Merge branch 'DuncanmaMSFT-master' into next

README.md

@@ -86,11 +86,13 @@ 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 alternate text (alt text)
 
 See [Rules.md](doc/Rules.md) for more details.
 
 ## Tags
 
+* **accessibility** - MD045
 * **atx** - MD018, MD019
 * **atx_closed** - MD020, MD021
 * **blank_lines** - MD012, MD022, MD031, MD032
@@ -103,6 +105,7 @@ See [Rules.md](doc/Rules.md) for more details.
   MD024, MD025, MD026, MD036, MD041, MD043
 * **hr** - MD035
 * **html** - MD033
+* **images** - MD045
 * **indentation** - MD005, MD006, MD007, MD027
 * **language** - MD040
 * **line_length** - MD013

doc/Rules.md

@@ -1243,3 +1243,35 @@ 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 alternate text (alt text)
+
+Tags: accessibility, images
+
+Aliases: no-alt-text
+
+This rule is triggered when an image is missing alternate text (alt text) information.
+Alternate text is important for accessibility, describing the content of an image for
+people who may not be able to see it.
+
+Alternate text is commonly specified inline as:
+
+```md
+![Alternate text](image.jpg)
+```
+
+Or with reference syntax as:
+
+```md
+![Alternate text][ref]
+
+...
+
+[ref]: image.jpg "Optional title"
+```
+
+Guidance for writing alternate text is available from the [W3C](https://www.w3.org/WAI/alt/),
+[Wikipedia](https://en.wikipedia.org/wiki/Alt_attribute), and
+[other locations](https://www.phase2technology.com/blog/no-more-excuses-definitive-guide-alt-text-field).

lib/rules.js

@@ -1219,5 +1219,19 @@ module.exports = [
         }
       });
     }
+  },
+  {
+    "name": "MD045",
+    "desc": "Images should have alternate text (alt text)",
+    "tags": [ "accessibility", "images" ],
+    "aliases": [ "no-alt-text" ],
+    "regexp": null,
+    "func": function MD045(params, errors) {
+      forEachInlineChild(params, "image", function forToken(token) {
+        if (token.content === "") {
+          errors.add(token.lineNumber);
+        }
+      });
+    }
   }
 ];

schema/markdownlint-config-schema.json

@@ -956,6 +956,16 @@
       },
       "additionalProperties": false
     },
+    "MD045": {
+      "description": "MD045/no-alt-text - Images should have alternate text (alt text)",
+      "type": "boolean",
+      "default": true
+    },
+    "no-alt-text": {
+      "description": "MD045/no-alt-text - Images should have alternate text (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",
@@ -1060,6 +1070,16 @@
       "description": "spelling - MD044",
       "type": "boolean",
       "default": true
+    },
+    "accessibility": {
+      "description": "accessibility - MD045",
+      "type": "boolean",
+      "default": true
+    },
+    "images": {
+      "description": "images - MD045",
+      "type": "boolean",
+      "default": true
     }
   },
   "additionalProperties": false

test/detailed-results-MD041-MD050.md

@@ -15,3 +15,5 @@ name wrong twice:
 MarkDownLint.
 
 A [normal](link) and an [empty one]() and a [fragment](#one).
+
+An image without alternate text ![](image.jpg)

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

@@ -45,7 +45,7 @@
         "errorRange": [25, 13]
     },
     {
-        "lineNumber": 18,
+        "lineNumber": 20,
         "ruleName": "MD043",
         "ruleAlias": "required-headers",
         "ruleDescription": "Required header structure",
@@ -79,5 +79,14 @@
         "errorDetail": "Expected: markdownlint; Actual: MarkDownLint",
         "errorContext": null,
         "errorRange": [1, 12]
+    },
+    {
+        "lineNumber": 19,
+        "ruleName": "MD045",
+        "ruleAlias": "no-alt-text",
+        "ruleDescription": "Images should have alternate text (alt text)",
+        "errorDetail": null,
+        "errorContext": null,
+        "errorRange": null
     }
 ]

test/markdownlint-test.js

@@ -965,7 +965,7 @@ 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.");
   });
@@ -973,7 +973,7 @@ 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);
@@ -990,7 +990,7 @@ 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) {
@@ -1052,7 +1052,7 @@ 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.md

@@ -0,0 +1,26 @@
+# Images with and without alternate text
+
+![Alternate text](image.jpg)
+
+![](image.jpg) {MD045}
+
+![Alternate text](image.jpg "Title")
+
+![](image.jpg "Title") {MD045}
+
+Image without alternate text ![](image.jpg) in a sentence. {MD045}
+
+Reference image with alternate text ![Alternate text][notitle]
+
+Reference image without alternate text ![][notitle] {MD045}
+
+Reference image with alternate text and title ![Alternate text][title]
+
+Reference image without alternate text and title ![][title] {MD045}
+
+Link to image with alternate text [![Alternate text](image.jpg)](image.jpg)
+
+Link to image without alternate text [![](image.jpg)](image.jpg) {MD045}
+
+[notitle]: image.jpg
+[title]: image.jpg "Title"