Skip to content

Strange behavior with fs.watch on file with JSON stringified -> first update isn't emitted if too fast after fs.watch #53111

Description

@Apokalypt

Node.js Version

v18.17.1

NPM Version

9.6.7

Operating System

23.2.0 Darwin

Subsystem

fs

Description

I would like to watch changes on a file storing JSON stringified data but the watcher created with fs.watch is not emitted if the change happen to quickly after the call of fs.watch. The strange thing is that if the content is only a text (without JSON format) the watcher emit the event correctly...

Minimal Reproduction

const fs = require('fs');
const path = require('path');

const filePath = path.join(__dirname, 'test.json');
// Create the file if it doesn't exist
if (!fs.existsSync(filePath)) {
    fs.writeFileSync(filePath, "{ }");
}

fs.watch(filePath, (eventType, filename) => {
    console.log(`Event type is: ${eventType}`);
    if (filename) {
        console.log(`Filename provided: ${filename}`);
    } else {
        console.log('Filename not provided');
    }
});

fs.writeFileSync(filePath, "{ \"test\": \"test\", \"test2\": \"test2\" }"); // same with JSON.stringify(...)
// Listener above is called if we replace line above with:
// fs.writeFileSync(filePath, "very ok or not but I need a longer text to test something...");

Output

Expected

Event type is: change
Filename provided: test.json

Received

Nothing

Before You Submit

  • I have looked for issues that already exist before submitting this
  • My issue follows the guidelines in the README file, and follows the 'How to ask a good question' guide at https://stackoverflow.com/help/how-to-ask

Activity

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Metadata

Metadata

Assignees

No one assigned

    Labels

    confirmed-bugIssues and PRs for confirmed bugs.fsIssues and PRs related to file-system APIs and the fs module.macosIssues and PRs related to the macOS platform.

    Type

    No type

    Projects

    No projects

      Milestone

      No milestone

      Relationships

      None yet

      Development

      No branches or pull requests

      Issue actions