`readline` Regression since v24.2.0 `Cannot read properties of undefined (reading 'pause')`

[robhogan]

Version

v24.13.0

Platform

Darwin robhogan-mac 25.1.0 Darwin Kernel Version 25.1.0: Mon Oct 20 19:34:05 PDT 2025; root:xnu-12377.41.6~2/RELEASE_ARM64_T6041 arm64

Subsystem

readline

What steps will reproduce the bug?

// readline-repro.js
const readline = require('readline');
const {Readable} = require('stream');

const input = Readable.from([]);
input.onHistoryFileLoaded = () => 'oops';
readline.createInterface(input);

node ./readline-repro.js

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior? Why is that the expected behavior?

Prior to Node v24.2.0, this did not crash

What do you see instead?

node readline-repro.js
node:internal/readline/interface:571
    this.input.pause();
               ^

TypeError: Cannot read properties of undefined (reading 'pause')
    at Interface.pause (node:internal/readline/interface:571:16)
    at ReplHistory.initialize (node:internal/repl/history:111:20)
    at Interface.setupHistoryManager (node:internal/readline/interface:392:27)
    at Interface.InterfaceConstructor (node:internal/readline/interface:218:8)
    at new Interface (node:readline:115:3)
    at Object.createInterface (node:readline:212:10)
    at Object.<anonymous> (/private/tmp/readline-repro.js:6:21)
    at Module._compile (node:internal/modules/cjs/loader:1734:14)
    at Object..js (node:internal/modules/cjs/loader:1899:10)
    at Module.load (node:internal/modules/cjs/loader:1469:32)

Node.js v24.2.0

Additional information

The example is contrived (what are we doing assigning onHistoryFileLoaded anyway?) but we hit this in the wild in a Node.js update when passing jest.mock() as the input. Rightly or wrongly, jest-mock by default uses a proxy object to create properties as mock functions on access.

So a more real-world issue would be:

// readline-test.js
const readline = require('readline');
readline.createInterface(jest.mock());

Now crashes.

I root caused this to #58225. Repeating here:

setupHistoryManager is called within InterfaceConstructor, here:

node/lib/internal/readline/interface.js

Line 218 in 644ba1f

this.setupHistoryManager(input);

Note that's before this.input is assigned, here:

node/lib/internal/readline/interface.js

Line 236 in 644ba1f

this.input = input;

Which is a problem because setupHistoryManager may call initialize()

node/lib/internal/readline/interface.js

Lines 384 to 389 in 644ba1f

	setupHistoryManager(options) {
	this.historyManager = new ReplHistory(this, options);
	if (options.onHistoryFileLoaded) {
	this.historyManager.initialize(options.onHistoryFileLoaded);
	}

Which tries to call .pause() on the interface's input property (still before it has been assigned)

node/lib/internal/repl/history.js

Line 111 in 644ba1f

this[kContext].pause();

CC @puskin

[Zohaibarif69]

I’m working on a fix that reorders the initialization so this.input is assigned before setupHistoryManager() runs, along with a regression test.
I’ll open a PR shortly.

[Zohaibarif69]

I’ve tried setting up a local environment, but due to network and build issues (see screenshot below), I won’t be able to continue testing locally right now. Leaving it for others to pick up.

![Terminal output showing network/download issue]

[github-actions]

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