I'm encountering a very strange issue. Perhaps @ludofischer from the cssnano project might have an idea as well.

I'm calling esbuild like so:

esbuild.build({
  entryPoints: ['src/app.tsx', 'src/app.css'],
  bundle: true,
  plugins: [postcss()],
  outdir: 'dist',
})

And my postcss.config.cjs reads as follows:

module.exports = {
  map: false,
  plugins: {
    'postcss-import': {},
    "tailwindcss/nesting": {},
    tailwindcss: {},
    autoprefixer: {},
    cssnano: { preset: 'default', },
  },
}

When I run npx postcss src/app.css directly, it prints minified CSS.

But when I run the esbuild.build function above (rm -rf dist && node esbuild.config.js && cat dist/app.css), it doesn't minify.

I tried commenting out the cssnano: { preset: 'default', } line to see if it makes any difference, and it turns out that cssnano does do some things, like combine border-width and border-color into a single border property. It just doesn't minify.

If you want to try and reproduce it, my code for this is at https://github.com/joliss/calculator.

I'm very confused as to why this might be happening.