442 lines
20 KiB
TypeScript
442 lines
20 KiB
TypeScript
/**
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* Zone is a mechanism for intercepting and keeping track of asynchronous work.
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*
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* A Zone is a global object which is configured with rules about how to intercept and keep track
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* of the asynchronous callbacks. Zone has these responsibilities:
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*
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* 1. Intercept asynchronous task scheduling
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* 2. Wrap callbacks for error-handling and zone tracking across async operations.
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* 3. Provide a way to attach data to zones
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* 4. Provide a context specific last frame error handling
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* 5. (Intercept blocking methods)
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*
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* A zone by itself does not do anything, instead it relies on some other code to route existing
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* platform API through it. (The zone library ships with code which monkey patches all of the
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* browsers's asynchronous API and redirects them through the zone for interception.)
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*
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* In its simplest form a zone allows one to intercept the scheduling and calling of asynchronous
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* operations, and execute additional code before as well as after the asynchronous task. The rules
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* of interception are configured using [ZoneConfig]. There can be many different zone instances in
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* a system, but only one zone is active at any given time which can be retrieved using
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* [Zone#current].
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*
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*
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*
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* ## Callback Wrapping
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*
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* An important aspect of the zones is that they should persist across asynchronous operations. To
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* achieve this, when a future work is scheduled through async API, it is necessary to capture, and
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* subsequently restore the current zone. For example if a code is running in zone `b` and it
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* invokes `setTimeout` to scheduleTask work later, the `setTimeout` method needs to 1) capture the
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* current zone and 2) wrap the `wrapCallback` in code which will restore the current zone `b` once
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* the wrapCallback executes. In this way the rules which govern the current code are preserved in
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* all future asynchronous tasks. There could be a different zone `c` which has different rules and
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* is associated with different asynchronous tasks. As these tasks are processed, each asynchronous
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* wrapCallback correctly restores the correct zone, as well as preserves the zone for future
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* asynchronous callbacks.
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*
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* Example: Suppose a browser page consist of application code as well as third-party
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* advertisement code. (These two code bases are independent, developed by different mutually
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* unaware developers.) The application code may be interested in doing global error handling and
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* so it configures the `app` zone to send all of the errors to the server for analysis, and then
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* executes the application in the `app` zone. The advertising code is interested in the same
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* error processing but it needs to send the errors to a different third-party. So it creates the
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* `ads` zone with a different error handler. Now both advertising as well as application code
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* create many asynchronous operations, but the [Zone] will ensure that all of the asynchronous
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* operations created from the application code will execute in `app` zone with its error
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* handler and all of the advertisement code will execute in the `ads` zone with its error handler.
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* This will not only work for the async operations created directly, but also for all subsequent
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* asynchronous operations.
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*
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* If you think of chain of asynchronous operations as a thread of execution (bit of a stretch)
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* then [Zone#current] will act as a thread local variable.
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*
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*
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*
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* ## Asynchronous operation scheduling
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*
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* In addition to wrapping the callbacks to restore the zone, all operations which cause a
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* scheduling of work for later are routed through the current zone which is allowed to intercept
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* them by adding work before or after the wrapCallback as well as using different means of
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* achieving the request. (Useful for unit testing, or tracking of requests). In some instances
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* such as `setTimeout` the wrapping of the wrapCallback and scheduling is done in the same
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* wrapCallback, but there are other examples such as `Promises` where the `then` wrapCallback is
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* wrapped, but the execution of `then` in triggered by `Promise` scheduling `resolve` work.
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*
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* Fundamentally there are three kinds of tasks which can be scheduled:
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*
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* 1. [MicroTask] used for doing work right after the current task. This is non-cancelable which is
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* guaranteed to run exactly once and immediately.
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* 2. [MacroTask] used for doing work later. Such as `setTimeout`. This is typically cancelable
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* which is guaranteed to execute at least once after some well understood delay.
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* 3. [EventTask] used for listening on some future event. This may execute zero or more times, with
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* an unknown delay.
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*
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* Each asynchronous API is modeled and routed through one of these APIs.
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*
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*
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* ### [MicroTask]
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*
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* [MicroTask]s represent work which will be done in current VM turn as soon as possible, before VM
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* yielding.
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*
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*
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* ### [TimerTask]
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*
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* [TimerTask]s represents work which will be done after some delay. (Sometimes the delay is
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* approximate such as on next available animation frame). Typically these methods include:
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* `setTimeout`, `setImmediate`, `setInterval`, `requestAnimationFrame`, and all browser specif
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* variants.
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*
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*
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* ### [EventTask]
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*
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* [EventTask]s represents a request to create a listener on an event. Unlike the other task
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* events may never be executed, but typically execute more then once. There is no queue of
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* events, rather their callbacks are unpredictable both in order and time.
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*
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*
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* ## Global Error Handling
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*
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*
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* ## Composability
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*
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* Zones can be composed together through [Zone.fork()]. A child zone may create its own set of
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* rules. A child zone is expected to either:
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*
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* 1. Delegate the interception to a parent zone, and optionally add before and after wrapCallback
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* hook.s
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* 2) Or process the request itself without delegation.
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*
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* Composability allows zones to keep their concerns clean. For example a top most zone may chose
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* to handle error handling, while child zones may chose to do user action tracking.
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*
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*
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* ## Root Zone
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*
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* At the start the browser will run in a special root zone, which is configure to behave exactly
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* like the platform, making any existing code which is not-zone aware behave as expected. All
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* zones are children of the root zone.
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*
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*/
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interface Zone {
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/**
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*
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* @returns {Zone} The parent Zone.
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*/
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parent: Zone;
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/**
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* @returns {string} The Zone name (useful for debugging)
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*/
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name: string;
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/**
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* Returns a value associated with the `key`.
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*
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* If the current zone does not have a key, the request is delegated to the parent zone. Use
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* [ZoneSpec.properties] to configure the set of properties asseciated with the current zone.
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*
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* @param key The key to retrieve.
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* @returns {any} Tha value for the key, or `undefined` if not found.
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*/
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get(key: string): any;
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/**
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* Used to create a child zone.
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*
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* @param zoneSpec A set of rules which the child zone should follow.
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* @returns {Zone} A new child zone.
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*/
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fork(zoneSpec: ZoneSpec): Zone;
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/**
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* Wraps a callback function in a new function which will properly restore the current zone upon
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* invocation.
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*
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* The wrapped function will properly forward `this` as well as `arguments` to the `callback`.
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*
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* Before the function is wrapped the zone can intercept the `callback` by declaring
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* [ZoneSpec.onIntercept].
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*
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* @param callback the function which will be wrapped in the zone.
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* @param source A unique debug location of the API being wrapped.
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* @returns {function(): *} A function which will invoke the `callback` through [Zone.runGuarded].
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*/
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wrap(callback: Function, source: string): Function;
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/**
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* Invokes a function in a given zone.
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*
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* The invocation of `callback` can be intercepted be declaring [ZoneSpec.onInvoke].
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*
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* @param callback The function to invoke.
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* @param applyThis
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* @param applyArgs
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* @param source A unique debug location of the API being invoked.
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* @returns {any} Value from the `callback` function.
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*/
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run<T>(callback: Function, applyThis?: any, applyArgs?: any[], source?: string): T;
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/**
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* Invokes a function in a given zone and catches any exceptions.
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*
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* Any exceptions thrown will be forwarded to [Zone.HandleError].
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*
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* The invocation of `callback` can be intercepted be declaring [ZoneSpec.onInvoke]. The
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* handling of exceptions can intercepted by declaring [ZoneSpec.handleError].
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*
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* @param callback The function to invoke.
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* @param applyThis
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* @param applyArgs
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* @param source A unique debug location of the API being invoked.
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* @returns {any} Value from the `callback` function.
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*/
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runGuarded<T>(callback: Function, applyThis?: any, applyArgs?: any[], source?: string): T;
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/**
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* Execute the Task by restoring the [Zone.currentTask] in the Task's zone.
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*
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* @param callback
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* @param applyThis
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* @param applyArgs
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* @returns {*}
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*/
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runTask(task: Task, applyThis?: any, applyArgs?: any): any;
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scheduleMicroTask(source: string, callback: Function, data?: TaskData, customSchedule?: (task: Task) => void): MicroTask;
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scheduleMacroTask(source: string, callback: Function, data: TaskData, customSchedule: (task: Task) => void, customCancel: (task: Task) => void): MacroTask;
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scheduleEventTask(source: string, callback: Function, data: TaskData, customSchedule: (task: Task) => void, customCancel: (task: Task) => void): EventTask;
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/**
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* Allows the zone to intercept canceling of scheduled Task.
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*
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* The interception is configured using [ZoneSpec.onCancelTask]. The default canceler invokes
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* the [Task.cancelFn].
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*
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* @param task
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* @returns {any}
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*/
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cancelTask(task: Task): any;
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}
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interface ZoneType {
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/**
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* @returns {Zone} Returns the current [Zone]. Returns the current zone. The only way to change
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* the current zone is by invoking a run() method, which will update the current zone for the
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* duration of the run method callback.
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*/
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current: Zone;
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/**
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* @returns {Task} The task associated with the current execution.
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*/
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currentTask: Task;
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}
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/**
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* Provides a way to configure the interception of zone events.
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*
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* Only the `name` property is required (all other are optional).
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*/
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interface ZoneSpec {
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/**
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* The name of the zone. Usefull when debugging Zones.
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*/
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name: string;
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/**
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* A set of properties to be associated with Zone. Use [Zone.get] to retrive them.
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*/
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properties?: {
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[key: string]: any;
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};
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/**
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* Allows the interception of zone forking.
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*
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* When the zone is being forked, the request is forwarded to this method for interception.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param zoneSpec The argument passed into the `fork` method.
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*/
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onFork?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, zoneSpec: ZoneSpec) => Zone;
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/**
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* Allows interception of the wrapping of the callback.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param delegate The argument passed into the `warp` method.
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* @param source The argument passed into the `warp` method.
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*/
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onIntercept?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, delegate: Function, source: string) => Function;
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/**
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* Allows interception of the callback invocation.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param delegate The argument passed into the `run` method.
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* @param applyThis The argument passed into the `run` method.
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* @param applyArgs The argument passed into the `run` method.
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* @param source The argument passed into the `run` method.
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*/
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onInvoke?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, delegate: Function, applyThis: any, applyArgs: any[], source: string) => any;
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/**
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* Allows interception of the error handling.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param error The argument passed into the `handleError` method.
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*/
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onHandleError?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, error: any) => boolean;
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/**
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* Allows interception of task scheduling.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param task The argument passed into the `scheduleTask` method.
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*/
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onScheduleTask?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, task: Task) => Task;
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onInvokeTask?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, task: Task, applyThis: any, applyArgs: any) => any;
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/**
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* Allows interception of task cancalation.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param task The argument passed into the `cancelTask` method.
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*/
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onCancelTask?: (parentZoneDelegate: ZoneDelegate, currentZone: Zone, targetZone: Zone, task: Task) => any;
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/**
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* Notifies of changes to the task queue empty status.
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*
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* @param parentZoneDelegate Dalegate which performs the parent [ZoneSpec] operation.
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* @param currentZone The current [Zone] where the current interceptor has beed declared.
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* @param targetZone The [Zone] which originally received the request.
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* @param isEmpty
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*/
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onHasTask?: (delegate: ZoneDelegate, current: Zone, target: Zone, hasTaskState: HasTaskState) => void;
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}
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/**
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* A delegate when intercepting zone operations.
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*
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* A ZoneDelegate is needed because a child zone can't simply invoke a method on a parent zone. For
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* example a child zone wrap can't just call parent zone wrap. Doing so would create a callback
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* which is bound to the parent zone. What we are interested is intercepting the callback before it
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* is bound to any zone. Furthermore, we also need to pass the targetZone (zone which received the
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* original request) to the delegate.
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*
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* The ZoneDelegate methods mirror those of Zone with an addition of extra targetZone argument in
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* the method signature. (The original Zone which received the request.) Some methods are renamed
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* to prevent confusion, because they have slightly different semantics and arguments.
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*
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* - `wrap` => `intercept`: The `wrap` method delegates to `intercept`. The `wrap` method returns
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* a callback which will run in a given zone, where as intercept allows wrapping the callback
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* so that additional code can be run before and after, but does not associated the callback
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* with the zone.
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* - `run` => `invoke`: The `run` method delegates to `invoke` to perform the actual execution of
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* the callback. The `run` method switches to new zone; saves and restores the `Zone.current`;
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* and optionally performs error handling. The invoke is not responsible for error handling,
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* or zone management.
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*
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* Not every method is usually overwritten in the child zone, for this reason the ZoneDelegate
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* stores the closest zone which overwrites this behavior along with the closest ZoneSpec.
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*
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* NOTE: We have tried to make this API analogous to Event bubbling with target and current
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* properties.
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*
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* Note: The ZoneDelegate treats ZoneSpec as class. This allows the ZoneSpec to use its `this` to
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* store internal state.
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*/
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interface ZoneDelegate {
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zone: Zone;
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fork(targetZone: Zone, zoneSpec: ZoneSpec): Zone;
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intercept(targetZone: Zone, callback: Function, source: string): Function;
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invoke(targetZone: Zone, callback: Function, applyThis: any, applyArgs: any[], source: string): any;
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handleError(targetZone: Zone, error: any): boolean;
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scheduleTask(targetZone: Zone, task: Task): Task;
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invokeTask(targetZone: Zone, task: Task, applyThis: any, applyArgs: any): any;
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cancelTask(targetZone: Zone, task: Task): any;
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hasTask(targetZone: Zone, isEmpty: HasTaskState): void;
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}
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declare type HasTaskState = {
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microTask: boolean;
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macroTask: boolean;
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eventTask: boolean;
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change: TaskType;
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};
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/**
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* Task type: `microTask`, `macroTask`, `eventTask`.
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*/
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declare type TaskType = string;
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/**
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*/
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interface TaskData {
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/**
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* A periodic [MacroTask] is such which get automatically rescheduled after it is executed.
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*/
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isPeriodic?: boolean;
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/**
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* Delay in milliseconds when the Task will run.
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*/
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delay?: number;
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}
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/**
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* Represents work which is executed with a clean stack.
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*
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* Tasks are used in Zones to mark work which is performed on clean stack frame. There are three
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* kinds of task. [MicroTask], [MacroTask], and [EventTask].
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*
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* A JS VM can be modeled as a [MicroTask] queue, [MacroTask] queue, and [EventTask] set.
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*
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* - [MicroTask] queue represents a set of tasks which are executing right after the current stack
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* frame becomes clean and before a VM yield. All [MicroTask]s execute in order of insertion
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* before VM yield and the next [MacroTask] is executed.
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* - [MacroTask] queue represents a set of tasks which are executed one at a time after each VM
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* yield. The queue is order by time, and insertions can happen in any location.
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* - [EventTask] is a set of tasks which can at any time be inserted to the head of the [MacroTask]
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* queue. This happens when the event fires.
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*
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*/
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interface Task {
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/**
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* Task type: `microTask`, `macroTask`, `eventTask`.
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*/
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type: TaskType;
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/**
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* Debug string representing the API which requested the scheduling of the task.
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*/
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source: string;
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/**
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* The Function to be used by the VM on entering the [Task]. This function will delegate to
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* [Zone.runTask] and delegate to `callback`.
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*/
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invoke: Function;
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/**
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* Function which needs to be executed by the Task after the [Zone.currentTask] has been set to
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* the current task.
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*/
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callback: Function;
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/**
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* Task specific options associated with the current task. This is passed to the `scheduleFn`.
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*/
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data: TaskData;
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/**
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* Represents the default work which needs to be done to schedule the Task by the VM.
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*
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* A zone may chose to intercept this function and perform its own scheduling.
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*/
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scheduleFn: (task: Task) => void;
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/**
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* Represents the default work which needs to be done to un-schedule the Task from the VM. Not all
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* Tasks are cancelable, and therefore this method is optional.
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*
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* A zone may chose to intercept this function and perform its own scheduling.
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*/
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cancelFn: (task: Task) => void;
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/**
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* @type {Zone} The zone which will be used to invoke the `callback`. The Zone is captured
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* at the time of Task creation.
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*/
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zone: Zone;
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}
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interface MicroTask extends Task {
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}
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interface MacroTask extends Task {
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}
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interface EventTask extends Task {
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}
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declare var Zone: ZoneType;
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