Async plugins don't work as filters

[dorongutman]

Describe the bug

When I have a plugin that's async (meaning it uses callback(error, response) for sending the response and/or error, there's a Warning: Syntax warning: expected a boolean or a numeric value under if in myAutomation and the filter is resolved as truthy.

To Reproduce

Here's a reproduction repo with example PR - dorongutman/reproduce-gitstream-main#3

There are 4 plugins: two that return a true response, and two that return a false response. In each pair, one is a sync plugin and one is an async plugin.
You can see in this github actions run that the 2 async plugins triggered the above warning and that both were treated as truthy in the filter.

Expected behavior

An async plugin needs to work.

Example async plugins

// file at .cm/plugins/filters/falserAsync/index.js
module.exports = {
    async: true,
    filter: async (input, callback) => {
        return callback(null, false);
    }
};

usage in a gitstream.cm file:

automations:
  falserAsync:
    if:
      - {{ "" | falserAsync }}
    run:
      - action: add-label@v1
        args:
          label: "falser-async"
          color: "b60205"

Screenshots

[MishaKav]

Thanks for reporting this issue! You've identified an important limitation in our evaluation engine.

The issue occurs because our evaluation engine doesn't always execute async functions during the initial rendering phase. When async functions are used in if statements, they may not be properly evaluated, leading to the warning you're seeing.

Solution: To ensure async functions are executed immediately when used in conditional statements, add the immediate: true property alongside async: true in your function definition:

module.exports = {
    async: true,
    immediate: true,  // Add this property
    filter: async (input, callback) => {
        return callback(null, false);
    }
};

The immediate: true property tells the evaluation engine to execute the async function during the rendering phase rather than deferring it, ensuring proper boolean evaluation in if statements.

This should resolve both the syntax warning and the incorrect truthy resolution you're experiencing.

[vim-zz]

Also added to docs: #782