Inflight Functions

The concepts of preflight and inflight in winglang are described here. In TypeScript, this is analogous to the difference between the main function (preflight) and the inflight function.

Functions and inflight

Some resources, like cloud.Function, run code in the cloud. This code is called an inflight closure.

To create an inflight closure in TypeScript, you can use the inflight() function and pass it an async closure:

import { main, cloud, inflight } from "@wingcloud/framework";

main((root) => {
  new cloud.Function(
    root,
    "MyFn",
    inflight(async () => {
      // This code runs in the deployed cloud function
      return "Wing!";
    })
  );
});

Lifting objects into inflight closures

Inflight closures do not run in the same environment as the rest of the code, so you can't just reference variables from the outside. The lift() function ensures you have an interface with the data you need. This includes the inflight APIs for the lifted resources:

import { main, cloud, lift } from "@wingcloud/framework";

main((root) => {
  const bucket = new cloud.Bucket(root, "MyBucket");
  const plainData = "Wing!";

  new cloud.Function(
    root,
    "MyFn",
    lift({ bucket, plainData }).inflight(async ({ bucket, plainData }) => {
      // note that inflight methods are always asynchronous
      await bucket.put("hello.txt", plainData);
      return plainData;
    })
  );
});

Inflight closures themselves can also be lifted. Once lifted, they can be called like normal closure:

import { main, lift } from "@wingcloud/framework";

main((root) => {
  const myInflight = inflight(async () => {
    return "Wing!";
  });

  lift({ myInflight }).inflight(async ({ myInflight }) => {
    return myInflight();
  });
});

Normal functions and classes cannot be lifted. Unlike other variables, imports can be referenced as-is from within inflight closures. The imports will be bundled into the inflight's environment.

import { main, inflight } from "@wingcloud/framework";
import assert from "node:assert";

main((root) => {
  inflight(async () => {
    assert.equal(1, 1);
  });
});

Permissions

When lift() is used with resources, permissions are granted automatically to access them in the cloud. By default, these permissions are permissive and allow all actions on the resource. To restrict the permissions, chain grant() calls to your lift():

import { main, cloud, lift } from "@wingcloud/framework";

main((root) => {
  const bucket = new cloud.Bucket(root, "MyBucket");

  new cloud.Function(
    root,
    "MyFn",
    lift({ bucket })
      .grant({ bucket: ["get"] })
      .inflight(async ({ bucket }) => {
        await bucket.put("hello.txt", "Wing!");
        //           ^^^ Type error, no `put` permissions!
        return "Wing!";
      })
  );
});

Testing

wing test runs all tests within your main. To define a test, use the test() function provided as the second argument to main:

import { main, cloud, inflight, lift } from "@wingcloud/framework";
import assert from "node:assert";

main((root, test) => {
  const fn = new cloud.Function(
    root,
    "MyFn",
    inflight(async () => {
      return "Wing!";
    })
  );

  test(
    // name of the test
    "MyFn returns 'Wing!'",
    // inflight function to run as the test
    lift({ fn }).inflight(async ({ fn }) => {
      assert.equal(await fn.invoke(), "Wing!");
    })
  );
});