Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Problem

I think the development option offers useful features, but I don’t think it’s good for a library to output different content based on an environment variable. I do think it’s useful for an integration to leverage a mode to determine what the output looks like.

• Webpack has mode. (This is already used)
• Vite has mode.
• Node.js has conditions.
• Rollup has no such option as far as I’m aware.
• ESBuild has no such option as far as I’m aware.

Especially when it comes to MDX on demand I believe it’s good to be explicit about this, because it determines whether the user should use /jsx-runtime or /jsx-dev-runtime.

Solution

• Default development to false, not process.env.NODE_ENV === 'development'
• @mdx-js/rollup: Support Vite env.mode
• @mdx-js/node-loader: Use the development exports condition in package.json to enable development mode.
• @mdx-js/register: Use the development exports condition in package.json to enable development mode.

This means Rollup, esbuild, and direct users of @mdx-js/mdx need to specify development: true explicitly.

Alternatives

Keep it as-is. 🤷