Minify embedded lib/**/*.js for lite builds

[davidfiala]

I'm looking at improvements to cut down on the size of light builds of node. A minimalistic static node with --v8-lite-mode and no intl comes in at 41,476 KB. YMMV as I've trimmed a few other things out already such as https://github.com/orgs/nodejs/discussions/53421.

I was wondering about the js files in lib and whether they could in theory be minified.

As an experiment, I used esbuild's minify flag on the directory without any other changes. It may or may not be safe, but it's just to start a conversation:

$ find lib -name '*.js' -exec sh -c 'mkdir -p "$(dirname "lib2/{}")" && esbuild "{}" --outfile="lib2/{}" --minify' \;

$ du -shk lib lib2
4304    lib
2616    lib2

...saving about 1,688 KB (39% drop) in JS changes alone.

Relative to the original, stripped node binary, that delta theoretically saves us 4% in final binary size.

One disadvantage I can think of is source mapping for console error traces. For embedded environments, the trade-off is probably worth it (for me personally, it definitely is). We can preserve debugging info by storing source maps as a separate build artifact.

Here's an example of artifact sizes if we split out source maps:

find lib -name '*.js' -exec sh -c 'mkdir -p "$(dirname "lib3/{}")" && esbuild "{}" --sourcemap=external --outfile="lib3/{}" --minify' \;
find lib3 -type f -name '*.js' -exec rm {} + # remove the generated JS, just keep the maps

$ du -shk lib lib2 lib3

4304    lib # original JS is 4.3M (what we ship today, bulking up the node binary)

2616    lib2 # minified JS is 2.6M (what we could be shipping instead)

6068    lib3 # source maps alone are 6M (preserved as a separate build artifact tied to every release)

I could imagine that such a minification could exist as a configure flag which triggers js2c (?) to behave differently.

What do folks think?

Thanks for your time!

[RedYetiDev]

Theoretically, I suppose they could be minified, but as I understand it, saving approximately 6MB isn’t a goal of the project. While there might be other projects that reduce the Node.js binary, 6MB is still 6MB, and with the normal binary, it's not that much space to save.

CC @nodejs/build to verify this.