Adding a new rule, no-alt-text as per Issue #75

README.md

@@ -86,6 +86,7 @@ playground for learning and exploring.
 * **[MD042](doc/Rules.md#md042)** *no-empty-links* - No empty links
 * **[MD043](doc/Rules.md#md043)** *required-headers* - Required header structure
 * **[MD044](doc/Rules.md#md044)** *proper-names* - Proper names should have the correct capitalization
+* **[MD045](doc/Rules.md#md045)** *no-alt-text* - Images should have ALT Text attribute
 
 See [Rules.md](doc/Rules.md) for more details.
 
@@ -113,6 +114,8 @@ See [Rules.md](doc/Rules.md) for more details.
 * **ul** - MD004, MD005, MD006, MD007, MD030, MD032
 * **url** - MD034
 * **whitespace** - MD009, MD010, MD012, MD027, MD028, MD030, MD037, MD038, MD039
+* **accessibility** - MD045
+* **images** - MD045
 
 ## Configuration
 

doc/Rules.md

@@ -1236,3 +1236,13 @@ the proper capitalization, specify the desired letter case in the `names` array:
     ]
 
 Set the `code_blocks` parameter to `false` to disable this rule for code blocks.
+
+<a name="md045"></a>
+
+## MD045 - Images should have ALT Text attribute
+
+Tags: images, accessibility
+
+Aliases: no-alt-text
+
+This rule is triggered when an image is found with no alt text. This is a key concern for accessibility. [Guidance on how to write alt text for images](https://www.phase2technology.com/blog/no-more-excuses-definitive-guide-alt-text-field).

lib/rules.js

@@ -1202,5 +1202,23 @@ module.exports = [
         }
       });
     }
+  },
+  {
+    "name": "MD045",
+    "desc": "Images should have ALT Text attribute",
+    "tags": [ "images", "accessibility" ],
+    "aliases": [ "no-alt-text" ],
+    "regexp": null,
+    "func": function MD045(params, errors) {
+      forEachInlineChild(params, "image", function forToken(token) {
+        if (token.content === "") {
+          token.attrs.forEach(function forAttr(attr) {
+            if (attr[0] === "alt" && attr[1] === "") {
+              errors.add(token.lineNumber);
+            }
+          });
+        }
+      });
+    }
   }
 ];

schema/markdownlint-config-schema.json

@@ -954,6 +954,16 @@
       },
       "additionalProperties": false
     },
+    "MD045": {
+      "description": "MD045/no-alt-text - Images should have non-empty Alt Text",
+      "type": "boolean",
+      "default": true
+    },
+    "no-alt-text": {
+      "description": "MD045/no-alt-text - Images should have non-empty Alt Text",
+      "type": "boolean",
+      "default": true      
+    },
     "headers": {
       "description": "headers - MD001, MD002, MD003, MD018, MD019, MD020, MD021, MD022, MD023, MD024, MD025, MD026, MD036, MD041, MD043",
       "type": "boolean",

test/detailed-results-MD041-MD050.md

@@ -15,3 +15,7 @@ name wrong twice:
 MarkDownLint.
 
 A [normal](link) and an [empty one]() and a [fragment](#one).
+
+An image without alt text ![](image.jpg)
+
+![](image.jpg)

test/detailed-results-MD041-MD050.results.json

@@ -45,7 +45,7 @@
         "errorRange": [25, 13]
     },
     {
-        "lineNumber": 18,
+        "lineNumber": 22,
         "ruleName": "MD043",
         "ruleAlias": "required-headers",
         "ruleDescription": "Required header structure",
@@ -79,5 +79,23 @@
         "errorDetail": "Expected: markdownlint; Actual: MarkDownLint",
         "errorContext": null,
         "errorRange": [1, 12]
+    },
+    {
+        "lineNumber": 19,
+        "ruleName": "MD045",
+        "ruleAlias": "no-alt-text",
+        "ruleDescription": "Images should have ALT Text attribute",
+        "errorDetail": null,
+        "errorContext": null,
+        "errorRange": null
+    },
+    {
+        "lineNumber": 21,
+        "ruleName": "MD045",
+        "ruleAlias": "no-alt-text",
+        "ruleDescription": "Images should have ALT Text attribute",
+        "errorDetail": null,
+        "errorContext": null,
+        "errorRange": null
     }
 ]

test/markdownlint-test.js

@@ -966,7 +966,7 @@ module.exports.missingStringValue = function missingStringValue(test) {
 };
 
 module.exports.ruleNamesUpperCase = function ruleNamesUpperCase(test) {
-  test.expect(40);
+  test.expect(41);
   rules.forEach(function forRule(rule) {
     test.equal(rule.name, rule.name.toUpperCase(), "Rule name not upper-case.");
   });
@@ -974,7 +974,7 @@ module.exports.ruleNamesUpperCase = function ruleNamesUpperCase(test) {
 };
 
 module.exports.uniqueAliases = function uniqueAliases(test) {
-  test.expect(80);
+  test.expect(82);
   var tags = [];
   rules.forEach(function forRule(rule) {
     Array.prototype.push.apply(tags, rule.tags);
@@ -991,7 +991,7 @@ module.exports.uniqueAliases = function uniqueAliases(test) {
 };
 
 module.exports.readme = function readme(test) {
-  test.expect(104);
+  test.expect(108);
   var tagToRules = {};
   rules.forEach(function forRule(rule) {
     rule.tags.forEach(function forTag(tag) {
@@ -1053,7 +1053,7 @@ module.exports.readme = function readme(test) {
 };
 
 module.exports.doc = function doc(test) {
-  test.expect(303);
+  test.expect(310);
   fs.readFile("doc/Rules.md", shared.utf8Encoding,
     function readFile(err, contents) {
       test.ifError(err);

test/no_alt_text.json

@@ -0,0 +1,4 @@
+{
+  "default": true,
+  "MD045": true
+}

test/no_alt_text.md

@@ -0,0 +1,3 @@
+# This is an image link without any alt text
+
+![](image.jpg) {MD045}