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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
Merged

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

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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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