Handler.js can return a promise

[padiazg]

Signed-off-by: Patricio Díaz padiazg@gmail.com

Index.js can handle is handler.js returns either a final value or a promise

Description

Added code to index.js tu verify if the value returned by handler is a promise, if so first resolves it to get the final value to return.

Motivation and Context

Many users ask for using promises or async/await to handle asynchrony.

• I have raised an issue to propose this change (required)

Which issue(s) this PR fixes

Fixes #92

How Has This Been Tested?

For normal behavior, handler returning final value:

While in the templates folder created a function with

$ faas-cli new promise-test --lang node

Deployed with

$ faas-cli up -f promise-test.yml

Checked that it works using Portal

For cheking when handler returns a promise:

At handler.js, commented the actual module.exports and uncommented the sugested one that returns a promise.

Deployed again and test with Portal

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.

[lucyllewy]

You're missing a branch where the result is not a Promise. I think that will break backwards compatibility where someone updates their existing function to the new template or they write a new function the old way expecting it to still work.

[padiazg]

I don't think so. The portion of code responsible of returning the result of the function is now packet in cb, which is passed to handler. If you are running a "legacy" function cb will be called, the result sent to the GW and all ends there.
But if in turn you are running a function that returns a Promise, it will be "unresolved" in index.js and that's why we check if it's a Promise, and resolve it to return a result.