writeCanRead function
A build behavior which writes either 'true' or 'false' depending on whether
assetId
can be read.
Implementation
BuildBehavior writeCanRead(AssetId assetId) =>
(BuildStep buildStep, Map<String, List<String>> buildExtensions) =>
_copyToAll(buildStep, buildExtensions,
readFrom: (_) => assetId,
read: (buildStep, assetId) async =>
'${await buildStep.canRead(assetId)}');