Analyze where dart:html came from

why_imported.dart

import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
import 'package:analyzer/dart/analysis/results.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:path/path.dart';

// Usage: dart tool/why_imported.dart path/to/entrypoint.dart
void main(List<String> args) async {
  final collection = AnalysisContextCollection(includedPaths: [current]);
  final entrypoint = args.single;

  final session = collection.contextFor(absolute(entrypoint)).currentSession;
  final lib = await session.getResolvedLibrary2(absolute(entrypoint));
  if (lib is! ResolvedLibraryResult) {
    print('Could not analyze entrypoint');
    return;
  }

  final previous = <LibraryElement, LibraryElement>{};
  final pending = <LibraryElement>[lib.element!];

  LibraryElement? culprit;
  while (pending.isNotEmpty && culprit == null) {
    final now = pending.removeLast();

    for (final import 
         in now.importedLibraries.followedBy(now.exportedLibraries)) {
      if (import.name?.contains('dart.dom') ?? false) {
        culprit = now;
        break;
      } else if (!previous.containsKey(import) && !pending.contains(import)) {
        previous[import] = now;
        pending.add(import);
      }
    }
  }

  if (culprit == null) {
    print('No dart:html import found');
    return;
  }

  final description =
      StringBuffer('dart:html was imported by ${culprit.source.fullName}\n');
  do {
    culprit = previous[culprit];
    if (culprit != null) {
      description.writeln(' which was imported by ${culprit.source.fullName}');
    }
  } while (culprit != null);

  print(description);
}