invoke local --watch is not working

[Luo Gang]

This is a Bug Report

Description

• What went wrong?
  start with
  sls invoke local --function some-function --watch
  when change the code, it recompiles the code, but it still seems invoke the old compiled result

• What did you expect should have happened?
  It should run the latest compiled result just as what the documentation says.

• What was the config you used?

service: some-service

plugins:
  - serverless-webpack
  - serverless-offline

custom:
  webpack:
    webpackIncludeModules: true

package:
  individually: true

provider:
  name: aws
  runtime: nodejs6.10
  stage: dev
  region: us-east-2

functions:
  some-function:
    handler: some-function/handler.handler

• What stacktrace or error message from your provider did you see?
  No errors, the output is like this
  

the second time it should output 5 instead of 6 because the code has changed.

Similar or dependent issue(s):

Additional Data

• Serverless-Webpack Version you're using: 5.1.0
• Webpack version you're using: 4.1.1
• Serverless Framework Version you're using: 1.26.1
• Operating System: macOs High Sierra 10.13.3
• Stack Trace (if available):

[Luo Gang]

I used to use --watch with sls offline start --watch. It worked. This time I don't have a http event, so it's invoked directly, but it does not work.

[Frank Schmid]

@crysislinux Thanks for reporting 👍

It seems that Webpack 4 changed something with its watch mode. This comment #279 (comment) also points to that because for @stormit-vn it looks like the issue with watch happens with serverless-offline too.

This should be investigated, to see what exactly changed on Webpack's side, so that we can implement a proper fix.

[Frank Schmid]

Just to be completely sure. Can you try with serverless-webpack 5.0.0 and Webpack 3, to see if it is really a change in Webpack 4 that triggers the problem? If yes, we should put "Webpack 4" into the issue subject.

[Frank Schmid]

Further question: Did you set the new Webpack mode option to "development" for local invocations in your webpack.config? This enables debug functionality for the built output.

mode: slsw.lib.webpack.isLocal ? "development" : "production"

[Luo Gang]

@HyperBrain Thanks for the quick response.

I tried with the following combinations

1. serverless-webpack 5.1.0 webpack 3
2. serverless-webpack 5.1.0 webpack 4
3. serverless-webpack 4 webpack 3

It seems that sls invoke local -f some-function --watch does not work for all of the combinations.

But it do work with sls offline start --watch, by "work" I mean when send a http request to the endpoint, it will response with the latest code ("good" changes to "good1").

And yes, I have this in webpack.config.js

mode: slsw.lib.webpack.isLocal ? "development" : "production"

[Frank Schmid]

Ok. Then it looks like a general issue restricted to invoke local --watch. This is a bug then and has to be fixed.

[Frank Schmid]

The problem might be due to the require cache. Invoke local requires our handler and we do not terminate the Serverless process when running in watch mode. On a watch trigger, invoke local is executed again - and fetches our module under test from the require cache.

A solution would be to make sure that the invocation fetches a fresh module from disk.

[Frank Schmid]

The code of the second answer here would make it possible to remove the old cached module and let the next invocation start freshly.

https://stackoverflow.com/questions/9210542/node-js-require-cache-possible-to-invalidate

[Frank Schmid]

@crysislinux Can you check with #351 if that works for you? I did some local tests and it seems that the handler is now loaded again correctly after a watch compile.

[Luo Gang]

@HyperBrain I am really sorry that I provide some misunderstanding information. I tried again and found that the bug happens only when

package:
  individually: true  #enable this

I tried your fix, it magically fix this problem anyway 😃