Annotate javascript constants as pure

[hadeeb]

This lets the Javascript minifiers remove these constants from the final bundle

[lpil]

When I tested this it didn't make any difference. Did you verify it working?

[hadeeb]

When I bundle the generated js code with esbuild, it pulls the globally defined constants.

esbuild build/dev/javascript/app/app.mjs --bundle --format=esm --target=node20

Generated output

import gleam/io
import gleam/string

pub fn main() {
  "Hello, Gleam!" |> string.lowercase |> io.println
}

// build/dev/javascript/gleam_stdlib/dict.mjs
var tempDataView = new DataView(new ArrayBuffer(8));
var SHIFT = 5;
var BUCKET_SIZE = Math.pow(2, SHIFT);
var MASK = BUCKET_SIZE - 1;
var MAX_INDEX_NODE = BUCKET_SIZE / 2;
var MIN_ARRAY_NODE = BUCKET_SIZE / 4;
var unequalDictSymbol = Symbol();

// build/dev/javascript/gleam_stdlib/gleam_stdlib.mjs
function lowercase(string) {
    return string.toLowerCase();
}
var unicode_whitespaces = [
    " ",
    // Space
    "	",
    // Horizontal tab
    "\n",
    // Line feed
    "\v",
    // Vertical tab
    "\f",
    // Form feed
    "\r",
    // Carriage return
    "\x85",
    // Next line
    "\u2028",
    // Line separator
    "\u2029",
    // Paragraph separator
].join("");
var trim_start_regex = new RegExp(`^[${unicode_whitespaces}]*`);
var trim_end_regex = new RegExp(`[${unicode_whitespaces}]*$`);
function console_log(term) {
    console.log(term);
}

// build/dev/javascript/app/app.mjs
function main() {
    let _pipe = "Hello, Gleam!";
    let _pipe$1 = lowercase(_pipe);
    return console_log(_pipe$1);
}
export { main };

Running terser or swc on this js bundle does not remove the constants, unless annotated as PURE.

SWC Playground

With Annotations

Rollup (and Vite, by extension) does not seem to import these unrelated constants.
Also, I am not sure how common the bundle with esbuild => run the minifier workflow is.

[lpil]

Great! Thank you for that. Glad it's working now