Handling missing packages in specific functionalities

[leeuwis]

The following functionalities need specific packages to be installed:

• Data Transfer Objects: validateObject requires class-validator and class-transformer (if ValidationPipe is used)
• Route Matching: findRoute requires path-to-regexp (if non-empty paths are used in the method decorators)

At the moment this is not handled explicitly, resulting in unexpected behaviour (if someone didn't fully read the docs).

Should we:

• Install the packages by default (makes is less "light", but does that matter since it's server side)
• Throw an error (crash) when one of the functions is used without the package(s)
• Display a warning with a link to the corresponding docs when one of the functions is used without the package(s)

Let me know your thoughts 🤙

[ggurkal]

I think we should display a warning message. About the other options:

Install the packages by default

We shouldn't install packages by default because it'll have an impact on the cold start of lambda functions.

Throw an error (crash) when one of the functions is used without the package(s)

If we crash, the function will go into a loop of restart -> crash -> restart I believe.

[leeuwis]

@ggurkal implemented the warnings in this PR.

Regarding the error option, we could throw an InternalServerErrorException in the validateObject handler. This wouldn't result in a crash loop, it would return a HTTP exception when a route using the ValidationPipe is called. What are your thoughts on this?

[ggurkal]

I've done some checks and the following is only valid for class-validator (and maybe class-transformer):

This functionality will be useful when a dependency is in devDependencies rather than dependencies, in that case build process will succeed but the production build won't even start.

So, my question is: does it make sense to add some extra functionality for development mode, like check if the package is in devDependencies while it should be in dependencies and warn the dev as early as possible?

If you want to test, move class-validator into devDependencies and:

$ yarn build && rm -rf node_modules && yarn --production && yarn start