Merge pull request #298 from lxsymington/enforce-nesting

[#197] - New rule to enforce nesting

src/rules/index.js

@@ -36,6 +36,7 @@ import operatorNoNewlineBefore from "./operator-no-newline-before";
 import operatorNoUnspaced from "./operator-no-unspaced";
 import partialNoImport from "./partial-no-import";
 import percentPlaceholderPattern from "./percent-placeholder-pattern";
+import selectorNestCombinators from "./selector-nest-combinators";
 import selectorNoRedundantNestingSelector from "./selector-no-redundant-nesting-selector";
 
 export default {
@@ -77,5 +78,6 @@ export default {
   "operator-no-unspaced": operatorNoUnspaced,
   "percent-placeholder-pattern": percentPlaceholderPattern,
   "partial-no-import": partialNoImport,
+  "selector-nest-combinators": selectorNestCombinators,
   "selector-no-redundant-nesting-selector": selectorNoRedundantNestingSelector
 };

src/rules/selector-nest-combinators/README.md

@@ -0,0 +1,221 @@
+# selector-nest-combinators
+
+Require or disallow nesting of combinators in selectors
+
+```scss
+/* Examples of selectors without nesting of combinators */
+.foo .bar {}
+
+.foo.bar {}
+
+.foo > .bar {}
+
+.foo:hover {}
+
+/* Corresponding selectors with combinators nested */
+.foo {
+  .bar {}
+}
+
+.foo {
+  &.bar {}
+}
+
+.foo {
+  & > .bar {}
+}
+
+.foo {
+  &:hover {}
+}
+```
+
+## Options
+
+`string`: `"always"|"never"`
+
+### `"always"`
+
+*Every combinator* in a selector *must be* nested where possible without altering the existing resolved selector.
+
+Sections of selectors preceding a parent selector are ignored with `always`.
+e.g.
+
+```scss
+.foo {
+  .bar.baz & {}
+}
+```
+
+Sections of selectors within pseudo selectors are also ignored with `always`.
+e.g.
+
+```scss
+.foo {
+  &:not(.bar .baz) {}
+}
+```
+
+while this could be refactored to:
+
+```scss
+.bar {
+  .baz {
+    .foo:not(&) {}
+  }
+}
+```
+
+There are variances in the way this is compiled between compilers, therefore for the purposes of this rule the selector sections within pseudo selectors are being ignored.
+
+The following patterns are considered warnings:
+
+```scss
+.foo .bar {}
+```
+
+```scss
+.foo.bar {}
+```
+
+```scss
+.foo > .bar {}
+```
+
+```scss
+.foo:hover {}
+```
+
+```scss
+a[href] {}
+```
+
+```scss
+* + li {}
+```
+
+```scss
+:nth-child(2n - 1):last-child {}
+```
+
+The following patterns are *not* considered warnings:
+
+```scss
+.foo {
+  .bar {}
+}
+```
+
+```scss
+.foo {
+  &.bar {}
+}
+```
+
+```scss
+.foo {
+  & > .bar {}
+}
+```
+
+```scss
+.foo {
+  &:hover {}
+}
+```
+
+```scss
+a {
+  &[href] {}
+}
+```
+
+```scss
+* {
+  & + li {}
+}
+```
+
+```scss
+:nth-child(2n - 1) {
+  &:last-child {}
+}
+```
+
+### `"never"`
+
+Nested of selectors are not allowed.
+
+The following patterns are considered warnings:
+
+```scss
+.foo {
+  .bar {}
+}
+```
+
+```scss
+.foo {
+  &.bar {}
+}
+```
+
+```scss
+.foo {
+  & > .bar {}
+}
+```
+
+```scss
+.foo {
+  &:hover {}
+}
+```
+
+```scss
+a {
+  &[href] {}
+}
+```
+
+```scss
+* {
+  & + li {}
+}
+```
+
+```scss
+:nth-child(2n - 1) {
+  &:last-child {}
+}
+```
+
+The following patterns are *not* considered warnings:
+
+```scss
+.foo .bar {}
+```
+
+```scss
+.foo.bar {}
+```
+
+```scss
+.foo > .bar {}
+```
+
+```scss
+.foo:hover {}
+```
+
+```scss
+a[href] {}
+```
+
+```scss
+* + li {}
+```
+
+```scss
+:nth-child(2n - 1):last-child {}
+```