Using Prebid.js as npm dependency

[snapwich]

Type of change

• Feature
• Refactoring (no functional changes, no api changes)

Description of change

This updates the code base to be useable directly from npm as a library within another application. The README is updated with instructions for using Prebid.js with both Babel 6 and 7. After implementing the proper babel-loader within the external application, Prebid.js can be used like so

import prebid from 'prebid.js';
import 'prebid.js/modules/rubiconBidAdapter'; // imported modules will register themselves automatically with prebid
import 'prebid.js/modules/appnexusBidAdapter';
prebid.processQueue();  // required to process existing pbjs.queue blocks and setup any further pbjs.queue execution

prebid.requestBids({
  ...
})

This updates the local Prebid.js build to the latest version of Babel. This required refactoring to ES6 modules for many of the files (no mix-matched commonjs and es6 imports/exports).

It also replaces the string-replace-webpack-plugin with a Babel Plugin for doing all the global search and replacing for things such as the $$PREBID_GLOBAL$$.

Other information

ES6 modules affect some of the capabilities of sinon stubbing. To allow stubbing for some features, in utils for example, an internals export was added to allow stubbing features (similar to how commonjs exports object was being used). I investigated using something like babel-plugin-rewire to do stubbing, however it's incompatible with our instanbul setup and fixing it to work correctly would be an even larger refactor; however, it might be worth investigating in the future.

Going forward, any build features that we would added with Gulp or Webpack should probably be implemented as Babel Plugins to maintain compatibility for applications using Prebid.js directly from npm. It might be worthwhile creating another repo that pulls in Prebid.js as an npm dependency and tests functionality to avoid breaking integrations.

All file imports withinsrc and modules files were updated to use relative pathing. This is required since any application pulling in Prebid.js will most likely not have the same webpack resolver to properly locate resources. Any new pull-requests adding features should use relative paths for any files within src or modules. It's still fine to use the webpack resolver for imports within test.

I updated the README to mention that using this feature requires Prebid.js 1.38.0+, so it'd be nice to add this in the next release so that is accurate.

Closes #1853

[mkendall07]

This pull request introduces 1 alert when merging f5b8f32 into c07e60d - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

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Comment posted by LGTM.com

[mkendall07]

LGTM. Major props @snapwich !