Option to generate ESM for standalone validators

What version of Ajv you are you using?

8.0.1

What problem do you want to solve?

Importing CommonJS modules creates non-ideal code when bundling with Rollup or Webpack and let them not participate in tree shaking. Code will be smaller and more efficient when ESM is used for bundling. This will also gain in importance as npm packages will soon ship more and more ESM code.

What do you think is the correct solution to problem?

There are two parts to be done here:

1. Add an esm option to ajv compile/standaloneCode
2. Ship ESM versions of the runtime files and have an exports map for Bundles and Node.js to pick them up correctly.

The first change is the more important one but both are necessary for the full effect.

Will you be able to implement it?

I’m not sure. I started looking through the code a bit and I see how to get started but I expect to get stuck at some point. I’d definitely need help down the line.

[realityking]

If anything, arguably, it is definitely more in scope of rollup or webpack to have better support for CommonJS that it is in scope of Ajv to generate ESM, but in any case another tool can be used.

Both Webpack and Rollup have invested a lot of time into this and it works from interoperability standpoint. It does however generate less optimal code (everything will be wrapped in a closure) and in the case of Webpack the module won’t participate in tree shaking.

ESM is the strictest of all the module formats as every export and import has to be static. This makes it easiest to transpile into any other module format. With both browsers and Node.js converging on it as the shared standard, I believe it’s where the future is heading. It’d be great to gain of some the benefits with standalone validators generated by AJV.

[kmoschcau]

I would also be interested in this. I am using AJV in an environment where I can’t easily add dependencies without shipping the entire dependency with my code. So the standalone code is already a really nice feature. However that environment only uses ESM, so currently I have to resort back to string replacement or similar. It would be great if AJV would have at least an option for the code generation to generate ESM instead of CommonJS.