Handle undefined environment variables in resolveJoins

[AlexHayton]

Suggested fix for #1048 - tested locally and it works for me.
I also added a test suite for env var handling

Fixes the following exception:

Debug: internal, implementation, error
    TypeError: Cannot read property 'Fn::Join' of undefined
    at /Users/alexhayton/personal/stablemaster/lambda/node_modules/serverless-offline/dist/utils/resolveJoins.js:17:28
    at Array.forEach (<anonymous>)
    at resolveJoins (/Users/alexhayton/personal/stablemaster/lambda/node_modules/serverless-offline/dist/utils/resolveJoins.js:15:28)
    at new LambdaFunction (/Users/alexhayton/personal/stablemaster/lambda/node_modules/serverless-offline/dist/lambda/LambdaFunction.js:154:56)
    at LambdaFunctionPool.get (/Users/alexhayton/personal/stablemaster/lambda/node_modules/serverless-offline/dist/lambda/LambdaFunctionPool.js:93:24)
    at Lambda.get (/Users/alexhayton/personal/stablemaster/lambda/node_modules/serverless-offline/dist/lambda/Lambda.js:60:88)
    at hapiHandler (/Users/alexhayton/personal/stablemaster/lambda/node_modules/serverless-offline/dist/events/http/HttpServer.js:511:82)
    at module.exports.internals.Manager.execute (/Users/alexhayton/personal/stablemaster/lambda/node_modules/@hapi/hapi/lib/toolkit.js:41:33)
    at Object.internals.handler (/Users/alexhayton/personal/stablemaster/lambda/node_modules/@hapi/hapi/lib/handler.js:46:48)
    at exports.execute (/Users/alexhayton/personal/stablemaster/lambda/node_modules/@hapi/hapi/lib/handler.js:31:36)
    at Request._lifecycle (/Users/alexhayton/personal/stablemaster/lambda/node_modules/@hapi/hapi/lib/request.js:312:68)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at Request._execute (/Users/alexhayton/personal/stablemaster/lambda/node_modules/@hapi/hapi/lib/request.js:221:9)

To reproduce, simply define something in provider.environment which isn't set in your local shell:

provider:
  environment:
    MY_ENV_VAR: ${env:MY_ENV_VAR}

[matthewberryman]

Can confirm this fixes #1048 for me.

Environment
serverless version: v1.75.1
serverless-offline version: this PR
node.js version: v14.5.0
OS: Ubuntu 20.04 (aarch64)

[bryantbiggs]

@dherault can we get this in as 6.5.1 please? Theres also #1053 which this would supersede

[AlexHayton]

Is there anything else I need to do for this PR to get accepted?

[AlexHayton]

I've also added a test suite for this. 🎉
Checked against master branch, it is failing there (as expected). But passing here! @dherault let me know if you would like me to add more test cases!

[connorads]

I'm guessing that @dherault is away on holiday, like a lot of France in August 🌞🇫🇷

[connorads]

If anyone needs a temporary fix you can reference a hotfix package.

@connorads/serverless-offline which is v.6.5.0 with added fix from #1053.

package.json

  "devDependencies": {
    "@connorads/serverless-offline": "^6.5.0",
  },

serverless.yml

plugins:
  - "@connorads/serverless-offline"

[dherault]

Thanks @AlexHayton for this amazing fix.
@connorads I was indeed in holidays nice catch!

[bryantbiggs]

thank you @dherault !