
+0. Item
+
+text
+
+1. Item {MD029}
+2. Item {MD029}
+3. Item {MD029}
+
+text
+
+4. Item {MD029}
+5. Item {MD029}
+
+text
+
+- Item
+  0. Item
+  0. Item
+  0. Item
+- Item
+  1. Item {MD029}
+  2. Item {MD029}
+  3. Item {MD029}
+- Item
+  0. Item
+  1. Item {MD029}
+  2. Item {MD029}
+- Item