Attask

An approach to conditional promise chains with state and providers.

const Attask = require("attask");
 
Attask
  .sync()
  .store({secret: 10});
  .provide([0, 1, 2])
  .must(
      collection => collection.push(4),
      (collection, store) => collection.push(store.get("secret"))
  )
  .finally(console.log)
  .run()

The above example will output [0, 1, 2, 4, 10]

Getting Started

npm install --save attask 

Attask can be instantiated in a couple of ways but the simplest way to create a new chain with the static methods async or sync

Attask.async() tells attask to execute the task chains in parallel -

Attask
  .async()
  .must(
      () => new Promise((resolve, reject) => setTimeout(() => {
        console.log("A");
        resolve(); // Simulate background task with timeout
      }, 2500))
      () => console.log("B"),
      () => console.log("C")
  )
  .finally(() => console.log("DONE"));
.run();

Output

• 0ms: B
• 0ms: C
• 2.5ms: A
• 2.5ms: DONE

Attask.sync() in contrast, will guarantee execute the tasks sequentially -

Attask
  .sync()
  .must(
      () => new Promise((resolve, reject) => setTimeout(() => {
        console.log("A");
        resolve(); // Simulate background task with timeout
      }, 2500))
      () => console.log("B"),
      () => console.log("C")
  )
  .finally(() => console.log("DONE"));
.run();

Output

• 2.5ms: A
• 2.5ms: B
• 2.5ms: C
• 2.5ms: DONE

Must, Might or Wont

In order to populate chains with actions you use the methods must, might, or wont.

• Tasks added with must will abort all other tasks and pending tasks on failure
• Tasks added with wont must fail and will abort all other tasks and pending tasks on success
• Tasks added with might will not cancel other tasks when failed

Tasks in must and might and wont groupings will execute in parallel even with the sync flag.

Attask
  .must(
    () => console.log("A"),
    () => console.log("B")
  )
  .might(
    () => console.log("C")
  )
  .wont(
    () => throw Error("Intentional Error")
  )
.run()

Tasks

Tasks provided can be one of two things.

A function that accepts the provider and store. Can return a promise for async execution.

function task(provider, store) {
  //...
}
 
//...
.must(
  task,
  task,
  task
)

A class that implements the run method that accepts the provider and store. This can also return a promise

class Task {
  
  function run(provider, store) {
    //...
  }
 
}
 
//...
.must(
  Task
  Task
  Task
)

Provider

Attask chains can be provided an attachment for the current work load. This attachment will be used as the first argument for a task callback.

const attask = Attask.provide([]); // An empty array is the provider
 
attask.must(collection => collection.push(0));
 
attask.finally(console.log);
 
attask.run(); //Will log "[0]"

State

Attask chains can be passed a state that is then abstracted in to a store object. This store object will be used as the second argument for a task callback

Attask
  .provide(app)
  .store({ logger: "debug" })
  .must(
    (app, store) => app.use(logger(store.get("logger"))),
    app => app.use(cors())
  )
.run();

Here's a list of the methods available on the store -

    resolve<T>(key:string):T;
    has(key:string):boolean;
    set(key:string, entry:any):AttaskStore;
    remove(key:string):AttaskStore;
    keys():string[];
    collect<T>(...key: string[]): T[];
    hasAny(...keys: string[]): boolean;
    hasNone(...keys: string[]): boolean;
    hasAll(...keys: string[]): boolean;
    has(key: string): boolean;
    resolve<T>(key: string): T;
    get<T>(key: string, ifNotFound?: T): {};
    any<T>(...keys: any[]): AttaskOptional<T>;
    all<T>(...keys: any[]): AttaskOptional<T>[];
    absorb(source: AttaskStore | any): void;

Note, you can also store an object that implements the first 5 methods above. Attask will see the object's signature and expand the task store with that object's elements.

Optionals

AttaskOptional objects returned from any or all have the following methods

is(...resolution):boolean
exists():boolean
get(ifNotFound:T = null):T

Chaining

To append another attask chain use the after method

Attask
  .must(() => console.log("A"))
  .after()
  .must(() => console.log("B")) //A brand new attask chain
.run()

By default a child chain will not use the provider available in the parent or the store available in the parent, when changed.

In order to keep this connection alive you can use the link directive to let attask know that the child chain relies on the parent provider even when changed.

const parent = Attask.must(() => console.log("A"));
const child = parent.after().must(() => console.log("B"));
 
child.link(); //Will inherit any configuration changes
 
parent.provide([]); //child will now have this provider because it was linked
 

Errors

Use catch to use your own error handler, by default attask's error handler is a console.error call.

Attask
  .must(() => throw new Error("Oops"))
  .catch(error => console.error("ERROR", error)
.run();

Silence

In order to disable error handling without a noop function for catch, you can simply use the silence directive

Attask
  .must(() => throw new Error("Oops"))
  .silence()
.run();

All methods available on Attask (@see attask.d.ts)

    sync(): Attask<P>;
    static sync<P>(): Attask<P>;
    async(): Attask<P>;
    static async<P>(): Attask<P>;
    store(source: AttaskStore | any): Attask<P>;
    static store<P>(source: AttaskStore | any): Attask<P>;
    absorb(source: AttaskStore | any): Attask<P>;
    provide(provider: P): Attask<P>;
    static provide<P>(provider: P): Attask<P>;
    must(...task: TaskerTask<P>[]): Attask<P>;
    static must<P>(...task: TaskerTask<P>[]): Attask<P>;
    wont(...task: TaskerTask<P>[]): Attask<P>;
    static wont<P>(...task: TaskerTask<P>[]): Attask<P>;
    might(...task: TaskerTask<P>[]): Attask<P>;
    static might<P>(...task: TaskerTask<P>[]): Attask<P>;
    catch(handler: AttaskListener<P, any> | any): Attask<P>;
    static catch<P>(handler: AttaskListener<P, any> | any): Attask<P>;
    silence(): Attask<P>;
    static silence<P>(): Attask<P>;
    unsilence(): Attask<P>;
    static unsilence<P>(): Attask<P>;
    link(): Attask<P>;
    static link<P>(): Attask<P>;
    unlink(): Attask<P>;
    static unlink<P>(): Attask<P>;
    finally(batchCompletion: AttaskListener<P, AttaskResult<P>> | any): Attask<P>;
    after(): Attask<P>;
    run(provider?: P, config?: AttaskState): any;

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