Description of problem

Given the following preProcess and postProcess examples within a respec config:

var respecConfig = {
  // ...
  preProcess: [
    async () => {
      await new Promise((resolve) => setTimeout(resolve, 1000));
      console.log("pre async");
    },
    () =>
      new Promise((resolve) => setTimeout(resolve, 1000)).then(() =>
        console.log("pre promise")
      ),
    () => {
      console.log("pre sync");
    },
  ],
  postProcess: [
    async () => {
      await new Promise((resolve) => setTimeout(resolve, 1000));
      console.log("post async");
    },
    () =>
      new Promise((resolve) => setTimeout(resolve, 1000)).then(() =>
        console.log("post promise")
      ),
    () => {
      console.log("post sync");
    },
  ]

The above config defines 3 functions for each of preProcess and postProcess:

• One defined as an async function, which resolves after a 1-second delay
• One defined as a function that returns a promise, which resolves after a 1-second delay (the same behavior as the first function, just defined differently)
• One defined as a function that returns immediately

Expected Behavior

Based on the documentation (which states functions run in order), I expect this:

pre async
pre promise
pre sync
post async
post promise
post sync

Actual Behavior

What actually happens is this:

14:18:39.971 pre sync
14:18:40.979 pre async
14:18:40.980 pre promise
14:18:41.119 post sync
14:18:42.119 post async
14:18:42.120 post promise

(Timestamps are included above to demonstrate that the async functions finish around a second after the sync function starts, indicating they start around the same time, given the async functions' 1-second wait time.)

Root Cause

This occurs because the implementations for both properties use Promise.all on a mapped array which has already immediately invoked each function up-front. To preserve order, these functions' invocations would need to be sequentially chained instead.

Aside: It is worth noting that the documentation itself does not seem to explicitly indicate that preProcess and postProcess support promises; it seems it was never updated when that functionality was added.

I would be interested in working on a PR to fix this if one would be accepted. (Edit: I initially had problems getting tests to run, but forcing karma to run with --browsers Firefox helped in my case, since I don't have Chrome installed on this machine.)