feat: custom plugin

packages/eslint-plugin-antfu/src/index.ts

@@ -0,0 +1,7 @@
+import noLeadingNewline from './rules/no-leading-newline'
+
+export default {
+  rules: {
+    'no-leading-newline': noLeadingNewline,
+  },
+}

packages/eslint-plugin-antfu/src/rules/no-leading-newline.ts

@@ -0,0 +1,44 @@
+import { createEslintRule } from '../utils'
+
+export const RULE_NAME = 'no-leading-newline'
+export type MessageIds = 'noLeadingNewline'
+export type Options = []
+
+export default createEslintRule<Options, MessageIds>({
+  name: RULE_NAME,
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'Do not allow leading newline',
+      recommended: 'error',
+    },
+    fixable: 'whitespace',
+    schema: [],
+    messages: {
+      noLeadingNewline: 'No leading newline allowed',
+    },
+  },
+  defaultOptions: [],
+  create: (context) => {
+    return {
+      Program(node) {
+        const code = context.getSourceCode()
+        const match = code.text.match(/^[\s]+/)?.[0] || ''
+        if (match.includes('\n')) {
+          const line = match.split('\n')
+          context.report({
+            node,
+            loc: {
+              start: { line: 0, column: 0 },
+              end: { line: line.length - 1, column: line[line.length - 1].length },
+            },
+            messageId: 'noLeadingNewline',
+            fix(fixer) {
+              return fixer.replaceTextRange([0, match.length], '')
+            },
+          })
+        }
+      },
+    }
+  },
+})

packages/eslint-plugin-antfu/src/utils.ts

@@ -0,0 +1,5 @@
+import { ESLintUtils } from '@typescript-eslint/utils'
+
+export const createEslintRule = ESLintUtils.RuleCreator(
+  ruleName => ruleName,
+)