libraryRoot method
The lib/ directory file belongs to, as a prefix (lib/,
packages/core/lib/), or null for a file outside every one.
Implementation
String? libraryRoot(String file) {
String? best;
for (final dir in packages.keys) {
final prefix = dir.isEmpty ? 'lib/' : '$dir/lib/';
if (file.startsWith(prefix) &&
(best == null || prefix.length > best.length)) {
best = prefix;
}
}
return best;
}