nit. .toString() is unneeded, the default behavior of interpolating a non-string into a string is to call .toString() on it anyway

why is this needed?

No need. will delete it next commit

nit. prefer final and you can replace the if/else with a ternary

this can be final

Shouldn't you be printing the buffer outside of the for loop?

If this is a bug, can you write a test that would have caught it (for example, hard-code the expected logger output, so that we can see what it should look like)? Add it to packages/flutter_tools/test/commands.shard/hermetic/analyze_project_test.dart

Yes. It should be outside, adding a test is a good idea

might as well make this public and get rid of the getter.

nit. prefer named parameters when you have more than 2

also, this constructor can be made const

Can you add dartdoc's for all the new classes you add, and any non-obvious methods? (for example .supportsProject is self-explanatory)

nit. make this a static on the ProjectValidator class. Static's are essentially global like this; however, it's a little more organized.

nit use named parameters when you have more than 2

We should be consistent with the doctor and use this unicode character: https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/doctor_validator.dart#L258

if you call buffer.writeln() here you don't need to print an extra newline in the above scope (line 53).

if you are returning early, you can un-nest the conditionals to make reading this easier:

    if (_status == StatusProjectValidator.error) {
      return 'Error: $value';
    }
    if (warning != null) {
      return '$name: $value (warning: $warning)';
    }
    return '$name: $value';

do we need to await one before starting the next, or are these safe to run concurrently?

Also, can we use a spinner like in the doctor, so that the user knows the tool is still running?

https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/doctor.dart#L341

Also maybe we should catch exceptions and mark them as crashed, as we do in the doctor: https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/doctor.dart#L350

i think you can mark this as final

Don't re-use the same filesystem between tests

I'm thinking you probably shouldn't re-use the logger between tests?

Can we get rid of this extra line?

I don't think we should add this until it's ready to be used.