Expose a `IS_LOCAL` environment variable if running via `sls invoke local`

This is a Feature Proposal

Description

When testing code locally it is sometimes important to know whether the code is ran locally or in the AWS Lambda environment. The three main reasons for us are:

• Typically we enable long stack traces for Bluebird in our code. However, if our Lambda function is ran via sls invoke local this isn’t possible and crashes with a Error: cannot enable long stack traces after promises have been created (which is caused by Serverless also using Bluebird promises). When testing code locally I have to comment out that section in our code! 😱
• Our errors are typically reported to Sentry, a third party service for error tracking. We never want to collect errors raised in a local developer environment.
• We often use a local Redis server when running code locally, as our real services are hidden inside of a VPC.

A possible workaround would be to create a dedicated “local” stage and have specific configuration for that. Certainly an option, but sometimes I’d prefer a way of quickly checking in code if my function runs locally or on AWS. Hence my suggestion: Introduce a new IS_LOCAL or SERVERLESS_INVOKE_LOCAL environment variable that is only set when the code is invoked via sls invoke local. This would be similar to the Serverless Offline Plugin which sets IS_OFFLINE.

This would enable code like this:

if (process.env.IS_LOCAL) {
  console.log("Running locally!");
}

Additional Data

• Serverless Framework Version you’re using: 1.13.2

[HyperBrain]

@DavidWells Already achieved 😸 . My PR just sets the variable in the common environment setter of the invoke local command. That will affect any AWS invoke local invocation - so to say all runtimes. There are no side effects nor downsides.

[HyperBrain]

I have also explicitly set BLUEBIRD_LONG_STACK_TRACES=1 in my env vars.

I think you have to enable long stack traces only if not running locally, because serverless invoke local already does that. So, you should put the variable assignment into a condition !IS_LOCAL.