Code Transformers

This package exposes various tools to help in the creation and testing of barback transformers, as well as an interface for logging messages with constant ids for documentation purposes.

Messages and logging

This package exposes aBuildLogger class as well asMessage,MessageTemplate, andMessageId classes. These work together to provide stable error messages with ids that can be referenced in documentation.

MessageId

AMessageId is a constant definition of a message in a package. These are used to group messages with the same id or link to sections in a document.

const myId = const MessageId('myPackage', 0);

These ids should typically never change or disappear throughout the entire lifetime of a package.

Message

AMessage is a const object which has aMessageId andsnippet.

const myMessage = const Message(myId, 'my message');

MessageTemplate

TODO(jakemac): Docs on this, seehttps://github.com/dart-lang/code-transformers/blob/master/lib/messages/messages.dart

BuildLogger

TheBuildLogger class just wraps a normalTransformLogger to provide some additional functionality. You use it in the same way as aTransformLogger except that the log methods can accept aString or aMessage. This should usually be created in the first step of your transformersapply function:

apply(Transform transform) {  // If detailsUri is passed, then a link will be output with each log  // message that follows this format  // `$detailsUri#${msg.id.package}_${msg.id.id}`.  var logger = new BuildLogger(transform, detailsUri: 'http://foo.com');}

You can optionally dump out a file containing all the logs found in JSON format by calling thewriteOutput method on the logger when you are done. The output file will have the same file path as the primary input of the transformer, with an extension matching this pattern._buildLogs.$i. Thei increments starting at 0 each time that logs are output (if multiple transformers run on the same file for instance). These can all be combined into a single file later on by calling the staticcombineLogFiles(Transform transform) function.