[Impeller] Enable logging a warning when the user opts out of using Impeller.

[chinmaygarde]

Part of flutter/flutter#144439

This does two things:

• Logs a warning when the embedder requests a non-Impeller preference when creating a shell.
• Makes the iOS embedder request a warning be logged when Impeller is not used.

I decided to put the warning logs in the shell so that as we get more opinionated about Impeller on other platforms, those platforms can just flip a flag with common log origin.

[jonahwilliams]

Two thoughts:

• If the goal is to flip the default for Q3 stable, this won't actually land in a stable release before that. From the perspective of a user on stable, they will never see this warning - you'd need to cherry pick it into the current beta. If the plan is Q4 then that is plenty of time.

• We don't currently have anyone working on migrating the rest of the g3 users. You should reach out to @xster and see if the FL@G team can follow up or if there are known blockers

[chinmaygarde]

If the goal is to flip the default for Q3 stable, this won't actually land in a stable release before that. From the perspective of a user on stable, they will never see this warning - you'd need to cherry pick it into the current beta. If the plan is Q4 then that is plenty of time.

Good point. For some reason, I thought this had to wait past the last stable release cut. Can CP if the plan is to flip the default in Q3.

We don't currently have anyone working on migrating the rest of the g3 users. You should reach out to @xster and see if the FL@G team can follow up or if there are known blockers

It was tracked in flutter/flutter#144739 but @matanlurey just unassigned himself about an hour ago since he has higher priority tasks. I can initiate the followup. Push comes to shove, I don't think we have to necessarily conflate moving to Impeller only builds in 3P with 1P because the release models are different.

[jonahwilliams]

Right, we don't have to align the two at all, but we might just want to give the fl@g folks a heads up. CPing this change seems reasonable to me.

[jonahwilliams]

LGTM

[flutteractionsbot]

Failed to create CP due to merge conflicts.
You will need to create the PR manually. See the cherrypick wiki for more info.

[jonahwilliams]

If you use the CP label that will go to the previous stable 3.19. If you want it to go to the upcoming stable you'll need to wait until the beta is released and then do a beta cp.

[chinmaygarde]

So, whatever points to flutter-3.21-candidate.0 right? I believe that is cp: beta then. I thought 3.21 was already out.

[chinmaygarde]

A bit confused about the timing. Will bring it up during the sync.

[XilaiZhang]

Yeah current stable is 3.19 and current beta is 3.21.

the tool finds current beta and current stable based on static version files that are updated when new beta/stable are created

the tool isn't aware of future branches. (because it's hard to predict which branch will be a future beta for example)

[chinmaygarde]

I need to get this into 3.21 stable. I should CP this to flutter-3.21-candidate.0 by using the cp: beta label right?

[zanderso]

The stable will be 3.22, so you want to CP this change to flutter-3.22-candidate.0. It's too soon to do that with the magic tag, but you can create the CP PR manually.

[Jasguerrero]

This is breaking google testing b/332791027

[matanlurey]

This is breaking google testing b/332791027

I commented on the bug, but any FL@G specific tooling should be routed to the FL@G team first.

The Engine/Impeller team doesn't have any idea about how these tools are built and we don't guarantee a stable stdout.