Add rules to prefer collapsed over full references

Closes GH-192.
Closes GH-212.

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>

doc/rules.md

@@ -125,6 +125,8 @@ Rules][external].
 *   [`no-table-indentation`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-table-indentation) — warn when tables are indented
 *   [`no-tabs`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-tabs) — warn when hard tabs are used instead of spaces
 *   [`no-undefined-references`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-undefined-references) — warn when references to undefined definitions are found
+*   [`no-unneeded-full-reference-image`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-unneeded-full-reference-image) — warn when full reference images are used if they can be collapsed
+*   [`no-unneeded-full-reference-link`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-unneeded-full-reference-link) — warn when full reference links are used if they can be collapsed
 *   [`no-unused-definitions`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-unused-definitions) — warn when unused definitions are found
 *   [`ordered-list-marker-style`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-ordered-list-marker-style) — warn when the markers of ordered lists violate a given style
 *   [`ordered-list-marker-value`](https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-ordered-list-marker-value) — warn when the marker value of ordered lists violates a given style

packages/remark-lint-no-unneeded-full-reference-image/index.js

@@ -0,0 +1,65 @@
+/**
+ * @author Titus Wormer
+ * @copyright 2019 Titus Wormer
+ * @license MIT
+ * @module no-unneeded-full-reference-image
+ * @fileoverview
+ *   Warn when full reference images are used that could be collapsed.
+ *
+ *   Full references (such as `[Remark][remark]`) can also be written as a
+ *   collapsed reference (`[Remark][]`) if normalising the reference text yields
+ *   the label.
+ *
+ * @example {"name": "valid.md"}
+ *
+ *   ![alpha][]
+ *   ![Bravo][]
+ *   ![Charlie][delta]
+ *
+ * @example {"name": "invalid.md", "label": "input"}
+ *
+ *   ![alpha][alpha]
+ *   ![Bravo][bravo]
+ *   ![charlie][Charlie]
+ *
+ * @example {"name": "invalid.md", "label": "output"}
+ *
+ *   1:1-1:16: Remove the image label as it matches the reference text
+ *   2:1-2:16: Remove the image label as it matches the reference text
+ *   3:1-3:20: Remove the image label as it matches the reference text
+ */
+
+'use strict'
+
+var rule = require('unified-lint-rule')
+var visit = require('unist-util-visit')
+var generated = require('unist-util-generated')
+var collapseWhiteSpace = require('collapse-white-space')
+
+module.exports = rule(
+  'remark-lint:no-unneeded-full-reference-image',
+  noUnneededFullReferenceImage
+)
+
+var reason = 'Remove the image label as it matches the reference text'
+
+function noUnneededFullReferenceImage(tree, file) {
+  visit(tree, 'imageReference', visitor)
+
+  function visitor(node) {
+    if (
+      generated(node) ||
+      node.referenceType !== 'full' ||
+      normalize(node.alt) !== node.identifier
+    ) {
+      return
+    }
+
+    file.message(reason, node)
+  }
+}
+
+// See: <https://github.com/remarkjs/remark/blob/cc7867b/packages/remark-parse/lib/util/normalize.js>
+function normalize(value) {
+  return collapseWhiteSpace(value).toLowerCase()
+}

packages/remark-lint-no-unneeded-full-reference-image/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "remark-lint-no-unneeded-full-reference-image",
+  "version": "0.0.0",
+  "description": "remark-lint rule to warn when full reference images are used if they can be collapsed",
+  "license": "MIT",
+  "keywords": [
+    "remark",
+    "lint",
+    "rule",
+    "full",
+    "collapsed",
+    "reference",
+    "image"
+  ],
+  "repository": "https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-unneeded-full-reference-image",
+  "bugs": "https://github.com/remarkjs/remark-lint/issues",
+  "author": "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)",
+  "contributors": [
+    "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
+  ],
+  "files": [
+    "index.js"
+  ],
+  "dependencies": {
+    "collapse-white-space": "^1.0.0",
+    "unified-lint-rule": "^1.0.0",
+    "unist-util-generated": "^1.1.0",
+    "unist-util-visit": "^1.4.0"
+  },
+  "xo": false
+}

packages/remark-lint-no-unneeded-full-reference-image/readme.md

@@ -0,0 +1,154 @@
+<!--This file is generated-->
+
+# remark-lint-no-unneeded-full-reference-image
+
+[![Build][build-badge]][build]
+[![Coverage][coverage-badge]][coverage]
+[![Downloads][downloads-badge]][downloads]
+[![Size][size-badge]][size]
+[![Sponsors][sponsors-badge]][collective]
+[![Backers][backers-badge]][collective]
+[![Chat][chat-badge]][chat]
+
+Warn when full reference images are used that could be collapsed.
+
+Full references (such as `[Remark][remark]`) can also be written as a
+collapsed reference (`[Remark][]`) if normalising the reference text yields
+the label.
+
+## Presets
+
+This rule is not included in any default preset
+
+## Example
+
+##### `valid.md`
+
+###### In
+
+```markdown
+![alpha][]
+![Bravo][]
+![Charlie][delta]
+```
+
+###### Out
+
+No messages.
+
+##### `invalid.md`
+
+###### In
+
+```markdown
+![alpha][alpha]
+![Bravo][bravo]
+![charlie][Charlie]
+```
+
+###### Out
+
+```text
+1:1-1:16: Remove the image label as it matches the reference text
+2:1-2:16: Remove the image label as it matches the reference text
+3:1-3:20: Remove the image label as it matches the reference text
+```
+
+## Install
+
+[npm][]:
+
+```sh
+npm install remark-lint-no-unneeded-full-reference-image
+```
+
+## Use
+
+You probably want to use it on the CLI through a config file:
+
+```diff
+ ...
+ "remarkConfig": {
+   "plugins": [
+     ...
+     "lint",
++    "lint-no-unneeded-full-reference-image",
+     ...
+   ]
+ }
+ ...
+```
+
+Or use it on the CLI directly
+
+```sh
+remark -u lint -u lint-no-unneeded-full-reference-image readme.md
+```
+
+Or use this on the API:
+
+```diff
+ var remark = require('remark');
+ var report = require('vfile-reporter');
+
+ remark()
+   .use(require('remark-lint'))
++  .use(require('remark-lint-no-unneeded-full-reference-image'))
+   .process('_Emphasis_ and **importance**', function (err, file) {
+     console.error(report(err || file));
+   });
+```
+
+## Contribute
+
+See [`contributing.md`][contributing] in [`remarkjs/.github`][health] for ways
+to get started.
+See [`support.md`][support] for ways to get help.
+
+This project has a [Code of Conduct][coc].
+By interacting with this repository, organisation, or community you agree to
+abide by its terms.
+
+## License
+
+[MIT][license] © [Titus Wormer][author]
+
+[build-badge]: https://img.shields.io/travis/remarkjs/remark-lint/master.svg
+
+[build]: https://travis-ci.org/remarkjs/remark-lint
+
+[coverage-badge]: https://img.shields.io/codecov/c/github/remarkjs/remark-lint.svg
+
+[coverage]: https://codecov.io/github/remarkjs/remark-lint
+
+[downloads-badge]: https://img.shields.io/npm/dm/remark-lint-no-unneeded-full-reference-image.svg
+
+[downloads]: https://www.npmjs.com/package/remark-lint-no-unneeded-full-reference-image
+
+[size-badge]: https://img.shields.io/bundlephobia/minzip/remark-lint-no-unneeded-full-reference-image.svg
+
+[size]: https://bundlephobia.com/result?p=remark-lint-no-unneeded-full-reference-image
+
+[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
+
+[backers-badge]: https://opencollective.com/unified/backers/badge.svg
+
+[collective]: https://opencollective.com/unified
+
+[chat-badge]: https://img.shields.io/badge/join%20the%20community-on%20spectrum-7b16ff.svg
+
+[chat]: https://spectrum.chat/unified/remark
+
+[npm]: https://docs.npmjs.com/cli/install
+
+[health]: https://github.com/remarkjs/.github
+
+[contributing]: https://github.com/remarkjs/.github/blob/master/contributing.md
+
+[support]: https://github.com/remarkjs/.github/blob/master/support.md
+
+[coc]: https://github.com/remarkjs/.github/blob/master/code-of-conduct.md
+
+[license]: https://github.com/remarkjs/remark-lint/blob/master/license
+
+[author]: https://wooorm.com

packages/remark-lint-no-unneeded-full-reference-link/index.js

@@ -0,0 +1,71 @@
+/**
+ * @author Titus Wormer
+ * @copyright 2019 Titus Wormer
+ * @license MIT
+ * @module no-unneeded-full-reference-link
+ * @fileoverview
+ *   Warn when full reference links are used that could be collapsed.
+ *
+ *   Full references (such as `[Remark][remark]`) can also be written as a
+ *   collapsed reference (`[Remark][]`) if normalising the reference text yields
+ *   the label.
+ *
+ * @example {"name": "valid.md"}
+ *
+ *   [alpha][]
+ *   [Bravo][]
+ *   [Charlie][delta]
+ *
+ *   This only works if the link text is a `text` node:
+ *   [`echo`][]
+ *   [*foxtrot*][]
+ *
+ * @example {"name": "invalid.md", "label": "input"}
+ *
+ *   [alpha][alpha]
+ *   [Bravo][bravo]
+ *   [charlie][Charlie]
+ *
+ * @example {"name": "invalid.md", "label": "output"}
+ *
+ *   1:1-1:15: Remove the link label as it matches the reference text
+ *   2:1-2:15: Remove the link label as it matches the reference text
+ *   3:1-3:19: Remove the link label as it matches the reference text
+ */
+
+'use strict'
+
+var rule = require('unified-lint-rule')
+var visit = require('unist-util-visit')
+var generated = require('unist-util-generated')
+var collapseWhiteSpace = require('collapse-white-space')
+
+module.exports = rule(
+  'remark-lint:no-unneeded-full-reference-link',
+  noUnneededFullReferenceLink
+)
+
+var reason = 'Remove the link label as it matches the reference text'
+
+function noUnneededFullReferenceLink(tree, file) {
+  visit(tree, 'linkReference', visitor)
+
+  function visitor(node) {
+    if (
+      generated(node) ||
+      node.referenceType !== 'full' ||
+      node.children.length !== 1 ||
+      node.children[0].type !== 'text' ||
+      normalize(node.children[0].value) !== node.identifier
+    ) {
+      return
+    }
+
+    file.message(reason, node)
+  }
+}
+
+// See: <https://github.com/remarkjs/remark/blob/cc7867b/packages/remark-parse/lib/util/normalize.js>
+function normalize(value) {
+  return collapseWhiteSpace(value).toLowerCase()
+}

packages/remark-lint-no-unneeded-full-reference-link/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "remark-lint-no-unneeded-full-reference-link",
+  "version": "0.0.0",
+  "description": "remark-lint rule to warn when full reference links are used if they can be collapsed",
+  "license": "MIT",
+  "keywords": [
+    "remark",
+    "lint",
+    "rule",
+    "full",
+    "collapsed",
+    "reference",
+    "link"
+  ],
+  "repository": "https://github.com/remarkjs/remark-lint/tree/master/packages/remark-lint-no-unneeded-full-reference-link",
+  "bugs": "https://github.com/remarkjs/remark-lint/issues",
+  "author": "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)",
+  "contributors": [
+    "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
+  ],
+  "files": [
+    "index.js"
+  ],
+  "dependencies": {
+    "collapse-white-space": "^1.0.0",
+    "unified-lint-rule": "^1.0.0",
+    "unist-util-generated": "^1.1.0",
+    "unist-util-visit": "^1.4.0"
+  },
+  "xo": false
+}