CFE uses internal terms for sound null safety

[mit-mit]

The message here uses internal language:
"Error: A library can't opt out of non-nullable by default, when in nnbd-strong mode"
https://github.com/dart-lang/sdk/blob/master/pkg/front_end/messages.yaml#L1189

Please change this to use the external terms (sound null safety for strong, unsound null safety for weak, null safety for non-nullable):
"Error: A library can't opt out of null safety by default, when in using sound null safety"

A code search in the source shows several uses of the terms 'nndb-strong' and 'non-nullable' beyond this one.

[mit-mit]

cc @leafpetersen to confirm terminology

[mit-mit]

As for this specific error, this is the one I see when I have an app that is opened in which depends on a package which is not. I think we want to rephrase that a bit to something like:

ERROR: Cannot run with sound null safety as one or more dependencies do not support null safety. 

<list of offending dependencies>

Run 'pub outdated --mode=null-safety' to determine if versions of your dependencies
supporting null safety are available. 

[leafpetersen]

Terminology SGTM.

[johnniwinther]

Reopening for support of the more elaborate message.

[johnniwinther]

@mit-mit How do you trigger this error? I think that we need to handle the messaging based on how we trigger it; telling the user to run pub in a context where that does not apply is unhelpful.

[mit-mit]

I create an app (i.e. a package with an entry-point), and then make it depend on a second package that hasn't opted into null safety.

I have a test app you can use here: https://github.com/mit-mit/null-safety-test

[johnniwinther]

So do you see the error when you run the code with dart from the command-line, running it through your editor, or some other way of invoking Dart?

Actually, if in an editor, we should probably have dartanalyzer complain about entry-points, that, if run, would be run in sound null-safety and fail with this error.

[mit-mit]

If you change main to this, you should see it:

import 'package:test_pkg_unmigrated/test_pkg_unmigrated.dart' as pkg2;

void main(List<String> arguments) {
  // Nullable variable from unmigrated library function.
  int i6 = pkg2.bar2();

  print('Hello: $i6.');
}

$ ~/sdk/be/dart-sdk/bin/dart --null-safety --enable-experiment=non-nullable ./test_app/bin/test_app.dart

test_pkg_unmigrated/lib/test_pkg_unmigrated.dart:1:1: Error: A library can't opt out of non-nullable by default, when in nnbd-strong mode.
int bar2() {
^

[johnniwinther]

I've updated the reporting of opt-out packages in https://dart-review.googlesource.com/c/sdk/+/153964

@mit-mit please try it and see if it helps in your use case.