Pub can fail to load transformers necessary for local development

[nex3]

If a package "foo" uses a transformer from package "bar" and restricts that transformer to only run on files in "test", "bar"'s transformer won't be loaded at all. This is due to a flaw in Pub's logic for determining necessary transformers: because "bar" only runs on non-public file and isn't from the root package, pub assumes that it's not necessary. Instead, pub should check whether it's used in the root package.

This is a serious issue for the test runner: it needs to expose a transformer for its users to use, but that transformer will only be run on tests.

[nex3]

Fixed by r44876.

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Added Fixed label.

[DartBot]

This issue has been moved to dart-lang/pub#5.