✨ add es/no-export-ns-from rule (#36)

docs/rules/README.md

@@ -11,6 +11,7 @@ There is no config which enables all rules in this category.
 |:--------|:------------|:--:|
 | [es/no-bigint](./no-bigint.md) | disallow `bigint` syntax and built-ins. |  |
 | [es/no-dynamic-import](./no-dynamic-import.md) | disallow `import()` syntax. |  |
+| [es/no-export-ns-from](./no-export-ns-from.md) | disallow `export * as ns`. |  |
 | [es/no-global-this](./no-global-this.md) | disallow the `globalThis` variable. |  |
 | [es/no-import-meta](./no-import-meta.md) | disallow `new.target` meta property. |  |
 | [es/no-nullish-coalescing-operators](./no-nullish-coalescing-operators.md) | disallow nullish coalescing operators. |  |

docs/rules/no-export-ns-from.md

@@ -0,0 +1,16 @@
+# disallow `export * as ns` (es/no-export-ns-from)
+
+This rule reports ES2020 [`export * as ns`](https://github.com/tc39/proposal-export-ns-from) as errors.
+
+## Examples
+
+⛔ Examples of **incorrect** code for this rule:
+
+<eslint-playground type="bad" code="/*eslint es/no-export-ns-from: error */
+export * as ns from &quot;mod&quot;
+" />
+
+## 📚 References
+
+- [Rule source](https://github.com/mysticatea/eslint-plugin-es/blob/v3.0.1/lib/rules/no-export-ns-from.js)
+- [Test source](https://github.com/mysticatea/eslint-plugin-es/blob/v3.0.1/tests/lib/rules/no-export-ns-from.js)

lib/index.js

@@ -153,6 +153,7 @@ module.exports = {
         "no-destructuring": require("./rules/no-destructuring"),
         "no-dynamic-import": require("./rules/no-dynamic-import"),
         "no-exponential-operators": require("./rules/no-exponential-operators"),
+        "no-export-ns-from": require("./rules/no-export-ns-from"),
         "no-for-of-loops": require("./rules/no-for-of-loops"),
         "no-generators": require("./rules/no-generators"),
         "no-global-this": require("./rules/no-global-this"),

lib/rules/no-export-ns-from.js

@@ -0,0 +1,30 @@
+/**
+ * @author Yosuke Ota <https://github.com/ota-meshi>
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow `export * as ns`.",
+            category: "ES2020",
+            recommended: false,
+            url:
+                "http://mysticatea.github.io/eslint-plugin-es/rules/no-export-ns-from.html",
+        },
+        fixable: null,
+        messages: {
+            forbidden: "ES2020 'export * as ns' are forbidden.",
+        },
+        schema: [],
+        type: "problem",
+    },
+    create(context) {
+        return {
+            "ExportAllDeclaration[exported!=null]"(node) {
+                context.report({ node, messageId: "forbidden" })
+            },
+        }
+    },
+}

tests/lib/rules/no-export-ns-from.js

@@ -0,0 +1,35 @@
+/**
+ * @author Yosuke Ota <https://github.com/ota-meshi>
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+const RuleTester = require("../../tester")
+const rule = require("../../../lib/rules/no-export-ns-from.js")
+
+if (!RuleTester.isSupported(2020)) {
+    //eslint-disable-next-line no-console
+    console.log("Skip the tests of no-export-ns-from.")
+    return
+}
+
+new RuleTester({
+    parserOptions: { sourceType: "module" },
+}).run("no-export-ns-from", rule, {
+    valid: [
+        'export * from "mod"',
+        "export default foo",
+        'export {foo} from "mod"',
+        'export {foo as bar} from "mod"',
+        'import * as foo from "mod"',
+        'import foo from "mod"',
+        'import {foo} from "mod"',
+        'import {foo as bar} from "mod"',
+    ],
+    invalid: [
+        {
+            code: 'export * as ns from "mod"',
+            errors: ["ES2020 'export * as ns' are forbidden."],
+        },
+    ],
+})