Analyzer doesn't give unnecessary_import feedback if element used only from 1 export

[SuperPenguin]

I'm doing a barrel export and notice when using only elements from 1 export files it doesn't give unnecessary_import at all.

For example if I have
a.dart

class A {}

class A2 {}

b.dart

class B {}

c.dart

class C {}

alphabet.dart

export 'a.dart';
export 'b.dart';
export 'c.dart';

and used it like so, the analyzer give feedback unnecessary_import for all a, b, c dart files

import 'package:hmmm/src/alphabet/a.dart'; // unnecessary_import
import 'package:hmmm/src/alphabet/b.dart'; // unnecessary_import
import 'package:hmmm/src/alphabet/c.dart'; // unnecessary_import
import 'package:hmmm/src/alphabet/alphabet.dart';

void something() {
  final a = A();
  final a2 = A2();
  final b = B();
  final c = C();
}

but if only element used from a.dart, it doesn't give unnecessary_import to a, only unused_import for b and c.

import 'package:hmmm/src/alphabet/a.dart';
import 'package:hmmm/src/alphabet/b.dart'; // unused_import
import 'package:hmmm/src/alphabet/c.dart'; // unused_import
import 'package:hmmm/src/alphabet/alphabet.dart';

void something() {
  final a = A();
  final a2 = A2();
  // final b = B();
  // final c = C();
}

dart --version
Dart SDK version: 2.15.1 (stable) (Tue Dec 14 13:32:21 2021 +0100) on "windows_x64"

IDE
vscode

[scheglov]

@srawlins

[srawlins]

In the second case you describe, alphabet.dart and a.dart provide the same set of "used" elements (A and A2). We consider these "redundant" imports, rather than "unnecessary."

We have not yet landed the check for redundant imports. The check is more complicated, because when two import directives provide the same set of used elements, we want to be careful about recommending which import directive to remove.

[srawlins]

Follow support for redundant imports here: #44569.