no-redundant-roles rule

Author: kddnewton

README.md

@@ -67,7 +67,7 @@ I'm currently working on getting parity between this project and `eslint-plugin-
 - [x] no-autofocus
 - [x] no-distracting-elements
 - [ ] no-onchange
-- [ ] no-redundant-roles
+- [x] no-redundant-roles
 - [ ] role-has-required-aria-props
 - [x] tabindex-no-positive
 

docs/rules/no-redundant-roles.md

@@ -0,0 +1,34 @@
+# no-redundant-roles
+
+Some HTML elements have native semantics that are implemented by the browser. This includes default/implicit ARIA roles. Setting an ARIA role that matches its default/implicit role is redundant since it is already set by the browser.
+
+_References:_
+
+1. [W3](https://www.w3.org/TR/html5/dom.html#aria-role-attribute)
+
+## Rule details
+
+The default options for this rule allow an implicit role of `navigation` to be applied to a `nav` element as is [advised by W3](https://www.w3.org/WAI/GL/wiki/Using_HTML5_nav_element#Example:The_.3Cnav.3E_element). The options are provided as an object keyed by HTML element name; the value is an array of implicit ARIA roles that are allowed on the specified element.
+
+```json
+{
+  "jsx-a11y/no-redundant-roles": ["error", {
+    "nav": ["navigation"]
+  }
+}
+```
+
+### Succeed
+
+```vue
+<div />
+<button role="presentation" />
+```
+
+### Fail
+
+<!-- eslint-ignore -->
+
+```vue
+<button role="button" /> <img role="img" src="foo.jpg" />
+```

package.json

@@ -18,6 +18,7 @@
   },
   "devDependencies": {
     "eslint": "^6.8.0",
+    "eslint-plugin-vue-a11y": "^0.0.31",
     "husky": "^4.2.5",
     "jest": "^25.4.0",
     "prettier": "^2.0.5",

src/rules/__tests__/no-redundant-roles.test.js

@@ -0,0 +1,20 @@
+const rule = require("../no-redundant-roles");
+const makeRuleTester = require("./makeRuleTester");
+
+makeRuleTester("no-redundant-roles", rule, {
+  valid: ["<a role='link' />", "<div role='link' />"],
+  invalid: [
+    {
+      code: '<template><img role="img" src="foo.jpg" /></template>',
+      errors: [{ message: rule.makeMessage("img", "img") }]
+    },
+    {
+      code: '<template><a role="link" href="#" /></template>',
+      errors: [{ message: rule.makeMessage("a", "link") }]
+    },
+    {
+      code: '<template><button role="button" /></template>',
+      errors: [{ message: rule.makeMessage("button", "button") }]
+    }
+  ]
+});

src/rules/aria-role.js

@@ -1,6 +1,7 @@
 const { dom, roles } = require("aria-query");
 const {
   defineTemplateBodyVisitor,
+  getAttributeValue,
   getElementType,
   isAttribute,
   makeDocsURL
@@ -9,24 +10,6 @@ const {
 const message =
   "Elements with ARIA roles must use a valid, non-abstract ARIA role.";
 
-const getAttributeValue = (node) => {
-  const { key, value } = node;
-
-  if (!value) {
-    return null;
-  }
-
-  if (!node.directive) {
-    return value.value;
-  }
-
-  if (key.name.name === "bind" && value.expression) {
-    return value.expression.value;
-  }
-
-  return null;
-};
-
 module.exports = {
   meta: {
     docs: {

src/rules/no-redundant-roles.js

@@ -0,0 +1,95 @@
+const { elementRoles } = require("aria-query");
+const {
+  defineTemplateBodyVisitor,
+  getElementAttributeValue,
+  getElementType,
+  makeDocsURL
+} = require("../utils");
+
+const exceptions = { nav: ["navigation"] };
+const makeMessage = (type, role) => `\
+The element ${type} has an implicit role of ${role}. Defining this \
+explicitly is redundant and should be avoided.`;
+
+const hasRoleAttributes = (node, attributes) =>
+  attributes.every((attribute) => {
+    const value = getElementAttributeValue(node, attribute.name);
+
+    if (attribute.value) {
+      return value === attribute.value;
+    }
+
+    if (attribute.constraints) {
+      switch (attribute.constraints[0]) {
+        case "set":
+          return value;
+        case "undefined":
+          return !value;
+        default:
+          return null;
+      }
+    }
+
+    return value;
+  });
+
+const getImplicitRoleSet = (node) => {
+  const elementType = getElementType(node);
+
+  for (const [key, value] of elementRoles) {
+    if (key.name === elementType) {
+      if (!key.attributes || hasRoleAttributes(node, key.attributes)) {
+        return value;
+      }
+    }
+  }
+  return null;
+};
+
+module.exports = {
+  getImplicitRoleSet,
+  meta: {
+    docs: {
+      url: makeDocsURL("no-redundant-roles")
+    },
+    schema: [
+      {
+        type: "object",
+        additionalProperties: {
+          type: "array",
+          items: {
+            type: "string"
+          },
+          uniqueItems: true
+        }
+      }
+    ]
+  },
+  create(context) {
+    return defineTemplateBodyVisitor(context, {
+      VElement(node) {
+        const type = getElementType(node);
+        const implicitRoleSet = getImplicitRoleSet(node);
+        const explicitRole = getElementAttributeValue(node, "role");
+
+        if (!implicitRoleSet || !explicitRole) {
+          return;
+        }
+
+        const permittedRoles = context.options[0] || {};
+        if (
+          (permittedRoles[type] || [])
+            .concat(exceptions[type] || [])
+            .includes(explicitRole)
+        ) {
+          return;
+        }
+
+        if (implicitRoleSet.has(explicitRole)) {
+          context.report({ node, message: makeMessage(type, explicitRole) });
+        }
+      }
+    });
+  },
+  makeMessage
+};

src/utils.js

@@ -1,4 +1,7 @@
 const defineTemplateBodyVisitor = require("./utils/defineTemplateBodyVisitor");
+const getAttributeValue = require("./utils/getAttributeValue");
+const getElementAttribute = require("./utils/getElementAttribute");
+const getElementAttributeValue = require("./utils/getElementAttributeValue");
 const hasContent = require("./utils/hasContent");
 const isAttribute = require("./utils/isAttribute");
 const makeDocsURL = require("./utils/makeDocsURL");
@@ -44,6 +47,9 @@ const isAttributeWithValue = (node, name) => {
 
 module.exports = {
   defineTemplateBodyVisitor,
+  getAttributeValue,
+  getElementAttribute,
+  getElementAttributeValue,
   getElementType,
   getLiteralAttributeValue,
   hasContent,

src/utils/getAttributeValue.js

@@ -0,0 +1,19 @@
+const getAttributeValue = (node) => {
+  const { key, value } = node;
+
+  if (!value) {
+    return null;
+  }
+
+  if (!node.directive) {
+    return value.value;
+  }
+
+  if (key.name.name === "bind" && value.expression) {
+    return value.type === "Literal" ? value.expression.value : value.expression;
+  }
+
+  return null;
+};
+
+module.exports = getAttributeValue;

src/utils/getElementAttribute.js

@@ -0,0 +1,18 @@
+const getElementAttribute = (node, name) => {
+  for (const attribute of node.startTag.attributes) {
+    const { key } = attribute;
+
+    if (
+      (!attribute.directive && key.name === name) ||
+      (attribute.directive &&
+        key.name.name === "bind" &&
+        key.argument.name === name)
+    ) {
+      return attribute;
+    }
+  }
+
+  return null;
+};
+
+module.exports = getElementAttribute;

src/utils/getElementAttributeValue.js

@@ -0,0 +1,9 @@
+const getAttributeValue = require("./getAttributeValue");
+const getElementAttribute = require("./getElementAttribute");
+
+const getElementAttributeValue = (node, name) => {
+  const attribute = getElementAttribute(node, name);
+  return attribute && getAttributeValue(attribute);
+};
+
+module.exports = getElementAttributeValue;

src/utils/hasContent.js

@@ -1,30 +1,7 @@
-const getAttributeValue = (node, name) => {
-  for (const attribute of node.startTag.attributes) {
-    const { key, value } = attribute;
-
-    if (!value) {
-      continue;
-    }
-
-    if (!attribute.directive && key.name === name) {
-      return value.value;
-    }
-
-    if (
-      attribute.directive &&
-      key.name.name === "bind" &&
-      key.argument.name === name &&
-      value.expression
-    ) {
-      return value.expression.value;
-    }
-  }
-
-  return null;
-};
+const getElementAttributeValue = require("./getElementAttributeValue");
 
 const isHiddenFromScreenReader = (node) => {
-  const ariaHidden = getAttributeValue(node, "aria-hidden");
+  const ariaHidden = getElementAttributeValue(node, "aria-hidden");
   return ariaHidden && ariaHidden.toString() === "true";
 };