TEvent::fill() Fix, master branch (2020.10.20.)

This is a manual cherry-pick of !37405 (merged). (The copyright messages at the top of TEvent.cxx differ between 21.2 and master. That caused an issue for the automatic cherry-pick...)

As described in the original MR, this is meant to fix ATLASG-1555. An issue with xAOD::TEvent::fill() not writing out all dynamic branches of a container correctly. As found by @robouque.

added bugfix label

WARNING: big files (>100K) are found in the changeset

136K in file Control/xAODRootAccess/Root/TEvent.cxx

This merge request affects 1 package:

• Control/xAODRootAccess

Adding @akraszna ,@ssnyder as watchers

added Core master review-pending-level-1 labels

CI Result FAILURE (hash d1d131bc)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 22127]

Those failures are unrelated to this MR, but this was the final straw. I finally spent the time to fix them in !37443 (merged). (Didn't want to extend the scope of this MR by lugging those fixes in here as well.)

So I guess we should wait for !37443 (merged) to be merged in before this one would be...

Alright let's hope it will finish soon!
So that this one could be added as well.
Thanks a lot Attila

Dear Attila,
I saw the test for the MR !37443 (merged) were successful.
Would it be possible, please, to launch again tests for this MR as it failed yesterday?
I am just not sure if MR !37443 (merged) was already merged.
Thanks in advance,
Best regards,
Romain

Hello, I can launch CI again, but also not sure if it helps now because MR !37443 (merged) is not merged yet (L1).

Jenkins please retry a build

WARNING: big files (>100K) are found in the changeset

136K in file Control/xAODRootAccess/Root/TEvent.cxx

This merge request affects 1 package:

• Control/xAODRootAccess

Adding @akraszna ,@ssnyder as watchers

You had it right Damian... You should not have re-launched the CI yet. Indeed, we need to wait for !37443 (merged) to be merged in first...

Sorry, but this can't hurt, right?

No. This is by no means the end of the world. I just wanted to set everybody's expectations, that this will fail in the CI tests in the same way as yesterday's build...

Sure, thanks.

Ah sorry for that I thought the other MR was already added :/

In fact it was approved but not merged yet, we have to wait for it.

CI Result FAILURE (hash d1d131bc)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 22170]

Hello @dgil,
I think now the MR has been merged,
Could you please launch again the test?
Sorry to ask I don't know how to do it myself and don't know if I am allowed to do it
Many thanks in advance