README.md

fs-existssync-valid-args

This codemod validates and converts invalid argument types to fs.existsSync(). It's useful to migrate code that passes invalid argument types which now causes deprecation warnings or errors.

Description

Starting with Node.js, passing invalid argument types to fs.existsSync() triggers a deprecation warning (DEP0187). The function should only receive string, Buffer, or URL arguments as documented in the Node.js fs.existsSync() documentation.

This codemod automatically:

• Validates that fs.existsSync() receives valid argument types
• Converts invalid argument types to valid ones where possible
• Handles both CommonJS (require) and ESM (import) syntax
• Adds type checks or conversions to ensure argument validity

Examples

Case 1: Direct Literal Values

Before:

const fs = require("node:fs");

const exists = fs.existsSync(123);

After:

const fs = require("node:fs");

const exists = fs.existsSync(String(123));

Case 2: Variable Arguments

Before:

const fs = require("node:fs");

function checkFile(path) {
  return fs.existsSync(path);
}

After:

const fs = require("node:fs");

function checkFile(path) {
  if (typeof path !== 'string' && !Buffer.isBuffer(path) && !(path instanceof URL)) {
    path = String(path);
  }
  return fs.existsSync(path);
}

Case 3: Null Values

Before:

const fs = require("node:fs");

const fileExists = fs.existsSync(null);

After:

const fs = require("node:fs");

const fileExists = fs.existsSync(String(null || ''));

Case 4: Object Arguments

Before:

import { existsSync } from "node:fs";

const exists = existsSync({ path: '/some/file' });

After:

import { existsSync } from "node:fs";

const exists = existsSync(String({ path: '/some/file' }));