This is a Bug Report

Description

This might be considered an edge case based upon how I make use of a JavaScript configuration file but thought I would share this issue nonetheless as it tripped me up when I went to do a deploy this evening after updating my deps.

Consider the following contrived example.

config.js

const env    = process.env.NODE_ENV || 'dev';
const config = { destinationStream : `kinesis-stream-${env}` }

config._get = function () { return this; }
module.exports = config;

serverless.yml

custom :
    destinationStream : ${file(./config.js):_get.destinationStream}

cmd to reproduce

> NODE_ENV=staging serverless package

Running the above cmd results in the following error.

Invalid variable syntax when referencing file "./config.js". Check if your javascript is returning the correct data.

Note this issue did not exist prior to 1.18.

I've reviewed the PR's which made up 1.18 and have pin-pointed #3888 as being the change which introduced this new behaviour.

Prior to 1.18 when a JS file was resolved it was immediately invoked and so it's context was maintained. However in #3888 it is assigned to a local variable and so no-longer has it's original execution context. ( see lib/classes/Variables#L255 )

This can be fixed by amending L255 to :

valueToPopulate = returnValueFunction.call(jsFile);

I'd be happy to submit a PR for this if you think it's worth fixing. I've since worked around it but as per above I thought I'd share the info.

Additional Data

• Serverless Framework Version you're using: 1.18
• Operating System: 10.12.5
• Stack Trace: N/A
• Provider Error messages: N/A