add logic to prefer prebid modules over external modules in build process

[jsnellbaker]

Type of change

• Bugfix

Description of change

Fixes #4120

This PR fixes the build problem with the Prebid.js express module reported in the above issue.

The issue only occurred when you specifically included express with the modules parameter in a build command (eg gulp build --modules=express) and because the module shared a name with one of the project's nested dependencies.

Basically this line here recognized the express module in the node_modules folder and included that path when the overall function was compiling the list of module paths to include for the build. When this path was added to the build process, it had issues trying to find its dependent packages since they were installed in the wrong locations (if we were actually using the package express directly in the project).

By adding a check to only include modules that belong to our project, it avoids adding that other file path and allows the build to proceed as normal.

[snapwich]

The only thing I'm worried about is that one of the initial requirements when I was implementing the module system was to allow modules to be pulled in from node_modules that way people could publish them and use them from npm or internal registries. It looks like this could break that?

I think we might need a system that, instead of ignoring node_modules (or in this case, things that are not in /modules), it gives priority to local /modules before node_modules. Thoughts?

[jsnellbaker]

@snapwich Thanks for the feedback; I have an idea to implement that type of logic. I'll push in the changes in a little bit.

[snapwich]

Node require with paths requires v8.9.0+ I think? (that's what the docs say, but I could swear I had issue with anything less than 10) Is that okay?

[mkendall07]

we are due for an upgrade on node anyway.

"engines": {
    "node": ">=4.0"
  },

is what package.json has. So we should update that as part of this change.

[jsnellbaker]

I updated the node version references to 8.9.0

[snapwich]

LGTM

[nanek]

Could update https://github.com/prebid/Prebid.js/blob/master/.nvmrc as well to reflect this.

[jsnellbaker]

@nanek Thanks for the suggestion. I created a follow-up PR to make this change, #4162