chore: enable prefer-nullish-coalescing internally (#7955)

* chore: enable prefer-nullish-calescing internally

* A couple complaints

* One last complaint

* Enable ignoreConditionalTests

Author: JoshuaKGoldberg

.eslintrc.js

@@ -51,9 +51,6 @@ module.exports = {
     // make sure we're not leveraging any deprecated APIs
     'deprecation/deprecation': 'error',
 
-    // TODO(#7338): Investigate enabling these soon ✨
-    '@typescript-eslint/prefer-nullish-coalescing': 'off',
-
     // TODO(#7130): Investigate changing these in or removing these from presets
     '@typescript-eslint/no-confusing-void-expression': 'off',
     '@typescript-eslint/prefer-string-starts-ends-with': 'off',
@@ -109,6 +106,13 @@ module.exports = {
       'error',
       { varsIgnorePattern: '^_', argsIgnorePattern: '^_' },
     ],
+    '@typescript-eslint/prefer-nullish-coalescing': [
+      'error',
+      {
+        ignoreConditionalTests: true,
+        ignorePrimitives: true,
+      },
+    ],
 
     //
     // Internal repo rules

packages/eslint-plugin/src/rules/padding-line-between-statements.ts

@@ -476,7 +476,7 @@ function verifyForAlways(
             }
             return true;
           },
-        }) || nextNode;
+        }) ?? nextNode;
       const insertText = isTokenOnSameLine(prevToken, nextToken)
         ? '\n\n'
         : '\n';

packages/eslint-plugin/src/rules/unified-signatures.ts

@@ -369,7 +369,7 @@ export default createRule<Options, MessageIds>({
         }
 
         return typeContainsTypeParameter(
-          (type as Partial<TSESTree.TSTypeAnnotation>).typeAnnotation ||
+          (type as Partial<TSESTree.TSTypeAnnotation>).typeAnnotation ??
             (type as TSESTree.TSArrayType).elementType,
         );
       }
@@ -523,7 +523,7 @@ export default createRule<Options, MessageIds>({
       key ??= getOverloadKey(signature);
       if (
         currentScope &&
-        (containingNode || signature).parent === currentScope.parent
+        (containingNode ?? signature).parent === currentScope.parent
       ) {
         const overloads = currentScope.overloads.get(key);
         if (overloads !== undefined) {

packages/rule-tester/src/utils/getRuleOptionsSchema.ts

@@ -33,5 +33,5 @@ export function getRuleOptionsSchema(
   }
 
   // Given a full schema, leave it alone
-  return schema || null;
+  return schema ?? null;
 }