Add rule @typescript-eslint/prefer-nullish-coalescing

Author: Shinigami92

.eslintrc.js

@@ -104,6 +104,7 @@ module.exports = defineConfig({
           'multiline',
           'nashorn',
           'nocheck',
+          'nullish',
           'phantomjs',
           'pragma',
           'prototypejs',

src/rules/typescript-eslint/index.d.ts

@@ -7,6 +7,7 @@ import type { NoInferrableTypesRule } from './no-inferrable-types';
 import type { NoParameterPropertiesRule } from './no-parameter-properties';
 import type { NoUnsafeAssignmentRule } from './no-unsafe-assignment';
 import type { NoUnusedVarsRule } from './no-unused-vars';
+import type { PreferNullishCoalescingRule } from './prefer-nullish-coalescing';
 
 /**
  * All @typescript-eslint rules.
@@ -19,4 +20,5 @@ export type TypeScriptEslintRules = BanTsCommentRule &
   NoInferrableTypesRule &
   NoParameterPropertiesRule &
   NoUnsafeAssignmentRule &
-  NoUnusedVarsRule;
+  NoUnusedVarsRule &
+  PreferNullishCoalescingRule;

src/rules/typescript-eslint/prefer-nullish-coalescing.d.ts

@@ -0,0 +1,49 @@
+import type { RuleConfig } from '../rule-config';
+
+/**
+ * Option.
+ */
+export type PreferNullishCoalescingOption = {
+  /**
+   * Setting this option to `true` (the default) will cause the rule to ignore any cases that are located within a conditional test.
+   *
+   * @default true
+   *
+   * @see [ignoreConditionalTests](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.md#ignoreconditionaltests)
+   */
+  ignoreConditionalTests?: boolean;
+  /**
+   * Setting this option to `true` (the default) will cause the rule to ignore any logical or expressions that are part of a mixed logical expression (with `&&`).
+   *
+   * @default true
+   *
+   * @see [ignoreMixedLogicalExpressions](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.md#ignoremixedlogicalexpressions)
+   */
+  ignoreMixedLogicalExpressions?: boolean;
+};
+
+/**
+ * Options.
+ */
+export type PreferNullishCoalescingOptions = [PreferNullishCoalescingOption?];
+
+/**
+ * Enforce the usage of the nullish coalescing operator instead of logical chaining.
+ *
+ * @see [prefer-nullish-coalescing](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.md)
+ */
+export type PreferNullishCoalescingRuleConfig = RuleConfig<PreferNullishCoalescingOptions>;
+
+/**
+ * Enforce the usage of the nullish coalescing operator instead of logical chaining.
+ *
+ * @see [prefer-nullish-coalescing](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.md)
+ */
+export interface PreferNullishCoalescingRule {
+  /**
+   * Enforce the usage of the nullish coalescing operator instead of logical chaining.
+   *
+   * @see [prefer-nullish-coalescing](https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-nullish-coalescing.md)
+   */
+  '@typescript-eslint/prefer-nullish-coalescing': PreferNullishCoalescingRuleConfig;
+}