/
edge-runtime.ts
202 lines (180 loc) · 5.98 KB
/
edge-runtime.ts
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import type { DispatchFetch, ErrorHandler, RejectionHandler } from './types'
import type { EdgeVMOptions, EdgeContext } from '@edge-runtime/vm'
import { EdgeVM } from '@edge-runtime/vm'
interface Options<T extends EdgeContext> extends EdgeVMOptions<T> {
/**
* Code to be evaluated as the VM for the Runtime is created. This is handy
* to run code directly instead of first creating the runtime and then
* evaluating.
*/
initialCode?: string
}
/**
* Store handlers that the user defined from code so that we can invoke them
* from the Node.js realm.
*/
let unhandledRejectionHandlers: RejectionHandler[]
let uncaughtExceptionHandlers: ErrorHandler[]
/**
* An EdgeVM that also allows to add and remove event listeners for unhandled
* rejections and FetchEvent. It also allows to dispatch fetch events which
* enables it to work behind a server.
*/
export class EdgeRuntime<
T extends EdgeContext = EdgeContext
> extends EdgeVM<T> {
public readonly dispatchFetch: DispatchFetch
constructor(options?: Options<T>) {
super({
...options,
extend: (context) => {
return options?.extend?.(context) ?? (context as EdgeContext & T)
},
})
defineHandlerProps({
object: this,
setterName: '__onUnhandledRejectionHandler',
setter: (handlers: RejectionHandler[]) =>
(unhandledRejectionHandlers = handlers),
getterName: '__rejectionHandlers',
getter: () => unhandledRejectionHandlers,
})
defineHandlerProps({
object: this,
setterName: '__onErrorHandler',
setter: (handlers: ErrorHandler[]) =>
(uncaughtExceptionHandlers = handlers),
getterName: '__errorHandlers',
getter: () => uncaughtExceptionHandlers,
})
this.evaluate<void>(getDefineEventListenersCode())
this.dispatchFetch = this.evaluate<DispatchFetch>(getDispatchFetchCode())
if (options?.initialCode) {
this.evaluate(options.initialCode)
}
}
}
/**
* Define system-level handlers to make sure that we report to the user
* whenever there is an unhandled rejection or exception before the process crashes.
*/
process.on(
'unhandledRejection',
function invokeRejectionHandlers(reason, promise) {
unhandledRejectionHandlers?.forEach((handler) =>
handler({ reason, promise })
)
}
)
process.on('uncaughtException', function invokeErrorHandlers(error) {
uncaughtExceptionHandlers?.forEach((handler) => handler(error))
})
/**
* Generates polyfills for addEventListener and removeEventListener. It keeps
* all listeners in hidden property __listeners. It will also call a hook
* `__onUnhandledRejectionHandler` and `__onErrorHandler` when unhandled rejection
* events are added or removed and prevent from having more than one FetchEvent
* handler.
*/
function getDefineEventListenersCode() {
return `
Object.defineProperty(self, '__listeners', {
configurable: false,
enumerable: false,
value: {},
writable: true,
})
function __conditionallyUpdatesHandlerList(eventType) {
if (eventType === 'unhandledrejection') {
self.__onUnhandledRejectionHandler = self.__listeners[eventType];
} else if (eventType === 'error') {
self.__onErrorHandler = self.__listeners[eventType];
}
}
function addEventListener(type, handler) {
const eventType = type.toLowerCase();
if (eventType === 'fetch' && self.__listeners.fetch) {
throw new TypeError('You can register just one "fetch" event listener');
}
self.__listeners[eventType] = self.__listeners[eventType] || [];
self.__listeners[eventType].push(handler);
__conditionallyUpdatesHandlerList(eventType);
}
function removeEventListener(type, handler) {
const eventType = type.toLowerCase();
if (self.__listeners[eventType]) {
self.__listeners[eventType] = self.__listeners[eventType].filter(item => {
return item !== handler;
});
if (self.__listeners[eventType].length === 0) {
delete self.__listeners[eventType];
}
}
__conditionallyUpdatesHandlerList(eventType);
}
`
}
/**
* Generates the code to dispatch a FetchEvent invoking the handlers defined
* for such events. In case there is no event handler defined it will throw
* an error.
*/
function getDispatchFetchCode() {
return `(async function dispatchFetch(input, init) {
const request = new Request(input, init);
const event = new FetchEvent(request);
if (!self.__listeners.fetch) {
throw new Error("No fetch event listeners found");
}
const getResponse = ({ response, error }) => {
if (error || !response || !(response instanceof Response)) {
console.error(error ? error.toString() : 'The event listener did not respond')
response = new Response(null, {
statusText: 'Internal Server Error',
status: 500
})
}
response.waitUntil = () => Promise.all(event.awaiting);
response.headers.delete('content-encoding');
response.headers.delete('transform-encoding');
response.headers.delete('content-length');
return response;
}
try {
await self.__listeners.fetch[0].call(event, event)
} catch (error) {
return getResponse({ error })
}
return Promise.resolve(event.response)
.then(response => getResponse({ response }))
.catch(error => getResponse({ error }))
})`
}
/**
* Defines a readable property on the VM and the corresponding writable property
* on the VM's context. These properties are not enumerable nor updatable.
*/
function defineHandlerProps({
object: instance,
setterName,
setter: setter,
getterName,
getter,
}: {
object: EdgeRuntime
setterName: string
setter: (_: any) => void
getterName: string
getter: () => any
}) {
Object.defineProperty(instance.context, setterName, {
set: setter,
configurable: false,
enumerable: false,
})
Object.defineProperty(instance, getterName, {
get: getter,
configurable: false,
enumerable: false,
})
}