Dart compiler should offer suppression of info messages

[timsneath]

We should suppress the output when the compile isn't something the user asked for - e.g. where running any flutter command requires compiling flutter_tools. This could be done e.g. with an undocumented --silent flag that can be used by Flutter.

See flutter/flutter#74366 for the current output.

[timsneath]

@mit-mit to make sure this lands, given the tight timescale for the next beta cut-off.

[mit-mit]

@johnniwinther is looking at adding a new verbosity option to the CFE, after that we'll need a flag in the VM to pass on that option, cc @bkonyi

[johnniwinther]

The plan is to add a --verbosity option with values error, warning, info, and all similar to dart-lang/pub@97555de with the default value all.

@mit-mit Do you agree?

[mit-mit]

sgtm!

[vsmenon]

Marking as a P2.

What's the expected timeline for a fix? It'd be nice to get this in pre cut, but I don't think we need to block. It should be a low risk cherry pick if needed. FYI - @franklinyow

[johnniwinther]

I expect to have CL for the CFE implementation ready today. This includes handling of the dart compile js, dart compile exe and dart compile aot-snapshot commands.

[johnniwinther]

The CFE CL is in the pipeline: https://dart-review.googlesource.com/c/sdk/+/180566