Prebid core: improve library support; make AnalyticsAdapter a library

[dgirardi]

Type of change

• Feature

Description of change

This:

• improves library support to automatically generate libraries and track their dependencies, so that consumers of a library simply need to import symbols from it;
• makes AnalyticsAdapter.js a library, so that it can be shared when multiple analytics adapters are included in the build.

Other information

Closes #7936
Original library PR: #8527
Minor docs update: prebid/prebid.github.io#3863

[jsnellbaker]

Checked the build file and saw the duplicate references for the analytics adapter code only appeared once, instead of dozens of time.

So this appears to working from what I can tell. Nice work :)

[mmoschovas]

lgtm

[robertrmartinez]

Looks like the libraries/analyticsAdapter/AnalyticsAdapter.js formerly known as src/analyticsAdapter.js is no longer auto included in my prebid builds using same old command as before.

Our process uses Prebid Packager https://github.com/prebid/Prebid.js-packager which I am thinking is the problem.

Since src/analyticsAdapter.js is not inside the generated rubiconAnalyticsAdapter.js, prebid packager needs to include it in the build. Guessing it does not handle libraries or something.

I'll continue to look into it.

[robertrmartinez]

Yeah, so now looks like we need to update prebid packager to correctly include the necessary library files if modules from the build include it.

I see analyticsAdapter.js is output now after this PR when before it was not included in output files, it was just added into analyticsAdapter files themselves.

So this needs to be included in the build.

As I think we are the only ones working with prebid packager, I will try and fix this.

[dgirardi]

@robertrmartinez the build now generates a dependencies.json that links output files to the output "library" files they need. I was unfortunately completely unaware of the packager.

[robertrmartinez]

@dgirardi No problem at all. It was written by @snapwich when he worked at Magnite for our system. And we still are using it!

Thanks for pointing out the deps file, that is nice and I will use it to make a PR to packager.

[robertrmartinez]

@dgirardi I whipped up something real quick which "solves" this. I know it could be written better / cleaner of course, but unfortunately I am slammed at the moment.

prebid/Prebid.js-packager#4

I guess we should prob get off of this prebid packager sometime maybe, but it makes our system run quicker since we do not have to run gulp build every time we build a prebid wrapper.