Implement new rule no-excessive-empty-lines (fixes #1015)

.gitignore

@@ -31,3 +31,5 @@ node_modules
 
 # Users Environment Variables
 .lock-wscript
+
+.vscode

CONTRIBUTING.md

@@ -73,7 +73,7 @@ By making a contribution to this project, I certify that:
 
 ## Emoji Cheatsheet
 
-When creating creating commits or updating the CHANGELOG, please **start** the commit message or update with one of the following applicable Emoji. Emoji should not be used at the start of issue or pull request titles.
+When creating commits or updating the CHANGELOG, please **start** the commit message or update with one of the following applicable Emoji. Emoji should not be used at the start of issue or pull request titles.
 
 * :art: `:art:` when improving the format/structure of the code
 * :racehorse: `:racehorse:` when improving performance

docs/rules/no-excessive-empty-lines.md

@@ -0,0 +1,47 @@
+# No Excessive Empty Lines
+
+Rule `no-excessive-empty-lines` will disallow excessive amounts of empty lines.
+
+- Consecutive blank lines are not allowed
+- Blank lines at the start of a block are not allowed
+- Blank lines at the end of a block are not allowed
+
+## Options
+
+* `allow-consecutive`: `true`/`false` (defaults to `false`)
+* `allow-at-block-end`: `true`/`false` (defaults to `false`)
+* `allow-at-block-start`: `true`/`false` (defaults to `false`)`)
+
+## Examples
+
+When enabled the following are allowed:
+
+```scss
+.foo {
+  content: 'bar';
+  content: 'baz';
+
+  .waldo {
+    content: 'where';
+  }
+}
+```
+
+When enabled the following are disallowed:
+
+```scss
+
+
+.foo {
+  content: 'bar';
+  content: 'baz'
+
+
+  .waldo {
+    content: 'where'
+
+  }
+}
+
+
+```

index.js

@@ -310,7 +310,8 @@ sassLint.failOnError = function (results, options, configPath) {
       configOptions = this.getConfig(options, configPath).options;
 
   if (errorCount.count > 0) {
-    throw new exceptions.SassLintFailureError(errorCount.count + ' errors were detected in \n- ' + errorCount.files.join('\n- '));
+    const pluralized = errorCount.count === 1 ? 'error was' : 'errors were';
+    throw new exceptions.SassLintFailureError(errorCount.count + ' ' + pluralized + ' detected in \n- ' + errorCount.files.join('\n- '));
   }
 
   if (!isNaN(configOptions['max-warnings']) && warningCount.count > configOptions['max-warnings']) {

lib/rules/no-excessive-empty-lines.js

@@ -0,0 +1,127 @@
+'use strict';
+
+var helpers = require('../helpers');
+
+const countOccurences = function (str, substr) {
+  return str.split(substr).length - 1;
+};
+
+const checkNodeForEmptyness = function (node) {
+  if (node.type !== 'space') {
+    return false;
+  }
+
+  return countOccurences(node.content, '\n') > 1;
+};
+
+const addError = function (result, parser, message, line) {
+  return helpers.addUnique(result, {
+    'ruleId': parser.rule.name,
+    'line': line,
+    'column': 1,
+    message,
+    'severity': parser.severity
+  });
+};
+
+const multipleConsecutiveError = function (result, parser, line) {
+  return addError(result, parser, 'Multiple consecutive empty lines not allowed', line);
+};
+
+const startOfBlockError = function (result, parser, line) {
+  return addError(result, parser, 'Empty lines at start of block not allowed', line);
+};
+
+const endOfBlockError = function (result, parser, line) {
+  return addError(result, parser, 'Empty lines at end of block not allowed', line);
+};
+
+module.exports = {
+  'name': 'no-excessive-empty-lines',
+  'defaults': {
+    'allow-consecutive': false,
+    'allow-at-block-end': false,
+    'allow-at-block-start': false,
+  },
+  'detect': function (ast, parser) {
+    let result = [];
+
+    if (!parser.options['allow-consecutive']) {
+      const source = ast.toString();
+      const re = /^\n\n+/gm;
+      let m = null;
+      do {
+        m = re.exec(source);
+        if (m) {
+          const lineNumber = source
+            .substr(0, m.index)
+            .split('\n').length;
+
+          result = multipleConsecutiveError(result, parser, lineNumber);
+        }
+      } while (m);
+    }
+
+    const forbidAtStart = !parser.options['allow-at-block-start'];
+    const forbidAtEnd = !parser.options['allow-at-block-end'];
+
+    if (forbidAtStart || forbidAtEnd) {
+      ast.traverseByType('block', function (node) {
+        if (!Array.isArray(node.content) || node.content.length < 1) {
+          return true;
+        }
+
+        if (ast.syntax === 'scss') {
+          if (forbidAtStart) {
+            if (checkNodeForEmptyness(node.content[0])) {
+              result = startOfBlockError(result, parser, node.start.line + 1);
+            }
+          }
+
+          if (forbidAtEnd) {
+            const n = node.content[node.content.length - 1];
+            if (checkNodeForEmptyness(n)) {
+              result = endOfBlockError(result, parser, n.start.line + 1);
+            }
+          }
+        }
+        else if (ast.syntax === 'sass') {
+          if (forbidAtStart) {
+            if (node.content[0].type === 'space' &&
+              countOccurences(node.content[0].content, '\n')) {
+              result = startOfBlockError(result, parser, node.start.line);
+            }
+          }
+        }
+
+        return true;
+      });
+    }
+
+    if (!parser.options['allow-at-block-end']) {
+      ast.traverseByType('block', function (node) {
+        if (!Array.isArray(node.content) || node.content.length < 1) {
+          return true;
+        }
+
+        if (node.content[0].type !== 'space') {
+          return true;
+        }
+
+        if (countOccurences(node.content[0].content, '\n') > 1) {
+          result = helpers.addUnique(result, {
+            'ruleId': parser.rule.name,
+            'line': node.start.line + 1,
+            'column': 1,
+            'message': 'Empty lines at end of block not allowed',
+            'severity': parser.severity
+          });
+        }
+
+        return true;
+      });
+    }
+
+    return result;
+  }
+};

tests/rules/no-excessive-empty-lines.js

@@ -0,0 +1,35 @@
+'use strict';
+
+var lint = require('./_lint');
+
+//////////////////////////////
+// SCSS syntax tests
+//////////////////////////////
+describe('no excessive empty lines - scss', function () {
+  var file = lint.file('no-excessive-empty-lines.scss');
+
+  it('enforce', function (done) {
+    lint.test(file, {
+      'no-excessive-empty-lines': 1
+    }, function (data) {
+      lint.assert.equal(15, data.warningCount);
+      done();
+    });
+  });
+});
+
+//////////////////////////////
+// Sass syntax tests
+//////////////////////////////
+describe('no excessive empty lines - sass', function () {
+  var file = lint.file('no-excessive-empty-lines.sass');
+
+  it('enforce', function (done) {
+    lint.test(file, {
+      'no-excessive-empty-lines': 1
+    }, function (data) {
+      lint.assert.equal(15, data.warningCount);
+      done();
+    });
+  });
+});

tests/sass/no-excessive-empty-lines.sass

@@ -0,0 +1,93 @@
+.foo
+
+  content: 'foo'
+
+
+
+.foo
+  content: 'foo'
+.bar
+  content: 'bar'
+
+.foo
+  @include bar
+
+.foo
+  @include bar($qux)
+    content: 'foo'
+
+
+.foo
+  @include bar($qux)
+    content: 'foo'
+
+
+.foo
+
+  @include bar($qux)
+    content: 'foo'
+
+
+.foo
+  @include bar($qux)
+    &:after
+      content: 'foo'
+
+
+
+.foo
+
+  &__bar
+    content: 'foo'
+
+
+  content: 'foo'
+
+.foo
+  content: 'foo'
+
+  &__bar
+    content: 'foo'
+
+
+.foo
+  content: 'foo'
+
+  &__bar
+    content: 'foo'
+
+
+
+.foo
+  &:before
+    content: 'foo'
+
+
+.foo
+  content: 'foo'
+
+  &::first-line
+    content: 'foo'
+
+
+h1
+  content: 'foo'
+h2
+  content: 'foo'
+h3
+  content: 'foo'
+h4
+  content: 'foo'
+
+
+.foo + .bar
+  content: 'foo'
+.foo + .bar,
+h2
+  content: 'foo'
+
+
+[type=text]
+  content: 'foo'
+h1.foo
+  content: 'foo'