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repl: fix cpu overhead pasting big strings to the REPL #59857

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Merged
nodejs-github-bot merged 1 commit into from
Sep 14, 2025
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repl: fix cpu overhead pasting big strings to the REPL #59857

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repl: fix cpu overhead pasting big strings to the REPL 
Pasting input should not trigger any completions and other
calculations. This is now handled by just writing the string to the
terminal in case the user is pasting. As soon as pasting is done,
the completions will be re-enabled.

Fixes: #40626
Fixes: #43343
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@BridgeAR
BridgeAR committed Sep 11, 2025
commit 7bcf0bc31cd1a7960d97e42431a1d8bccce717d3
6 changes: 6 additions & 0 deletions lib/internal/readline/interface.js
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Original file line number Diff line number Diff line change
Expand Up @@ -658,6 +658,12 @@ class Interface extends InterfaceConstructor {

[kInsertString](c) {
this[kBeforeEdit](this.line, this.cursor);
if (!this.isCompletionEnabled) {
this.line += c;
this.cursor += c.length;
this[kWriteToOutput](c);
return;
}
if (this.cursor < this.line.length) {
const beg = StringPrototypeSlice(this.line, 0, this.cursor);
const end = StringPrototypeSlice(
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36 changes: 36 additions & 0 deletions test/parallel/test-repl-paste-big-data.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
'use strict';

const common = require('../common');
const repl = require('repl');
const stream = require('stream');
const assert = require('assert');

// Pasting big input should not cause the process to have a huge CPU usage.

const cpuUsage = process.cpuUsage();

const r = initRepl();
r.input.emit('data', 'a'.repeat(2e4) + '\n');
r.input.emit('data', '.exit\n');

r.once('exit', common.mustCall(() => {
const diff = process.cpuUsage(cpuUsage);
assert.ok(diff.user < 1e6);
}));

function initRepl() {
const input = new stream();
input.write = input.pause = input.resume = () => {};
input.readable = true;

const output = new stream();
output.write = () => {};
output.writable = true;

return repl.start({
input,
output,
terminal: true,
prompt: ''
});
}
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