Add at-use-no-redundant-alias rule

src/rules/at-use-no-redundant-alias/README.md

@@ -0,0 +1,38 @@
+# at-use-no-redundant-alias
+
+By default, the module's namespace is just the last component of the module’s URL.
+This rule is to disallow redundant namespace aliases.
+
+```scss
+@use "foo" as foo;
+/**           ↑
+ * Disallow this */
+```
+
+The following patterns are considered warnings:
+
+```scss
+@use "foo" as foo;
+```
+
+```scss
+@use "sass:math" as math;
+```
+
+```scss
+@use "src/corners" as corners;
+```
+
+The following patterns are _not_ considered warnings:
+
+```scss
+@use "foo" as bar;
+```
+
+```scss
+@use "sass:math";
+```
+
+```scss
+@use "src/corners" as c;
+```

src/rules/at-use-no-redundant-alias/__tests__/index.js

@@ -0,0 +1,95 @@
+"use strict";
+
+const { messages, ruleName } = require("..");
+
+testRule({
+  ruleName,
+  config: [true],
+  customSyntax: "postcss-scss",
+
+  accept: [
+    {
+      code: `
+      @use "foo";
+    `,
+      description: "Default namespace"
+    },
+    {
+      code: `
+      @use "foo/bar" as foo;
+    `,
+      description: "Different namespace"
+    },
+    {
+      code: `
+      @use "sass:math" as *;
+    `,
+      description: "Without namespace"
+    },
+    {
+      code: `
+      @use "sass:math";
+    `,
+      description: "No explicit namespace"
+    }
+  ],
+
+  reject: [
+    {
+      code: `
+      @use "foo" as foo;
+    `,
+      line: 2,
+      column: 7,
+      message: messages.rejected,
+      description: "Without url"
+    },
+    {
+      code: `
+      @use "src/corners" as corners;
+    `,
+      line: 2,
+      column: 7,
+      message: messages.rejected,
+      description: "With url"
+    },
+    {
+      code: `
+      @use "sass:math" as math;
+    `,
+      line: 2,
+      column: 7,
+      message: messages.rejected,
+      description: "Built-in module"
+    },
+    {
+      code: `
+      @use "foo"   as   foo;
+    `,
+      line: 2,
+      column: 7,
+      message: messages.rejected,
+      description: "Without space"
+    },
+    {
+      code: `
+      @use "foo" as foo with ($baz: 1px);
+    `,
+      line: 2,
+      column: 7,
+      message: messages.rejected,
+      description: "Configured"
+    },
+    {
+      code: `
+      @use "sass:color" as color with (
+        $baz: 1px
+      );
+    `,
+      line: 2,
+      column: 7,
+      message: messages.rejected,
+      description: "Configured multiline"
+    }
+  ]
+});

src/rules/at-use-no-redundant-alias/index.js

@@ -0,0 +1,53 @@
+"use strict";
+
+const { utils } = require("stylelint");
+const namespace = require("../../utils/namespace");
+const ruleUrl = require("../../utils/ruleUrl");
+
+const ruleName = namespace("at-use-no-redundant-alias");
+
+const messages = utils.ruleMessages(ruleName, {
+  rejected: "Unnecessary explicit namespace"
+});
+
+const meta = {
+  url: ruleUrl(ruleName)
+};
+
+function getDefaultNamespace(module) {
+  return module.match(/([^/:]+)$/)[1].replace(/\.[^.]|["]+$/, "");
+}
+
+function separateEachParams(paramString) {
+  const parts = paramString.replace(/"/g, "").split(/\s+as\s+|\s+with\s+/);
+  if (parts.length < 2) return;
+  return parts;
+}
+
+function rule(actual) {
+  return (root, result) => {
+    const validOptions = utils.validateOptions(result, ruleName, { actual });
+
+    if (!validOptions) {
+      return;
+    }
+
+    root.walkAtRules("use", decl => {
+      const parts = separateEachParams(decl.params);
+      if (parts && getDefaultNamespace(parts[0]) === parts[1]) {
+        utils.report({
+          message: messages.rejected,
+          node: decl,
+          result,
+          ruleName
+        });
+      }
+    });
+  };
+}
+
+rule.ruleName = ruleName;
+rule.messages = messages;
+rule.meta = meta;
+
+module.exports = rule;

src/rules/index.js

@@ -23,6 +23,7 @@ const rules = {
   "at-mixin-pattern": require("./at-mixin-pattern"),
   "at-rule-conditional-no-parentheses": require("./at-rule-conditional-no-parentheses"),
   "at-rule-no-unknown": require("./at-rule-no-unknown"),
+  "at-use-no-redundant-alias": require("./at-use-no-redundant-alias"),
   "at-use-no-unnamespaced": require("./at-use-no-unnamespaced"),
   "comment-no-empty": require("./comment-no-empty"),
   "comment-no-loud": require("./comment-no-loud"),