loading.md

How a script is loaded

goja, the JavaScript runtime (a pinned commit; direct dependency), has no modules. The loader (script.Load) therefore builds an executable script in four steps:

1. A header lexer finds the end of the imports and of the meta object literal.
2. meta is evaluated in a fresh runtime with no host globals, under the determinism stubs, and recorded as JSON.
3. Each imported helper is bundled by esbuild's Go API (a pinned release; direct dependency) with Bundle, Format IIFE, GlobalName __crw_lib_<n> and Target ES2017. The resolver plugin admits only the embedded crw:lib files and the script's workflows directory.
4. The body is wrapped as (async function __crw_main(){ const {a, b:c} = __crw_lib_<n>; ...body... }), syntax-checked and lowered with esbuild Transform (target ES2017), compiled by goja and called.

goja at the pinned commit runs ES2017 async functions, so the target is ES2017 and async/await are not lowered to generators (TestLoaderRunsMetaHelperAwaitReturn runs export const meta, a crw:lib import, a relative import, top-level await and top-level return in one file against that runtime). If a later pin stops passing that test, the target drops to ES2016 (esbuild then lowers async/await to generators) and this paragraph says so.