mdast-lint-blank-lines-1-0-2 init

.babelrc

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+{
+  "presets": ["es2015"]
+}

.editorconfig

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+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 2
+

.eslintrc

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+{
+  "extends": "airbnb",
+  "parser": "babel-eslint",
+  "env": {
+    "node": true
+  }
+}

.gitignore

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+.DS_Store
+*.log
+node_modules

README.md

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+# mdast-lint-blank-lines-1-0-2
+
+This [mdast-lint](https://github.com/wooorm/mdast-lint) rule was created for [free-programming-books-lint](https://github.com/vhf/free-programming-books-lint) to enforce [free-programming-books](https://github.com/vhf/free-programming-books) [formatting guidelines](https://github.com/vhf/free-programming-books/blob/master/CONTRIBUTING.md#formatting).
+
+This rule ensures that a file has
+
+- 2 empty lines between last link and new section
+- 1 empty line between heading & first link of its section
+- 0 empty line between two list items
+- 1 empty line at the end of each .md file
+
+```Text
+<!-- Invalid -->
+
+[...]
+* [An Awesome Book](http://example.com/example.html)
+
+### Example
+* [Another Awesome Book](http://example.com/book.html)
+
+* [Some Other Book](http://example.com/other.html)
+
+<!-- Valid -->
+
+[...]
+* [An Awesome Book](http://example.com/example.html)
+
+
+### Example
+
+* [Another Awesome Book](http://example.com/book.html)
+* [Some Other Book](http://example.com/other.html)
+```
+
+## Using the rule
+
+### Via `.mdastrc`
+
+```bash
+npm install -g mdast
+npm install -g mdast-lint
+npm install mdast-lint-blank-lines-1-0-2 # local install!
+```
+
+Then, set up your `.mdastrc`:
+
+```JSON
+{
+  "plugins": {
+    "mdast-lint": {
+      "external": ["mdast-lint-blank-lines-1-0-2"]
+    }
+  }
+}
+```
+
+Now you can use the following command to run the lint:
+
+```bash
+mdast --no-stdout xxx.md
+```
+
+### Via CLI
+
+```bash
+npm install -g mdast
+npm install -g mdast-lint
+npm install -g mdast-lint-blank-lines-1-0-2 # global install!
+mdast --no-stdout -u mdast-lint="external:[\"mdast-lint-blank-lines-1-0-2\"]" xxx.md
+```
+
+Note that the `lint=<lint_options>` option only works with `mdast >= 1.1.1`.
+
+This `README.md` is based on [this one](https://github.com/chcokr/mdast-lint-sentence-newline/blob/250b106c9e19b387270099cf16f17a84643f8944/README.md) by [@chcokr](https://github.com/chcokr) (MIT).

dist/blank-lines.js

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+'use strict';
+
+var visit = require('unist-util-visit');
+var position = require('mdast-util-position');
+
+function isApplicable(node) {
+  return ['paragraph', 'heading', 'list'].indexOf(node.type) !== -1;
+}
+
+function blankLines(ast, file, preferred, done) {
+  visit(ast, function (node, index, parent) {
+    var next = parent && parent.children[index + 1];
+
+    if (position.generated(node)) {
+      return;
+    }
+
+    if (next && isApplicable(node) && isApplicable(next)) {
+      if (node.type === 'heading' && next.type === 'heading') {
+        if (position.start(next).line !== position.end(node).line + 2) {
+          file.warn('Incorrect number of blank lines between headings', node);
+        }
+      } else if (node.type === 'heading' && next.type !== 'heading') {
+        if (position.start(next).line - position.end(node).line !== 2) {
+          file.warn('Incorrect number of blank lines between heading and section', node);
+        }
+      } else if (node.type === 'list') {
+        if (position.start(next).line - position.end(node).line !== 3) {
+          file.warn('Incorrect number of blank lines between last section and next heading', node);
+        }
+      }
+    }
+  });
+
+  done();
+}
+
+module.exports = blankLines;

lib/blank-lines.js

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+const visit = require('unist-util-visit');
+const position = require('mdast-util-position');
+
+function isApplicable(node) {
+  return [
+    'paragraph',
+    'heading',
+    'list',
+  ].indexOf(node.type) !== -1;
+}
+
+function blankLines(ast, file, preferred, done) {
+  visit(ast, (node, index, parent) => {
+    const next = parent && parent.children[index + 1];
+
+    if (position.generated(node)) {
+      return;
+    }
+
+    if (next && isApplicable(node) && isApplicable(next)) {
+      if (node.type === 'heading' && next.type === 'heading') {
+        if (position.start(next).line !== position.end(node).line + 2) {
+          file.warn('Incorrect number of blank lines between headings', node);
+        }
+      } else if (node.type === 'heading' && next.type !== 'heading') {
+        if (position.start(next).line - position.end(node).line !== 2) {
+          file.warn('Incorrect number of blank lines between heading and section', node);
+        }
+      } else if (node.type === 'list') {
+        if (position.start(next).line - position.end(node).line !== 3) {
+          file.warn('Incorrect number of blank lines between last section and next heading', node);
+        }
+      }
+    }
+  });
+
+  done();
+}
+
+module.exports = blankLines;

package.json

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+{
+  "name": "mdast-lint-blank-lines-1-0-2",
+  "version": "0.1.0",
+  "description": "Checks that all titles are followed by 1 blank line, then no blank lines, then two blank lines before the next title",
+  "author": "Victor Felder <[email protected]>",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/vhf/mdast-lint-blank-lines-1-0-2.git"
+  },
+  "license": "MIT",
+  "dependencies": {
+    "mdast-util-position": "^1.0.0",
+    "unist-util-visit": "^1.0.0"
+  },
+  "devDependencies": {
+    "babel-core": "^6.3.17",
+    "babel-eslint": "^5.0.0-beta6",
+    "babel-preset-es2015": "^6.3.13",
+    "eslint": "^1.10.3",
+    "eslint-config-airbnb": "^2.1.1",
+    "eslint-plugin-react": "^3.11.3"
+  },
+  "scripts": {
+    "build": "babel lib -d dist"
+  },
+  "bugs": {
+    "url": "https://github.com/vhf/mdast-lint-blank-lines-1-0-2/issues"
+  },
+  "homepage": "https://github.com/vhf/mdast-lint-blank-lines-1-0-2#readme",
+  "main": "dist/index.js"
+}