Pin @types/node to 6.0.42 for yelb-ui

[alexpulver]

Latest versions of Node.js lead to the following exception when building yelb-ui Docker image:
node_modules/@types/node/index.d.ts(20,1): error TS1084: Invalid 'reference' directive syntax.

Pinning to 6.0.42 version (instead of ^) solves the issue.

[mreferre]

Thanks Alex for opening the PR. In the past I have solved similar problems by elevating the node version of the container. I am no node expert but I'd rather try to solve it that way Vs pinning a library to a specific version. I need to do some research around this.

[alexpulver]

In this case elevating Node.js version is exactly what caused the exception. The application code uses a reference directive syntax somewhere (I didn't capture the full exception, but it is easily reproducible). This directive is part of @typescript module, which is pinned to ~2.2.0 patch versions in package.json. My understanding is that this directive no longer recognized by latest Node.js version. Bumping @typescript module version breaks other parts of code, because it relies on the module interface, which significantly changed since 2.2.0.

Usually pinning is a best practice for reproducible builds (Why pin dependencies? provides a good explanation in my opinion). Explicit dependencies update provide a controlled path to testing first and upgrading later (e.g. Dependabot pull requests model).

[mreferre]

Oh absolutely. I don't disagree with you. I actually have this in the README as a bullet of the known issues & limitations section:

"While I am trying to explicitly declare container tags and modules versions moving forward, there is a chance that if you try > to build your own containers from the Dockerfile provided and/or install the project on a cloud instance, the output may be > diverging from one setup to another. Generic commands such as apt-get update, npm install and gem install sinatra may >lead to different versions of code and modules being pulled at build and setup times."

I just wanted this to be more pro-active than reactive like here (this is a message to self, not to you - thank you a ton for ringing the bell).

LGTM