Prebid core: fix native trackers for Prebid Server; simplify native ORTB logic

[dgirardi]

Type of change

• Bugfix

Description of change

A followup to #8086, this:

• fixes several things about how native trackers are handled. The original intent was to offload their processing to the PUC (Native ortb prebid-universal-creative#150); since that has not been merged, trackers do not work for adapters that reply in native ORTB (currently that is just the Prebid Server adapter). However there are other problems with that approach - mixing of URLs and markups; as well as a long standing problem with confusing arrays and strings in the legacy javascriptTrackers .
• adUnits (and bid requests derived from it) now have a nativeOrtbRequest property that adapters can use instead of manually converting bidRequest.nativeParams (or bidRequest.mediaTypes.native). I think this makes more sense because all requests derived from an ad unit will result in the same ORTB native request object.
• native rendering now retrieves the native request from the adUnit, instead of separately associating each request with the native request.

This is also in preparation of #8738, where I plan to re-use this logic for all ORTB adapters (including the PBS adapter, which currently duplicates a lot of the logic).

FYI @bretg @musikele; with this, the guidance to adapters that want to deal with native in ORTB should be to pick bidRequest.nativeOrtbRequest (instead of convertLegacyNativeRequestToOrtb(validBidRequests)).

[patmmccann]

@jbartek25 fyi

[jbartek25]

@dgirardi Apologies for a question not directly related to this PR but I'm getting confused. I'm the maintainer of the Improve Digital bid adapter. We recently migrated our adapter to oRTB and so I was eagerly waiting for #8086 (thank you for all the effort) to be merged. Now as part of #8701 I already started implementing logic to allow publishers to override the default native params via nativeParams.ortb and see that this PR changes nativeParams to nativeOrtbRequest and there's bunch of other related PRs open (including the docs PR prebid/prebid.github.io#3497). I'm wondering, at which point can the bidder adapters start adopting ortb native? I thought it was after #8086 got merged but now I'm not so sure. Please advise.

[musikele]

One issue and a question.

• in file native.js at line 483 instead of

    if (key in NATIVE_KEYS_THAT_ARE_NOT_ASSETS) continue;

change to

    if (NATIVE_KEYS_THAT_ARE_NOT_ASSETS.includes(key)) continue;

This is a leftover bug by me.

---

Regarding the trackers: I see that trackers are fired in PUC , file nativeORTBTrackerManager.js... how is it supposed to work? Were your changes only related to legacy behaviour?

[musikele]

@jbartek25 before releasing any change I'd wait for the PUC to be relased and the documentation to be published...

[dgirardi]

@musikele, with the PUC version that's currently out, it would send a message that triggers fireNativeTrackers on the Prebid side - which with this, should work again for native ortb responses. (I don't know, however, if the exising PUC native tracker logic is sound).

The PUC native PR wanted to move that logic to the PUC. For that to work it had to be merged & shipped first I think (it's something I missed when we were discussing the rollout). If you still want to go that route you would need to copy the logic in this PR over, it does not seem worth it to me - considering also that apparently some publishers prefer to not use the PUC (and do this instead).

The PUC PR needs updates either way - it should fix the native tracker logic (like in here), or remove it.

[dgirardi]

@jbartek25 there's also #8738 - and I am looking for adapters like yours to convert with it! (example of what I am doing with them, and documentation). It would automatically support native with the same logic used by the Prebid Server adapter, including this PR and #8086, as well as any other future updates.

If you trust your test suite, or are willing to help me with verification in that PR, I can include your adapter - I am hoping to find a couple so that they can work as reference implementations.

[jbartek25]

@dgirardi

If you trust your test suite, or are willing to help me with verification in that PR, I can include your adapter

Yes, sure :-). Our adapter's test suite is pretty extensive + I can help with testing as needed.

[musikele]

Tested with jstracker, eventtracker and everything should work for legacy native (that is the one everybody's using).
In general, you cannot use mediatype.native.ortb until the PUC changes are adapted to support ortb responses in templates.