feat: add no-computed-public-class-fields rule

docs/no-computed-class-fields.md

@@ -0,0 +1,41 @@
+# no-computed-class-fields
+
+This prevents the use of computed properties as Class Fields
+
+```js
+const computed = 'bar'
+class Foo {
+  [computed] = 1
+}
+
+class Foo {
+  static [computed] = 1
+}
+```
+
+These will not be allowed because Chrome 72, while supporting class fields, does not support computed properties in class fields.
+
+## What is the Fix?
+
+Either make the property non-computed, or you can move these assignments to within the class constructor function for instance properties, or modify the class for static ones:
+
+```js
+const computed = 'bar'
+class Foo {
+  constructor() {
+    Object.defineProperty(this, computed, { configurable: true, enumerable: true, writable: true, value: 1 })
+  }
+}
+
+class Foo {
+  constructor() {
+    this[computed] = 1
+  }
+}
+
+// Static
+Object.defineProperty(Foo, computed, { configurable: true, enumerable: true, writable: true, value: 1 })
+Foo[computed] = 1
+```
+
+This can be safely disabled if you intend to compile code with the `@babel/plugin-proposal-class-properties` Babel plugin.

lib/index.js

@@ -49,6 +49,7 @@ createRule('no-optional-catch', 'edge > 0, safari > 0, firefox < 58, chrome < 66
 createRule('no-numeric-separators', 'edge > 0, safari < 13, firefox < 68, chrome < 75', 'disallow use of numeric seperators like 1_000_000')
 createRule('no-public-static-class-fields', 'edge > 0, safari > 0, firefox > 0, chrome < 72', 'disallow public static class fields like foo = 1')
 createRule('no-public-instance-class-fields', 'edge > 0, safari > 0, firefox < 69, chrome < 72', 'disallow public class fields like foo = 1')
+createRule('no-computed-public-static-class-fields', 'edge > 0, safari > 0, firefox < 69, chrome < 74', 'disallow computed public static or instance class fields like [foo] = 1')
 createRule('no-private-class-fields', 'edge > 0, safari > 0, firefox > 0, chrome < 74', 'disallow private class fields like #foo = 1')
 createRule('no-do-expression', 'edge > 0, safari > 0, firefox > 0, chrome > 0', 'disallow "do" expressions')
 createRule('no-bind-operator', 'edge > 0, safari > 0, firefox > 0, chrome > 0', 'disallow the :: bind operator')

lib/rules/no-computed-public-class-fields.js

@@ -0,0 +1,6 @@
+module.exports = (context, badBrowser) => ({
+  // Ignore type annotations that don't assign
+  'ClassProperty[computed=true]:not([typeAnnotation]:not([value]))'(node) {
+    context.report(node, `Computed Class Fields are not supported in ${badBrowser}`)
+  }
+})

test/no-computed-public-class-fields.js

@@ -0,0 +1,58 @@
+var rule = require('../lib/rules/no-computed-public-class-fields')
+var RuleTester = require('eslint').RuleTester
+
+var ruleTester = new RuleTester({parser: 'babel-eslint', parserOptions: {ecmaVersion: 2018}})
+
+ruleTester.run('no-public-class-fields', rule, {
+  valid: [
+    {code: 'class Foo { bar(){} }'}, 
+    {code: 'class Foo { static bar() {} }'},
+    {code: 'class Foo { bar: AType }'},
+    {code: 'class Foo { ["bar"]() {} }'},
+    {code: 'class Foo { static ["bar"]() {} }'},
+    {code: 'class Foo { static bar: AType }'},
+    {code: 'class Foo { static bar = () => {} }'},
+    {code: 'class Foo { static bar = 1 }'},
+    {code: 'class Foo { bar: AType }'},
+    {code: 'class Foo { bar = () => {} }'},
+    {code: 'class Foo { bar = 1 }'},
+  ],
+  invalid: [
+    {
+      code: 'class Foo { ["bar"] = () => {} }',
+      errors: [
+        {
+          message:
+            'Computed Class Fields are not supported in undefined'
+        }
+      ]
+    },
+    {
+      code: 'class Foo { ["bar"] = 1 }',
+      errors: [
+        {
+          message:
+          'Computed Class Fields are not supported in undefined'
+        }
+      ]
+    },
+    {
+      code: 'class Foo { static ["bar"] = () => {} }',
+      errors: [
+        {
+          message:
+            'Computed Class Fields are not supported in undefined'
+        }
+      ]
+    },
+    {
+      code: 'class Foo { static ["bar"] = 1 }',
+      errors: [
+        {
+          message:
+          'Computed Class Fields are not supported in undefined'
+        }
+      ]
+    }
+  ]
+})