feat: add ssr config (#113)

* feat: add `ssr` config

* doc: add to README

* Update README.md

Co-authored-by: Pierre-Marie Dartus <p.dartus@salesforce.com>

* doc: add missing title

---------

Co-authored-by: Pierre-Marie Dartus <p.dartus@salesforce.com>

README.md

@@ -69,3 +69,21 @@ Add the `i18n` configuration to the `extends` field in your `.eslintrc` configur
     "extends": ["@salesforce/eslint-config-lwc/recommended", "@salesforce/eslint-config-lwc/i18n"]
 }
 ```
+
+### `@salesforce/eslint-config-lwc/ssr` configuration
+
+**Goal:**
+Promote writing server-side-rendering friendly components. We only recommend using this configuration if your components are running in experiences supporting LWC server-side-rendering.
+
+**Rules:**
+[ SSR specific rules ](https://github.com/salesforce/eslint-plugin-lwc/blob/master/README.md#lwc) only.
+
+**Usage:**
+
+Add the `ssr` configuration to the `extends` field in your `.eslintrc` configuration file, for example:
+
+```json
+{
+    "extends": ["@salesforce/eslint-config-lwc/recommended", "@salesforce/eslint-config-lwc/ssr"]
+}
+```

ssr.js

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2018, salesforce.com, inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+'use strict';
+
+module.exports = {
+    extends: [require.resolve('./lib/defaults')],
+    plugins: [
+        '@lwc/eslint-plugin-lwc', // https://github.com/salesforce/eslint-plugin-lwc
+    ],
+    rules: {
+        '@lwc/lwc/no-unsupported-ssr-properties': 'error',
+        '@lwc/lwc/no-restricted-browser-globals-during-ssr': 'error',
+    },
+};

test/ssr.js

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2021, salesforce.com, inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+'use strict';
+
+const assert = require('assert');
+const eslint = require('eslint');
+
+const { linkConfig, unlinkConfig } = require('./utils');
+
+describe('ssr configs', () => {
+    before(() => {
+        linkConfig();
+    });
+
+    after(() => {
+        unlinkConfig();
+    });
+
+    it('should load properly', async () => {
+        const cli = new eslint.ESLint({
+            useEslintrc: false,
+            baseConfig: {
+                extends: ['@salesforce/eslint-config-lwc/ssr'],
+            },
+        });
+
+        const results = await cli.lintText(`
+            import { LightningElement } from 'lwc';
+
+            export default class Foo extends LightningElement {
+              connectedCallback() {
+                document.write("Hello world")
+                this.dispatchEvent("Hello world")
+              }
+            }
+        `);
+
+        const { messages } = results[0];
+        assert.equal(messages.length, 2);
+        assert.equal(messages[0].ruleId, '@lwc/lwc/no-restricted-browser-globals-during-ssr');
+        assert.equal(messages[1].ruleId, '@lwc/lwc/no-unsupported-ssr-properties');
+    });
+});