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This recipe ensures REPL classes like REPLServer and Recoverable are properly instantiated with the new keyword.

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Deprecation

Node.js deprecated calling REPL constructors without the new keyword. Classes must be instantiated with new. See DEP0185 for more details.

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Usage

Run this codemod with: 
npx codemod nodejs/repl-classes-with-new

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Before/After

  const repl = require("node:repl");
  const { REPLServer, Recoverable } = require("node:repl");
  import { REPLServer } from "node:repl";
  const { REPLServer: REPL } = await import("node:repl");

  // Missing 'new' keyword
- const server1 = repl.REPLServer();
+ // With 'new' keyword
+ const server1 = new repl.REPLServer();
- const server2 = REPLServer({ prompt: ">>> " });
+ const server2 = new REPLServer({ prompt: ">>> " });
- const server3 = repl.Recoverable();
+ const server3 = new repl.Recoverable();
- const error = Recoverable(new SyntaxError());
+ const error = new Recoverable(new SyntaxError());
- const server4 = REPL({ prompt: ">>> " });
+ const server4 = new REPL({ prompt: ">>> " });

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What It Does

  • Adds new keyword before REPLServer() and Recoverable() calls
  • Works with both direct imports and namespace imports (e.g., repl.REPLServer())
  • Handles CommonJS and ESM module patterns
  • Supports aliased imports (e.g., REPLServer as REPL)

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Affected Classes

The following REPL classes are updated:
  • REPLServer - The main REPL server class
  • Recoverable - Error class for recoverable syntax errors

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Example Scenarios

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Creating a Custom REPL

  const repl = require('node:repl');

- const server = repl.REPLServer({
+ const server = new repl.REPLServer({
    prompt: 'my-repl> ',
    eval: customEval,
  });

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Handling Recoverable Errors

  const { Recoverable } = require('node:repl');

  function customEval(cmd, context, filename, callback) {
    try {
      const result = evaluate(cmd);
      callback(null, result);
    } catch (err) {
      if (isRecoverable(err)) {
-       callback(Recoverable(err));
+       callback(new Recoverable(err));
      } else {
        callback(err);
      }
    }
  }
Modern JavaScript requires all classes to be instantiated with the new keyword. This deprecation aligns Node.js REPL classes with standard JavaScript class syntax.

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