# class Rake::Task

A Task is the basic unit of work in a Rakefile. Tasks have associated actions (possibly more than one) and a list of prerequisites. When invoked, a task will first ensure that all of its prerequisites have an opportunity to run and then it will execute its own actions.

Tasks are not usually created directly using the new method, but rather use the `file` and `task` convenience methods.

### Attributes

actions[R]

List of actions attached to a task.

already_invoked[R]

Has this task already been invoked? Already invoked tasks will be skipped unless you reenable them.

application[RW]

Application owning this task.

locations[R]

File/Line locations of each of the task definitions for this task (only valid if the task was defined with the detect location option set).

prereqs[R]

List of prerequisites for a task.

prerequisites[R]

List of prerequisites for a task.

scope[R]

Array of nested namespaces names used for task lookup by this task.

sources[W]

List of sources for task.

### Public Class Methods

[](task_name) click to toggle source

Return a task with the given name. If the task is not currently known, try to synthesize one from the defined rules. If no rules are found, but an existing file matches the task name, assume it is a file task with no dependencies or actions.

    # File lib/rake/task.rb, line 383
    def [](task_name)
      Rake.application[task_name]
    end

clear() click to toggle source

Clear the task list. This cause rake to immediately forget all the tasks that have been assigned. (Normally used in the unit tests.)

    # File lib/rake/task.rb, line 370
    def clear
      Rake.application.clear
    end

create_rule(*args, &block) click to toggle source

Define a rule for synthesizing tasks.

    # File lib/rake/task.rb, line 400
    def create_rule(*args, &block)
      Rake.application.create_rule(*args, &block)
    end

define_task(*args, &block) click to toggle source

Define a task given `args` and an option block. If a rule with the given name already exists, the prerequisites and actions are added to the existing task. Returns the defined task.

    # File lib/rake/task.rb, line 395
    def define_task(*args, &block)
      Rake.application.define_task(self, *args, &block)
    end

new(task_name, app) click to toggle source

Create a task named `task_name` with no actions or prerequisites. Use `enhance` to add actions and prerequisites.

    # File lib/rake/task.rb, line 96
    def initialize(task_name, app)
      @name            = task_name.to_s
      @prerequisites   = []
      @actions         = []
      @already_invoked = false
      @comments        = []
      @lock            = Monitor.new
      @application     = app
      @scope           = app.current_scope
      @arg_names       = nil
      @locations       = []
      @invocation_exception = nil
    end

scope_name(scope, task_name) click to toggle source

Apply the scope to the task name according to the rules for this kind of task. Generic tasks will accept the scope as part of the name.

    # File lib/rake/task.rb, line 407
    def scope_name(scope, task_name)
      scope.path_with_task_name(task_name)
    end

task_defined?(task_name) click to toggle source

TRUE if the task name is already defined.

    # File lib/rake/task.rb, line 388
    def task_defined?(task_name)
      Rake.application.lookup(task_name) != nil
    end

tasks() click to toggle source

List of all defined tasks.

    # File lib/rake/task.rb, line 375
    def tasks
      Rake.application.tasks
    end

### Public Instance Methods

add_description(description) click to toggle source

Add a description to the task. The description can consist of an option argument list (enclosed brackets) and an optional comment.

    # File lib/rake/task.rb, line 289
    def add_description(description)
      return unless description
      comment = description.strip
      add_comment(comment) if comment && !comment.empty?
    end

all_prerequisite_tasks() click to toggle source

List of all unique prerequisite tasks including prerequisite tasks' prerequisites. Includes self when cyclic dependencies are found.

    # File lib/rake/task.rb, line 74
    def all_prerequisite_tasks
      seen = {}
      collect_prerequisites(seen)
      seen.values
    end

arg_names() click to toggle source

Name of arguments for this task.

    # File lib/rake/task.rb, line 137
    def arg_names
      @arg_names || []
    end

clear() click to toggle source

Clear the existing prerequisites, actions, comments, and arguments of a rake task.

    # File lib/rake/task.rb, line 148
    def clear
      clear_prerequisites
      clear_actions
      clear_comments
      clear_args
      self
    end

clear_actions() click to toggle source

Clear the existing actions on a rake task.

    # File lib/rake/task.rb, line 163
    def clear_actions
      actions.clear
      self
    end

clear_args() click to toggle source

Clear the existing arguments on a rake task.

    # File lib/rake/task.rb, line 175
    def clear_args
      @arg_names = nil
      self
    end

clear_comments() click to toggle source

Clear the existing comments on a rake task.

    # File lib/rake/task.rb, line 169
    def clear_comments
      @comments = []
      self
    end

clear_prerequisites() click to toggle source

Clear the existing prerequisites of a rake task.

    # File lib/rake/task.rb, line 157
    def clear_prerequisites
      prerequisites.clear
      self
    end

comment() click to toggle source

First line (or sentence) of all comments. Multiple comments are separated by a “/”.

    # File lib/rake/task.rb, line 313
    def comment
      transform_comments(" / ") { |c| first_sentence(c) }
    end

enhance(deps=nil, &block) click to toggle source

Enhance a task with prerequisites or actions. Returns self.

    # File lib/rake/task.rb, line 111
    def enhance(deps=nil, &block)
      @prerequisites |= deps if deps
      @actions << block if block_given?
      self
    end

execute(args=nil) click to toggle source

Execute the actions associated with this task.

    # File lib/rake/task.rb, line 265
    def execute(args=nil)
      args ||= EMPTY_TASK_ARGS
      if application.options.dryrun
        application.trace "** Execute (dry run) #{name}"
        return
      end
      application.trace "** Execute #{name}" if application.options.trace
      application.enhance_with_matching_rule(name) if @actions.empty?
      @actions.each { |act| act.call(self, args) }
    end

full_comment() click to toggle source

Full collection of comments. Multiple comments are separated by newlines.

    # File lib/rake/task.rb, line 307
    def full_comment
      transform_comments("\n")
    end

investigation() click to toggle source

Return a string describing the internal state of a task. Useful for debugging.

    # File lib/rake/task.rb, line 345
    def investigation
      result = "------------------------------\n".dup
      result << "Investigating #{name}\n"
      result << "class: #{self.class}\n"
      result <<  "task needed: #{needed?}\n"
      result <<  "timestamp: #{timestamp}\n"
      result << "pre-requisites: \n"
      prereqs = prerequisite_tasks
      prereqs.sort! { |a, b| a.timestamp <=> b.timestamp }
      prereqs.each do |p|
        result << "--#{p.name} (#{p.timestamp})\n"
      end
      latest_prereq = prerequisite_tasks.map(&:timestamp).max
      result <<  "latest-prerequisite time: #{latest_prereq}\n"
      result << "................................\n\n"
      return result
    end

invoke(*args) click to toggle source

Invoke the task if it is needed. Prerequisites are invoked first.

    # File lib/rake/task.rb, line 181
    def invoke(*args)
      task_args = TaskArguments.new(arg_names, args)
      invoke_with_call_chain(task_args, InvocationChain::EMPTY)
    end

name() click to toggle source

Name of the task, including any namespace qualifiers.

    # File lib/rake/task.rb, line 118
    def name
      @name.to_s
    end

needed?() click to toggle source

Is this task needed?

    # File lib/rake/task.rb, line 277
    def needed?
      true
    end

prerequisite_tasks() click to toggle source

List of prerequisite tasks

    # File lib/rake/task.rb, line 58
    def prerequisite_tasks
      prerequisites.map { |pre| lookup_prerequisite(pre) }
    end

reenable() click to toggle source

Reenable the task, allowing its tasks to be executed if the task is invoked again.

    # File lib/rake/task.rb, line 143
    def reenable
      @already_invoked = false
    end

set_arg_names(args) click to toggle source

Set the names of the arguments for this task. `args` should be an array of symbols, one for each argument name.

    # File lib/rake/task.rb, line 339
    def set_arg_names(args)
      @arg_names = args.map(&:to_sym)
    end

source() click to toggle source

First source from a rule (nil if no sources)

    # File lib/rake/task.rb, line 90
    def source
      sources.first
    end

sources() click to toggle source

    # File lib/rake/task.rb, line 49
    def sources
      if defined?(@sources)
        @sources
      else
        prerequisites
      end
    end

timestamp() click to toggle source

Timestamp for this task. Basic tasks return the current time for their time stamp. Other tasks can be more sophisticated.

    # File lib/rake/task.rb, line 283
    def timestamp
      Time.now
    end

to_s() click to toggle source

Return task name

    # File lib/rake/task.rb, line 39
    def to_s
      name
    end

### Protected Instance Methods

invoke_with_call_chain(task_args, invocation_chain) click to toggle source

Same as invoke, but explicitly pass a call chain to detect circular dependencies.

If multiple tasks depend on this one in parallel, they will all fail if the first execution of this task fails.

    # File lib/rake/task.rb, line 192
    def invoke_with_call_chain(task_args, invocation_chain)
      new_chain = Rake::InvocationChain.append(self, invocation_chain)
      @lock.synchronize do
        begin
          if application.options.trace
            application.trace "** Invoke #{name} #{format_trace_flags}"
          end

          if @already_invoked
            if @invocation_exception
              if application.options.trace
                application.trace "** Previous invocation of #{name} failed #{format_trace_flags}"
              end
              raise @invocation_exception
            else
              return
            end
          end

          @already_invoked = true

          invoke_prerequisites(task_args, new_chain)
          execute(task_args) if needed?
        rescue Exception => ex
          add_chain_to(ex, new_chain)
          @invocation_exception = ex
          raise ex
        end
      end
    end

### Private Instance Methods

first_sentence(string) click to toggle source

Get the first sentence in a string. The sentence is terminated by the first period, exclamation mark, or the end of the line. Decimal points do not count as periods.

    # File lib/rake/task.rb, line 332
    def first_sentence(string)
      string.split(/(?<=\w)(\.|!)[ \t]|(\.$|!)|\n/).first
    end

format_trace_flags() click to toggle source

Format the trace flags for display.

    # File lib/rake/task.rb, line 256
    def format_trace_flags
      flags = []
      flags << "first_time" unless @already_invoked
      flags << "not_needed" unless needed?
      flags.empty? ? "" : "(" + flags.join(", ") + ")"
    end

transform_comments(separator, &block) click to toggle source

Transform the list of comments as specified by the block and join with the separator.

    # File lib/rake/task.rb, line 319
    def transform_comments(separator, &block)
      if @comments.empty?
        nil
      else
        block ||= lambda { |c| c }
        @comments.map(&block).join(separator)
      end
    end