Fix prettier integration being broken due to nullish coalescing misuse (#836)

Author: Simon Waiblinger

lib/xo-to-eslint.ts

@@ -81,7 +81,8 @@ export function xoToEslintConfig(flatXoConfig: XoConfigItem[] | undefined, {pret
 				baseConfig.push({...eslintConfigPrettier, files: eslintConfigItem.files});
 			} else {
 				// Validate that Prettier options match other `xoConfig` options.
-				if ((xoConfigItem.semicolon && prettierOptions.semi === false) ?? (!xoConfigItem.semicolon && prettierOptions.semi === true)) {
+				/* eslint-disable-next-line */
+				if ((xoConfigItem.semicolon && prettierOptions.semi === false) || (!xoConfigItem.semicolon && prettierOptions.semi === true)) {
 					throw new Error(`The Prettier config \`semi\` is ${prettierOptions.semi} while Xo \`semicolon\` is ${xoConfigItem.semicolon}, also check your .editorconfig for inconsistencies.`);
 				}
 

test/cli.test.ts

@@ -1195,3 +1195,20 @@ test('replaces cache file with directory when file exists at cache path', async
 	t.true(cachedFiles.some(file => file.startsWith('.cache')), 'ESLint cache should exist');
 });
 
+test('prettier validation detects semicolon conflicts', async t => {
+	const filePath = path.join(t.context.cwd, 'test.js');
+	await fs.writeFile(filePath, 'const x = true\n', 'utf8'); // No semicolon
+
+	// XO: no semicolons, Prettier: semicolons = conflict
+	const packageJson = {
+		xo: {
+			semicolon: false,
+			prettier: true,
+		},
+	};
+	await fs.writeFile(path.join(t.context.cwd, 'package.json'), JSON.stringify(packageJson), 'utf8');
+	await fs.writeFile(path.join(t.context.cwd, '.prettierrc'), '{"semi": true}', 'utf8');
+
+	const error = await t.throwsAsync($`node ./dist/cli --cwd ${t.context.cwd}`);
+	t.true(error.message.includes('semicolon'));
+});