Crate perseus_size_opt

This is a very simple plugin for Perseus that applies size optimizations automatically, which decrease the size of your final Wasm bundle significantly, meaning faster loads for users because a smaller amount of data needs to be transferred to their browsers. Because Perseus renders a page almost immediately through static generation, and then the Wasm bundle is needed to make that page interactive, applying this plugin will decrease your app’s time-to-interactive and its total blocking time (a Lighthouse metric that normal Perseus apps don’t do so well in on mobile).

If you’re new to Perseus, check it out on it’s website and on GitHub! Basically though, it’s a really fast and fully-featured web framework for Rust!

Usage

In your src/lib.rs, add the following to the bottom of the define_app! macro:

plugins: Plugins::new().plugin(perseus_size_opt(), SizeOpts::default())

If you have any other plugins defined, add the .plugin() call where appropriate. You’ll also need to add the following imports:

use perseus_size_opt::{perseus_size_opt, SizeOpts};

Once that’s done, run perseus tinker to apply the optimizations (this needs a separate command because they involve modifying the .perseus/ directory), and then you can work with your app as normal!

If you ever want to uninstall the plugin, just remove the relevant .plugin() call and re-run perseus tinker, and it’ll be completely removed.

Optimizations

This plugin currently performs the following optimizations:

• wee_alloc – an alternative allocator designed for Wasm that reduces binary size at the expense of slightly slower allocations
• lto – reduces binary size when set to true by enabling link-time optimizations
• opt-level – optimizes aggressively for binary size when set to z
• codegen-units – makes faster and smaller code when set to lower values (but makes compile times slower in release mode)

Note that all optimizations will only apply to release builds. except for the use of wee_alloc, which will also affect development builds.

Options

There are a few defaults available for setting size optimization levels, or you can build your own custom settings easily by constructing SizeOpts manually.

• ::default() – enables all optimizations
• ::default_no_lto() – enables all optimizations except lto = true, because that can break compilation of execution on some hosting providers, like Netlify.
• ::only_wee_alloc() – only uses wee_alloc, applying no other optimizations
• ::no_wee_alloc() – applies all optimizations other than wee_alloc

Stability

This plugin is considered quite stable due to how basic its optimizations are (the whole thing is one file), and so its stability is mostly dependent on that of Perseus. If you’re happy to use Perseus, you shouldn’t need to worry about using this plugin as well (in fact, it’s recommended that all Perseus apps use this plugin).

Structs

SizeOpts

Options for size optimizations. Note that these settings will only affect release builds (e.g. when you run perseus deploy), not development builds (except using wee_alloc, whcih will affect everything).

Enums

Error

The errors that this plugin can return.

Functions

perseus_size_opt

Gets the plugin itself to be handed to Perseus’ define_app! macro. Note that this plugin’s optimizations will only take effect in release mode (e.g. when you run perseus deploy).