warnOnce package in Refine source code.

In this article, we will review a package named warn-once. You will learn

1. What is warn-once?

2. Warn once usage in Refine source code

3. warn-once code review

What is warn-once?

Print a warning exactly once during development. Suitable for deprecation warnings, warnings for missing setup etc.

Installation

Run the below command in your CLI to install this package

npm install warn-once

Usage

warn-once accepts 2 parameters, one is the condition and the other one is the message that gets printed to the CLI exactly once. warn-once has some underlying checks to ensure this logs only once in the CLI.

const warnOnce = require('warn-once');

// ...

warnOnce(someCondition, 'This is a warning message');

Note: This warning is only shown only when NODE_ENV is not set to “production”

Warn once usage in Refine source code

So I found this package in the Refine codebase in a file named hooks/breadcrumbs/index.ts

if (action && action !== "list") {
    const key = `actions.${action}`;
    const actionLabel = translate(key);
    if (typeof i18nProvider !== "undefined" && actionLabel === key) {
      warnOnce(
        true,
        `[useBreadcrumb]: Breadcrumb missing translate key for the "${action}" action. Please add "actions.${action}" key to your translation file.\nFor more information, see https://refine.dev/docs/api-reference/core/hooks/useBreadcrumb/#i18n-support`,
      );
      breadcrumbs.push({
        label: translate(
          `buttons.${action}`,
          textTransformers.humanize(action),
        ),
      });
    } else {
      breadcrumbs.push({
        label: translate(key, textTransformers.humanize(action)),
      });
    }
  }

As you can see there are other files too, where this warn-once is used but with different parameters.

warn-once code review

index.js in the warn-once repository contains the below code

const DEV = process.env.NODE_ENV !== "production";

const warnings = new Set();

function warnOnce(condition, ...rest) {
  if (DEV && condition) {
    const key = rest.join(" ");

    if (warnings.has(key)) {
      return;
    }

    warnings.add(key);
    console.warn(...rest);
  }
}

module.exports = warnOnce;

I also happened to create a Pull request with an example demonstrating the ability to pass n number of message strings as parameters.

Set is used and has check ensures the message gets logged only once.

About me:

Hey, my name is Ramu Narasinga. I study large open-source projects and create content about their codebase architecture and best practices, sharing it through articles, videos.

I am open to work on interesting projects. Send me an email at ramu.narasinga@gmail.com

My Github — https://github.com/ramu-narasinga

My website — https://ramunarasinga.com

My Youtube channel — https://www.youtube.com/@thinkthroo

Learning platform — https://thinkthroo.com

Codebase Architecture — https://app.thinkthroo.com/architecture

Best practices — https://app.thinkthroo.com/best-practices

Production-grade projects — https://app.thinkthroo.com/production-grade-projects

References:

1. https://github.com/satya164/warn-once/pull/3

2. https://github.com/refinedev/refine/blob/main/packages/core/src/hooks/breadcrumb/index.ts#L109

3. https://www.npmjs.com/package/warn-once

4. https://github.com/satya164/warn-once/blob/main/index.js