windows/runtime/src/napi_engine/module_runner.rs at main · NativeScript/windows

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//! ES modules for napi engines without a module loader reachable through their shim (QuickJS,

//! Hermes, JSC; Hermes can't parse `import`/`export` at all). Each module is transformed with oxc's

//! `ModuleRunnerTransform` (Vite's ssrTransform) into an async function whose imports, exports,

//! `import.meta` and `import()` go through runtime calls, and a JS module runner (`RUNNER`) keeps

//! the registry, links imports, resolves cycles and settles dynamic imports. Exports are getters,

//! hoisted above the imports, so live bindings hold through import cycles.

//!

//! Resolution, source loading (files, the sealed app.nsbundle, HTTP dev-server modules, the

//! `ns:module` builtin) and error text come from `crate::esm_loader`, as for the V8 engines, so a

//! graph resolves the same way on every engine. The engine supplies only its script evaluator.

//! Top-level await is supported (every module body is async); `import()` from a classic script is

//! not, since that syntax never reaches the transform.

use std::cell::Cell;

use napi::{sys, CallContext, Env, JsObject, JsUnknown, NapiRaw, NapiValue, Status, ValueType};

use crate::esm_loader;

/// Evaluate `code` as a classic script named `filename` and return its completion value. On

/// failure the engine's exception is left pending.

pub type EvalScript = fn(env: &Env, code: &str, filename: &str) -> Result<sys::napi_value, ()>;

thread_local! {

static EVAL: Cell<Option<EvalScript>> = const { Cell::new(None) };

}

/// The runner's module body parameters, in the order `RUNNER` passes them.

const WRAPPER_HEAD: &str = "(async function (__vite_ssr_exports__, __vite_ssr_import_meta__, \

__vite_ssr_import__, __vite_ssr_dynamic_import__, __vite_ssr_exportAll__, __vite_ssr_exportName__) \

{\"use strict\";\n";

const WRAPPER_TAIL: &str = "\n})";

/// A transformed module: the wrapper function's source and the specifiers it imports statically.

pub struct Transformed {

pub code: String,

pub deps: Vec<String>,

}

fn line_col(source: &str, offset: usize) -> (usize, usize) {

let before = &source[..offset.min(source.len())];

let line = before.matches('\n').count() + 1;

let col = before.rfind('\n').map_or(before.len(), |i| before.len() - i - 1) + 1;

(line, col)

}

/// Transform an ES module into the runner's async wrapper. `Err` carries a SyntaxError message

/// with the first error's location.

pub fn transform(source: &str, key: &str) -> Result<Transformed, String> {

use oxc::allocator::Allocator;

use oxc::codegen::Codegen;

use oxc::parser::Parser;

use oxc::semantic::SemanticBuilder;

use oxc::span::SourceType;

use oxc_transformer_plugins::ModuleRunnerTransform;

let allocator = Allocator::default();

let parsed = Parser::new(&allocator, source, SourceType::mjs()).parse();

if let Some(error) = parsed.diagnostics.first() {

let at = error

.labels

.as_ref()

.first()

.map(|label| line_col(source, label.offset() as usize));

return Err(match at {

Some((line, col)) => format!("{} ({key}:{line}:{col})", error.message),

None => format!("{} ({key})", error.message),

});

}

let mut program = parsed.program;

let scoping = SemanticBuilder::new().build(&program).semantic.into_scoping();

let (deps, _dynamic) = ModuleRunnerTransform::new().transform(&allocator, &mut program, scoping);

let body = Codegen::new().build(&program).code;

let mut deps: Vec<String> = deps.into_iter().collect();

deps.sort();

Ok(Transformed { code: format!("{WRAPPER_HEAD}{body}{WRAPPER_TAIL}"), deps })

}

fn arg_string(ctx: &CallContext, index: usize) -> napi::Result<Option<String>> {

if ctx.length <= index {

return Ok(None);

}

let v = ctx.get::<JsUnknown>(index)?;

if matches!(v.get_type()?, ValueType::Undefined | ValueType::Null) {

return Ok(None);

}

Ok(Some(v.coerce_to_string()?.into_utf8()?.as_str()?.to_owned()))

}

fn arg_strings(ctx: &CallContext, index: usize) -> napi::Result<Vec<String>> {

let mut out = Vec::new();

if ctx.length <= index {

return Ok(out);

}

let list = ctx.get::<JsUnknown>(index)?;

if !list.is_array()? {

return Ok(out);

}

let list: JsObject = unsafe { list.cast() };

for i in 0..list.get_array_length()? {

let item = list.get_element::<JsUnknown>(i)?;

out.push(item.coerce_to_string()?.into_utf8()?.as_str()?.to_owned());

}

Ok(out)

}

/// Throw a real `SyntaxError` (napi8 has no constructor for one) and return the pending marker.

fn throw_syntax_error(env: &Env, message: &str) -> napi::Error {

let thrown = (|| -> napi::Result<()> {

let ctor: napi::JsFunction = env.get_global()?.get_named_property("SyntaxError")?;

let error = ctor.new_instance(&[env.create_string(message)?])?;

env.throw(error)

})();

match thrown {

Ok(()) => napi::Error::new(Status::PendingException, String::new()),

Err(_) => napi::Error::from_reason(message.to_string()),

}

/// String coercion of the pending exception, cleared.

fn take_exception(env: &Env) -> String {

let mut exc: sys::napi_value = std::ptr::null_mut();

if unsafe { sys::napi_get_and_clear_last_exception(env.raw(), &mut exc) } != sys::Status::napi_ok

|| exc.is_null()

{

return "<no exception>".into();

}

unsafe { JsUnknown::from_raw_unchecked(env.raw(), exc) }

.coerce_to_string()

.and_then(|s| s.into_utf8())

.and_then(|s| Ok(s.as_str()?.to_owned()))

.unwrap_or_else(|_| "<unprintable exception>".into())

}

/// `__nsEsmLoad(key, spec, referrer) → { fn, deps }`: read, transform and evaluate a module's

/// wrapper. Throws the not-found reason, a SyntaxError, or the engine's own evaluation error.

fn load(ctx: CallContext) -> napi::Result<JsObject> {

let env = &ctx.env;

let key = arg_string(&ctx, 0)?.unwrap_or_default();

let Some(source) = esm_loader::read_source(&key) else {

let spec = arg_string(&ctx, 1)?.unwrap_or_else(|| key.clone());

let referrer = arg_string(&ctx, 2)?;

return Err(napi::Error::from_reason(esm_loader::not_found_message(

&spec,

referrer.as_deref(),

&key,

)));

};

let transformed = transform(&source, &key).map_err(|e| throw_syntax_error(env, &e))?;

let Some(eval) = EVAL.with(Cell::get) else {

return Err(napi::Error::from_reason("module runner is not installed"));

};

let function = eval(env, &transformed.code, &key)

.map_err(|()| napi::Error::new(Status::PendingException, String::new()))?;

let mut deps = env.create_array_with_length(transformed.deps.len())?;

for (i, dep) in transformed.deps.iter().enumerate() {

deps.set_element(i as u32, env.create_string(dep)?)?;

}

let mut out = env.create_object()?;

out.set_named_property("fn", unsafe { JsUnknown::from_raw_unchecked(env.raw(), function) })?;

out.set_named_property("deps", deps)?;

Ok(out)

}

/// Install the runner's natives and the runner itself, then `ns:module`'s natives over it. Call

/// after `host_abi::initialize_runtime` and before the shared prelude (which builds

/// `__nsModuleBuiltin` from `__nsModuleConfigureLoader`).

pub fn install(env: &Env, eval: EvalScript) -> napi::Result<()> {

EVAL.with(|e| e.set(Some(eval)));

let mut global = env.get_global()?;

crate::napi_engine::module_natives::install_script_compiler(env, eval)?;

let load_fn = env.create_function_from_closure("__nsEsmLoad", load)?;

global.set_named_property("__nsEsmLoad", load_fn)?;

let resolve = env.create_function_from_closure("__nsEsmResolve", |ctx: CallContext| {

let spec = arg_string(&ctx, 0)?.unwrap_or_default();

let referrer = arg_string(&ctx, 1)?;

ctx.env.create_string(&esm_loader::resolve(&spec, referrer.as_deref()))

})?;

global.set_named_property("__nsEsmResolve", resolve)?;

let prefetch = env.create_function_from_closure("__nsEsmPrefetch", |ctx: CallContext| {

esm_loader::prefetch(&arg_strings(&ctx, 0)?);

ctx.env.get_undefined()

})?;

global.set_named_property("__nsEsmPrefetch", prefetch)?;

let volatile = env.create_function_from_closure("__nsEsmIsVolatile", |ctx: CallContext| {

let key = arg_string(&ctx, 0)?.unwrap_or_default();

ctx.env.get_boolean(esm_loader::is_volatile(&key))

})?;

global.set_named_property("__nsEsmIsVolatile", volatile)?;

let registry_key = env.create_function_from_closure("__nsEsmRegistryKey", |ctx: CallContext| {

let url = arg_string(&ctx, 0)?.unwrap_or_default();

ctx.env.create_string(&esm_loader::registry_key_for(&url))

})?;

global.set_named_property("__nsEsmRegistryKey", registry_key)?;

// Registry keys the runner dropped: forget their load failures and prefetched bodies, and

// cache-bust the next fetch of each HTTP one.

let forget = env.create_function_from_closure("__nsEsmForget", |ctx: CallContext| {

let keys = arg_strings(&ctx, 0)?;

for key in &keys {

esm_loader::forget(key);

}

let http: Vec<String> = keys.into_iter().filter(|k| esm_loader::is_http(k)).collect();

esm_loader::mark_keys_for_cache_bust(&http);

ctx.env.get_undefined()

})?;

global.set_named_property("__nsEsmForget", forget)?;

let report = env.create_function_from_closure("__nsEsmReportError", |ctx: CallContext| {

let report = arg_string(&ctx, 0)?.unwrap_or_default();

crate::debug_output(&format!("[NativeScript] Uncaught error evaluating module: {report}\n"));

crate::store_last_js_error(report);

ctx.env.get_undefined()

})?;

global.set_named_property("__nsEsmReportError", report)?;

let configure = env.create_function_from_closure("__nsModuleConfigureLoader", |ctx: CallContext| {

let json = arg_string(&ctx, 0)?.unwrap_or_default();

esm_loader::configure_loader(&json).map_err(napi::Error::from_reason)?;

ctx.env.get_undefined()

})?;

global.set_named_property("__nsModuleConfigureLoader", configure)?;

let boot_complete = env.create_function_from_closure("__nsModuleSetDevBootComplete", |ctx: CallContext| {

esm_loader::set_dev_boot_complete(ctx.get::<JsUnknown>(0)?.coerce_to_bool()?.get_value()?);

ctx.env.get_undefined()

})?;

global.set_named_property("__nsModuleSetDevBootComplete", boot_complete)?;

eval(env, RUNNER, "<module-runner>").map_err(|()| {

napi::Error::from_reason(format!("module runner failed to install: {}", take_exception(env)))

})?;

Ok(())

}

/// Run the entry module the host passes to `runtime_runscript` (`filename`, absolute or relative

/// to the app root). Failures are reported through `__nsEsmReportError` when the graph settles.

pub fn run_entry(env: &Env, filename: &str, app_root: &str) -> napi::Result<()> {

let key = esm_loader::entry_key(filename, app_root);

let global = env.get_global()?;

let runner: JsObject = global.get_named_property("__nsEsmRunner")?;

let run_entry: napi::JsFunction = runner.get_named_property("runEntry")?;

run_entry.call(Some(&runner), &[env.create_string(&key)?])?;

Ok(())

}

/// The module runner. Engine-conservative like the prelude (function expressions, no syntax the

/// transform would have to lower), since it's evaluated as a classic script on every engine.

pub const RUNNER: &str = r#"

(function (g) {

'use strict';

if (typeof g.__nsEsmLoad !== 'function' || g.__nsEsmRunner) { return; }

var load = g.__nsEsmLoad;

var resolve = g.__nsEsmResolve;

var prefetch = g.__nsEsmPrefetch;

var isVolatile = g.__nsEsmIsVolatile;

var registryKey = g.__nsEsmRegistryKey;

var forget = g.__nsEsmForget;

var report = g.__nsEsmReportError;

// Registry key -> { key, exports, promise, evaluated, stack }. `stack` is the static import

// chain the module was first reached through, which is how a cycle is recognized.

var registry = new Map();

function newNamespace() {

var ns = Object.create(null);

Object.defineProperty(ns, Symbol.toStringTag, { value: 'Module' });

return ns;

}

// `import.meta`: `url` (a file:/// URL, as bundlers' `new URL(x, import.meta.url)` expect),

// `filename` and `dirname`. A served module's identity is its URL alone.

function importMeta(key) {

if (/^https?:\/\//.test(key) || key === 'ns:module') { return { url: key }; }

var path = key.indexOf('\\\\?\\') === 0 ? key.slice(4) : key;

var sep = Math.max(path.lastIndexOf('\\'), path.lastIndexOf('/'));

return {

url: 'file:///' + path.replace(/\\/g, '/'),

filename: path,

dirname: sep < 0 ? '' : path.slice(0, sep)

};

}

function defineExport(exports, name, getter) {

Object.defineProperty(exports, name, { enumerable: true, configurable: true, get: getter });

}

// `export * from`: every name but `default` and the ones the module declares itself.

function exportAll(exports, source) {

for (var name in source) {

if (name !== 'default' && name !== '__esModule' && !(name in exports)) {

defineExport(exports, name, (function (n) { return function () { return source[n]; }; })(name));

}

function describe(e) {

var text = String(e);

var stack = e && e.stack ? String(e.stack) : '';

if (!stack) { return text; }

return stack.indexOf(text) >= 0 ? stack : text + '\n' + stack;

}

function evict(key) {

var removed = registry.delete(key);

forget([key]);

return removed;

}

// Load and start evaluating `key`. A load failure throws and leaves nothing registered, so a

// later import retries it.

function instantiate(key, spec, referrer, parentStack) {

var loaded = load(key, spec, referrer);

var record = { key: key, exports: newNamespace(), promise: null, evaluated: false, stack: parentStack.concat([key]) };

registry.set(key, record);

// Fetch the dependencies served over HTTP concurrently before the body awaits them in turn.

var deps = [];

for (var i = 0; i < loaded.deps.length; i++) {

var dep = resolve(loaded.deps[i], key);

if (!registry.has(dep) && deps.indexOf(dep) < 0) { deps.push(dep); }

}

if (deps.length > 1) { prefetch(deps); }

var exports = record.exports;

record.promise = loaded.fn.call(

undefined,

exports,

importMeta(key),

function (s) { return importFrom(s, record); },

function (s) { return dynamicImport(s, key); },

function (source) { exportAll(exports, source); },

function (name, getter) { defineExport(exports, name, getter); }

).then(function () {

record.evaluated = true;

return exports;

});

return record;

}

// Static import from `importer`'s body.

function importFrom(spec, importer) {

var key = resolve(spec, importer.key);

var record = registry.get(key);

if (record) {

// Inside an import cycle, take the partially evaluated exports: their getters fill in once

// the module's body runs.

if (record.evaluated || importer.stack.indexOf(key) >= 0) { return record.exports; }

return record.promise;

}

try {

return instantiate(key, spec, importer.key, importer.stack).promise;

} catch (e) {

return Promise.reject(e);

}

// `import()`: settles with the namespace once the graph (including any top-level await) has

// evaluated, or rejects with the real error.

function dynamicImport(spec, referrer) {

try {

var key = resolve(spec, referrer);

// Volatile URLs (configureLoader) are re-fetched on every import.

if (isVolatile(key)) { evict(key); }

var record = registry.get(key) || instantiate(key, spec, referrer, []);

return record.promise;

} catch (e) {

return Promise.reject(e);

}

function runEntry(key) {

var promise;

try {

promise = (registry.get(key) || instantiate(key, key, null, [])).promise;

} catch (e) {

promise = Promise.reject(e);

}

return promise.then(null, function (e) { report(describe(e)); });

}

// `ns:module`'s `invalidateModules(urls)`: registry eviction plus a one-shot cache-bust nonce on

// each evicted URL's next fetch. Importers already linked keep the old exports; the HMR client

// re-imports the graph above them.

g.__nsModuleInvalidate = function (urls) {

if (!Array.isArray(urls)) { throw new TypeError('invalidateModules expects an array of URL strings'); }

var keys = [];

for (var i = 0; i < urls.length; i++) {

if (typeof urls[i] !== 'string') { throw new TypeError('invalidateModules: urls[' + i + '] must be a string'); }

var key = registryKey(urls[i]);

if (key && keys.indexOf(key) < 0) { keys.push(key); }

}

var removed = 0;

for (var j = 0; j < keys.length; j++) {

if (registry.delete(keys[j])) { removed++; }

}

forget(keys);

return removed;

};

// `ns:module`'s `getLoadedModuleUrls()`: the URL-keyed (served) modules currently registered.

g.__nsModuleLoadedUrls = function () {

var urls = [];

registry.forEach(function (record, key) {

if (key.indexOf('://') >= 0) { urls.push(key); }

});

return urls.sort();

};

Object.defineProperty(g, '__nsEsmRunner', {

value: Object.freeze({ runEntry: runEntry, importModule: dynamicImport }),

configurable: true

});

})(globalThis);

'module-runner-ok'

"#;

#[cfg(test)]

mod tests {

use super::transform;

#[test]

fn exports_are_getters_hoisted_above_awaited_imports() {

let out = transform(

"import d, { a } from './dep.mjs';\nexport let n = a;\nexport default d;\nexport * from './star.mjs';",

"C:/app/main.mjs",

)

.unwrap();

assert_eq!(out.deps, vec!["./dep.mjs".to_string(), "./star.mjs".to_string()]);

assert!(out.code.starts_with("(async function (__vite_ssr_exports__"), "{}", out.code);

let getter = out.code.find("Object.defineProperty(__vite_ssr_exports__, \"n\"").unwrap();

let import = out.code.find("await __vite_ssr_import__(\"./dep.mjs\"").unwrap();

assert!(getter < import, "{}", out.code);

assert!(out.code.contains("__vite_ssr_exportAll__("), "{}", out.code);

}

#[test]

fn import_meta_and_dynamic_import_go_through_the_runner() {

let out = transform("const u = import.meta.url; const m = () => import('./lazy.mjs');", "k").unwrap();

assert!(out.code.contains("__vite_ssr_import_meta__.url"), "{}", out.code);

assert!(out.code.contains("__vite_ssr_dynamic_import__(\"./lazy.mjs\")"), "{}", out.code);

assert!(out.deps.is_empty());

}

#[test]

fn syntax_errors_name_the_module_and_location() {

let err = transform("export const ok = 1;\nexport const = 2;", "C:/app/bad.mjs").err().unwrap();

assert!(err.contains("(C:/app/bad.mjs:2:"), "{err}");

}

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