feat: new if-newline rule

packages/eslint-plugin-antfu/src/rules/if-newline.test.ts

@@ -0,0 +1,30 @@
+import { RuleTester } from '@typescript-eslint/utils/dist/ts-eslint'
+import { it } from 'vitest'
+import rule, { RULE_NAME } from './if-newline'
+
+const valids = [
+  `if (true)
+  console.log('hello')
+`,
+  `if (true) {
+  console.log('hello')
+}`,
+]
+const invalids = [
+  ['if (true) console.log(\'hello\')', 'if (true) \nconsole.log(\'hello\')'],
+]
+
+it('runs', () => {
+  const ruleTester: RuleTester = new RuleTester({
+    parser: require.resolve('@typescript-eslint/parser'),
+  })
+
+  ruleTester.run(RULE_NAME, rule, {
+    valid: valids,
+    invalid: invalids.map(i => ({
+      code: i[0],
+      output: i[1],
+      errors: [{ messageId: 'missingIfNewline' }],
+    })),
+  })
+})