warlock.flow

Josh David Miller edited this page May 10, 2014 · 1 revision

warlock.flow

The API for the magic of Warlock: collections of mergeable streams called "flows".

Methods:

Flow Instance Methods:

warlock.flow( name, [options] ) : Flow

Creates a new Flow or fetches an existing one.

If options is specified, a new flow is created, passing the name and options directly to the Flow constructor; however, altering flow definitions is not yet implemented, so if the flow already exists, an error will be thrown. See the Flow class for more information on the available options.

Returns the flow.

warlock.flow.all() : Array

Returns an array of all defined flows.

This should not be used by plugins as they are read in no defined order, so this list is almost guaranteed to be incomplete until after Warlock finishes bootstrapping.

warlock.flow.getMetaTasks() : Object

Returns an object where its properties are the names of tasks and its values are arrays of the flows that should run during said tasks. Populated from options.tasks when a flow is created.

warlock.flow.getFromTaskName( taskname ) : Flow

Gets a flow based on its task name in Warlock, or undefined if no such flow exists.

warlock.flow::constructor( name, options ) : Flow

The Flow constructor.

The name of the flow is used throughout Warlock and must be unique. The options passed configure the behavior of the flow. options must contain a source value and either an options.dest or an options.merge value must be specified so the stream has somewhere to start and somewhere to end up.

Options

source: The stream must originate somewhere. This can be either: (1) a string or an array of string globbing patterns to be read in; or (2) a function that returns a readable stream.

source_options: Options to be passed to vinyl-fs's src method to configure how the Vinyl file objects are created from the source globs. This is ignored if options.source is a function.

dest: A string path to which the files at the end of the stream should be written.

merge: To build isolated, stand-alone, reusable, and composable flows, it can be helpful to be able to merge a stream in with another flow. For example, the webapp spell defines a set of flows for working with CSS, JavaScript, HTML, and static assets; if you want to include LESS or CoffeeScript functionality as well, those spells can lint and process the source files and request that they be merged into the upstream webapp flow. Warlock will automatically handle task dependencies.

A merge is a string directive specifying the type of merge, the target of the merge, and the priority at which it will merge in the format: type::target::queue. At present, only two types of merges are supported: queue and flow. A flow type merge essentially adds a new stream at the specified priority to the target flow at runtime, wherein it merges the last stream of this flow into the stream of the other flow. In the CoffeeScript example, we want it to merge into the scripts-to-build flow after all the JavaScript linting (priority 12) but before the JavaScript file paths are saved for use in the template (priority 100); to ensure it occurs after anything any other task might be merging into that flow too, we pick a relatively high number. Thus, the merge directive is flow::scripts-to-build::90.

tasks: An array specifying the tasks during which this flow should run. These tasks must be defined elsewhere. This is usually used by plugins to aggregate a set of flows to run with one command, e.g. warlock build can run five different flows if [ "build" ] is specified under the options.tasks for each of the five flows. Plugins can work together as well; a plugin (or you, for that matter!) can add your own flows to tasks.

depends: By default, every task in Warlock that can run concurrently does. So a task comprised of five flows could see all flows running at the same time. But sometimes, a flow shouldn't start until another task or flow has completed. An task name or an array of task names can be specified here to ensure they complete before this flow starts. Warlock automatically handles this where it can; for example, if task A merges into task B, Warlock will automatically set B to depend on A, and so such a dependency need not be specified here. Flows should, where possible, be isolated components.

clean: Whether or not the path specified in options.dest should be deleted from disk prior to running this flow. Defaults to false. If options.dest is not specified, this is ignored.

watch: Whether or not this flow should have a watcher set up. Defaults to true. When watching is enabled, when the any files identified by the options.source globs change, this flow is executed, preceded by any dependencies and followed by any merge targets. By default, only files that have changed are piped through the streams, so that if a single JavaScript file changes, we do not throw all JavaScript files through the flow.

Watching mergeable flows can be a little tricky. When the simple case leads to challenges, a configuration object can be passed instead of the simple boolean. For example, it is not always desirable for a flow to only process changed files on watch; sometimes we need to process them all (e.g. if they get concatenated). We can disable this functionality by passing { all: true }.

This option is ignored when options.source is a function, as there is nothing to "watch".

warlock.flow::add( priority, name, streams, options ) : Flow

Adds a new stream or streams to which the data will be piped at the specified priority/order in the flow.

When the flow runs, the stream (initially from options.source) is piped to each subsequent stream added to the flow, sorted on the priority specified. It returns the flow itself, so it's chainable. For example, with the following definitions:

warlock.flow( "myFlow" )
  .add( 10, "task1", task1 )
  .add( 50, "task2", task2 )
  .add( 30, "task3", task3 )

Running the flow will essentially do this (highly simplified):

source
  .pipe( task1() ) # priority 10
  .pipe( task3() ) # priority 30
  .pipe( task2() ) # priority 50
  .pipe( dest )

The streams argument can either be an array of streams or a function that returns one or more streams. The latter is by far the most common use case, following the same convention used in other stream-based frameworks and applications, like Gulp. Speaking of Gulp, any Gulp plugin should be easily used in any Warlock flow:

coffee = require "gulp-coffee"
warlock.flow( "coffee-to-build" ).add 50, "coffeescript-compile", coffee

The stream gets created when it's needed by calling the coffee function, passing in a configuration from the Warlock config based on the name of the stream. If we want to pass in some configuration options, we can just add them to the global config, so the stream definition remains clean and fully reusable. The CoffeeScript spell comes with the following default, which can be easily overridden by your own configuration:

{
  "tasks": {
    "coffeescript-compile": {
      "bare": true
    }
  }
}

TODO(jdm): To minimize clashing, it should be based on both the flow and the stream names, e.g. tasks.coffee-to-build.coffeescript-compile.

Because of the vast assortment of Gulp plugins, there is no need to write your own most of the time (though it's fairly straightforward when you need to).

On rare occasions, a simple writeable stream won't due; in that event, you can pass { raw: true } as the options parameter. Instead of running the function and piping the latest stream to the resulting stream, it will pass the latest stream to the function and expect the function to return the latest stream. As an example, spell-webapp needs to ensure correct ordering of script and style files before they are loaded into the configuration for the template to automatically insert. Since streams are inherently asynchronous, we cannot use the standard method. Instead, we can do this:

warlock.flow( 'scripts-to-build' )
.add( 100, 'webapp-sort', ( options, stream ) ->
    stream.collect()
      .invoke( 'sort', [ util.sortVendorFirst warlock.config "globs.vendor.js" ] )
      .flatten(), { raw: true } )

This is a very advanced usage, but the meaning of the code is fairly straightforward: take the stream; collect all data written to it into an array; invoke the sort method on the array, passing in the sorting algorithm; and return a new stream that emits the re-ordered results.

warlock.flow::run()

The method that kicks off the run of a particular flow. This should never be called by the user.

warlock.flow::shouldBeCleaned() : Boolean

Whether or not this flow needs a clean task.

warlock.flow::shouldBeWatched() : Boolean

Whether or not this flow should be executed whenever its source changes. This only takes into consideration whether this flow is configured to handle a watch, not whether a watch is currently running.

warlock.flow::getDependencies() : Array

Retrieves the list of dependencies on this flow. From options.depends as well as any flows that Warlock is able to determine must run first, such as those that merge into this task.

warlock.flow::getStreams() : Array

Retrieves the set of streams/steps attached to this flow. Excludes merges.

warlock.flow::getSources() : Array|Function

Gets the sources specified at flow creation, processed as a template by warlock.config.process, or the function provided as options.source.

warlock.flow::getTasks() : Array

Gets the names of the tasks during which this flow has requested to run. From options.tasks.

warlock.flow::getTaskName() : String

Get the name of the task under which this flow will be listed. As of this writing, it is "flow::".

warlock.flow::addToQueue( queue, stream )

Adds an external stream to the specified merge queue, creating the merge queue if it doesn't exist. This is used internally to handle merging.

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