Make serverless-webpack more extensible

[seriouscoderone]

What did you implement:

Use PluginManager to make serverless-webpack more extensible. I am trying to create my own plugin that works with serverless-webpack, but I am unable to extend before the validation step without this change.

Closes #XXXXX

How did you implement it:

Following the advice from serverless blog on Advanced Plugin Development. Used Plugin Manager.
https://serverless.com/blog/advanced-plugin-development-extending-the-core-lifecycle/

How can we verify it:

As stated in the blog above... this will enable better extensibility.
Try to create a new serverless plugin that runs before the serverless-webpack before:deploy:createDeploymentArtifacts hook.

Todos:

• Write tests
• Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[HyperBrain]

Hi @josephleehunsaker ,

thanks for the PR (and reading my blog post 😄 ). The idea to run a separate lifecycle that can be hooked is really beneficial.
I think the approach to just "run" the webpack command is the wrong approach in this case. It would be better to declare a completely internal lifecycle as entrypoint and spawn that via plugin manager.

That offers a much better reusability of the internal steps like validation and does not invoke a complete command. I did such an implementation in the AWS deploy command which spawns it's internal lifecycle (aws:deploy:*) instead of executing a whole command.

Commands should not be run from a plugin (using "run") because they may introduce side effects special to that command.

A better solution would be to declare entrypoints webpack:validate, webpack:compile, webpack:packExternalModules and webpack:packModules and use pluginManager.spawn('....') to invoke their lifecycles. Then any plugin can hook wherever it wants to, may it be the validation, the compilation or the packaging (both levels). The public commands and hooks (webpack, before:....) will then only spawn the webpack lifecycles.

So the hookable lifecycle model would be:

-> webpack:validate:validate
-> webpack:compile:compile
-> webpack:package:packExternalModules
-> webpack:package:packModules

The webpack plugin hooks will then just spawn them like this:

-> webpack
  -> webpack:validate
  -> webpack:compile
  -> webpack:package

-> before:deploy:createDeploymentArtifacts
  -> webpack:validate
  -> webpack:compile
  -> webpack:package

-> before:deploy:function:packageFunction
  -> webpack:validate
  -> webpack:compile
  -> webpack:package

A 3rd party plugin can then hook any of these, and additionally the lifecycle events themselves are extensible, so that e.g. the webpack:package lifecycle could easily get new events if needed.
The last benefit is, that the webpack command will be independent and could even be dropped or changed, without changing anything.

[HyperBrain]

If you have "enable edits by maintainers" enabled, I will change the PR accordingly - should be straight forward (and make the unit tests test the new behavior).

[seriouscoderone]

Terrific, thx. I would appreciate it if you could get it working just right :)

I am still learning webpack plugins and serverless plugins.. so I did just enough to get the job done on my end.

I believe "enable edits by maintainers" is enabled. Let me know if you are unable to change the PR.

[HyperBrain]

@josephleehunsaker You should now be able to hook before:webpack:validate:validate or after:webpack:validate:validate. Your hook will be triggered on all occurences where the webpack plugin calls its validation (e.g. webpack command, sls package/deploy, etc).

[HyperBrain]

Can you give it a try with serverless-heaven/serverless-webpack#master and check if the standard deploy stuff still works?

[HyperBrain]

Released with serverless-webpack@4.0.0

[seriouscoderone]

Thank you so much!