Add simple/concrete example of custom rule package for publishing (fixes

 #133).

doc/CustomRules.md

@@ -1,7 +1,7 @@
 # Custom Rules
 
 In addition to its built-in rules, `markdownlint` lets you enhance the linting experience by passing a list of custom rules using the [`options.customRules` property](../README.md#optionscustomrules).
-Custom rules can do everything the built-in rules can and are defined inline or imported from another package ([keyword `markdownlint-rules` on npm](https://www.npmjs.com/search?q=keywords:markdownlint-rules)).
+Custom rules can do everything the built-in rules can and are defined inline or imported from another package ([keyword `markdownlint-rule` on npm](https://www.npmjs.com/search?q=keywords:markdownlint-rule)).
 Custom rules can be disabled, enabled, and customized using the same syntax as built-in rules.
 
 ## Authoring
@@ -52,8 +52,9 @@ A rule is implemented as an `Object` with four required properties:
 ## Examples
 
 - [Simple rules used by the project's test cases](../test/rules)
-  - Includes [sample package configuration for npm](../test/rules/package.json)
 - [Code for all `markdownlint` built-in rules](../lib)
+- [Package configuration for publishing to npm](../test/rules/npm)
+  - Each package should export a single rule object
 
 ## References
 
@@ -62,15 +63,15 @@ A rule is implemented as an `Object` with four required properties:
 
 ## Params
 
-Linting the Markdown document:
+The Markdown document:
 
 ```markdown
 # Title
 
 Text *text* text.
 ```
 
-Would create a `params` object like:
+Yields the `params` object:
 
 ```json
 {

test/markdownlint-test.js

@@ -7,7 +7,7 @@ const tv4 = require("tv4");
 const markdownlint = require("../lib/markdownlint");
 const shared = require("../lib/shared");
 const rules = require("../lib/rules");
-const customRules = require("./rules");
+const customRules = require("./rules/rules.js");
 const defaultConfig = require("./markdownlint-test-default-config.json");
 const configSchema = require("../schema/markdownlint-config-schema.json");
 
@@ -1984,6 +1984,26 @@ module.exports.customRulesConfig = function customRulesConfig(test) {
   });
 };
 
+module.exports.customRulesNpmPackage = function customRulesNpmPackage(test) {
+  test.expect(2);
+  const options = {
+    "customRules": [ require("./rules/npm") ],
+    "strings": {
+      "string": "# Text\n\n---\n\nText"
+    },
+    "resultVersion": 0
+  };
+  markdownlint(options, function callback(err, actualResult) {
+    test.ifError(err);
+    const expectedResult = {};
+    expectedResult.string = {
+      "sample-rule": [ 3 ]
+    };
+    test.deepEqual(actualResult, expectedResult, "Undetected issues.");
+    test.done();
+  });
+};
+
 module.exports.customRulesBadProperty = function customRulesBadProperty(test) {
   test.expect(76);
   [

test/rules/package.json → test/rules/npm/package.json

@@ -1,13 +1,13 @@
 {
-  "name": "markdownlint-rules-test",
+  "name": "markdownlint-rule-sample",
   "version": "0.0.1",
-  "description": "Package of markdownlint custom rules used for testing",
-  "main": "rules.js",
+  "description": "Package for markdownlint custom rule sample",
+  "main": "sample-rule.js",
   "author": "David Anson (https://dlaa.me/)",
   "homepage": "https://github.com/DavidAnson/markdownlint",
   "license": "MIT",
   "keywords": [
-    "markdownlint-rules"
+    "markdownlint-rule"
   ],
   "private": true
 }

test/rules/npm/sample-rule.js

@@ -0,0 +1,19 @@
+// @ts-check
+
+"use strict";
+
+module.exports = {
+  "names": [ "sample-rule" ],
+  "description": "Sample rule",
+  "tags": [ "sample" ],
+  "function": function rule(params, onError) {
+    params.tokens.forEach((token) => {
+      if (token.type === "hr") {
+        onError({
+          "lineNumber": token.lineNumber,
+          "detail": "Sample error for hr"
+        });
+      }
+    });
+  }
+};