add eslint rule

Author: Lms24

packages/eslint-config-sdk/src/index.js

@@ -143,7 +143,10 @@ module.exports = {
           },
         ],
 
+        // We want to prevent optional chaining & nullish coalescing usage in our files
+        // to prevent uncessary bundle size. Turned off in tests.
         '@sentry-internal/sdk/no-optional-chaining': 'error',
+        '@sentry-internal/sdk/no-nullish-coalescing': 'error',
 
         // JSDOC comments are required for classes and methods. As we have a public facing codebase, documentation,
         // even if it may seems excessive at times, is important to emphasize. Turned off in tests.
@@ -177,6 +180,7 @@ module.exports = {
         '@typescript-eslint/no-non-null-assertion': 'off',
         '@typescript-eslint/no-empty-function': 'off',
         '@sentry-internal/sdk/no-optional-chaining': 'off',
+        '@sentry-internal/sdk/no-nullish-coalescing': 'off',
       },
     },
     {

packages/eslint-plugin-sdk/src/index.js

@@ -11,6 +11,7 @@
 module.exports = {
   rules: {
     'no-optional-chaining': require('./rules/no-optional-chaining'),
+    'no-nullish-coalescing': require('./rules/no-nullish-coalescing'),
     'no-eq-empty': require('./rules/no-eq-empty'),
   },
 };

packages/eslint-plugin-sdk/src/rules/no-nullish-coalescing.js

@@ -0,0 +1,48 @@
+/**
+ * @fileoverview disallow nullish coalescing operators as they were introduced only in ES2020 and hence require
+ * us to add a polyfill. This increases bundle size more than avoiding nullish coalescing operators all together.
+ *
+ * @author Lukas Stracke
+ *
+ * Based on: https://github.com/mysticatea/eslint-plugin-es/blob/v4.1.0/lib/rules/no-nullish-coalescing-operators.js
+ */
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow nullish coalescing operators.',
+      category: 'Best Practices',
+      recommended: true,
+    },
+    messages: {
+      forbidden: 'Avoid using nullish coalescing operators.',
+    },
+    fixable: null,
+    schema: [],
+  },
+  create(context) {
+    return {
+      "LogicalExpression[operator='??']"(node) {
+        context.report({
+          node: context.getSourceCode().getTokenAfter(node.left, isNullishCoalescingOperator),
+          messageId: 'forbidden',
+        });
+      },
+    };
+  },
+};
+
+/**
+ * Checks if the given token is a nullish coalescing operator or not.
+ * @param {Token} token - The token to check.
+ * @returns {boolean} `true` if the token is a nullish coalescing operator.
+ */
+function isNullishCoalescingOperator(token) {
+  return token.value === '??' && token.type === 'Punctuator';
+}

packages/node/.eslintrc.js

@@ -5,5 +5,6 @@ module.exports = {
   extends: ['../../.eslintrc.js'],
   rules: {
     '@sentry-internal/sdk/no-optional-chaining': 'off',
+    '@sentry-internal/sdk/no-nullish-coalescing': 'off',
   },
 };