Why Is Rake Not Able to Invoke Multiple Tasks Consecutively

Why is Rake not able to invoke multiple tasks consecutively?

The issue is that invoke only invokes the task if it is needed. Running rake --trace shows:


(in /tmp/ruby)
** Invoke default (first_time)
** Execute default
** Invoke list (first_time)
** Execute list
Hello level 1
** Invoke list
** Invoke list

So you can see it's trying to invoke the task :list two more times. But one thing you can do is to change the body of the main task to:

task :default => [] do
Rake::Task[:list].invoke 1
Rake::Task[:list].reenable
Rake::Task[:list].invoke 2
Rake::Task[:list].reenable
Rake::Task[:list].invoke 3
end

then the :list task is needed again and it correctly prints out all 3 statements.

The cleaner way to do it is to use execute rather than invoke:

task :default => [] do
Rake::Task[:list].execute 1
Rake::Task[:list].execute 2
Rake::Task[:list].execute 3
end

task :list, [:level] => [] do |t, args|
puts "Hello level #{args}"
end

That changes your puts statement to use just args rather than args.level for some reason. There are some other caveats with using execute over invoke described in the link above.

Running Rake tasks in RSpec multiple times returns nil?

The Rake docs say invoke will only run the task if it's "needed". The following was pulled from another SO answer and might help clarify:

  • Rake::Task["build"].execute always executes the task, but it doesn't execute its dependencies

  • Rake::Task["build"].invoke executes the dependencies, but it only executes the task if
    it has not already been invoked

  • Rake::Task["build"].reenable first resets the task's already_invoked state, allowing the task to then be executed again, dependencies and all.

Rake sequential tasks

maybe you want to make your reset task more explicit?

namespace :db_tasks do
desc "Rebuild development db"
task :rebuild_database, [] => :environment do
raise "Only run in development or staging" if Rails.env.production?

Rake::Task['db:drop'].execute
Rake::Task['db:create'].execute
Rake::Task['db:migrate'].execute
Rake::Task['db:seed'].execute
Rake::Task['db:test:prepare'].execute
end
end

Rails: Running more than one rake task at once?

Take a look at the rails-sh gem - it boots the Rails environment, and then presents a command line interface, so you can run your command within it. There are limitations when using it (I don't think you can change your RAILS_ENV), but for your use-case, it should be perfect.

If your commands are just rake tasks, you can use spaces to separate them, e.g.:

rake db:migrate && rake db:test:clone_structure

would become

rake db:migrate db:test:clone_structure

Testing Rake in Rails: Multiple Error Raises Silenced In Test

I can think about two solution of your problem.

But first we need to find out where is the root of the problem.

Root of the problem

Let's start with a line from your code:

Rake::Task[task].enhance ['guard_dangerous_tasks']

Comparing it with source code of Rake::Task

# File rake/task.rb, line 96
def enhance(deps=nil, &block)
@prerequisites |= deps if deps
@actions << block if block_given?
self
end

you can see, that guard_dangerous_tasks should be added to @prerequisites array. It can be easily checked:

p Rake::Task['db:reset'].prerequisites # => ["environment", "load_config", "guard_dangerous_tasks"]

Continuing with you source code.

You use invoke to execute tasks. If we pay close attention to invoke's' documentation, it states:

Invoke the task if it is needed.

Once the task is executed, it could not be invoked again (unless we reenable it).

But why should this to be a problem? We are running different tasks, aren't we? But actually we don't!

We run guard_dangerous_tasks before all tasks in our tasks array! And it's being executed only once.

Solution #1 not the best one

As soon as we know where is our problem we can think about one (not the best solution).

Let's reenable guard_dangerous_tasks after each iteration:

dangerous_task = Rake::Task['guard_dangerous_tasks']
%w[ db:setup db:reset ].each do |task_name|
expect { Rake::Task[task_name].invoke }.to raise_error(InvalidTaskError)
dangerous_task.reenable
end

Solution #2 guard_dangerous_tasks is not a prerequisite

We get better solution of our problem if we realize, that guard_dangerous_tasks should not be a prerequisite! Prerequisite are supposed to "prepare" stage and be executed only once. But we should never blind our eyes to dangers!

This is why we should extend with guard_dangerous_tasks as an action, which will be executed each time the parent task is run.

According to the source code of Rake::Task (see above) we should pass our logic in a block if we want it to be added as an action.

%w[ db:setup db:reset ].each do |task|
Rake::Task[task].enhance do
Rake::Task['guard_dangerous_tasks'].execute
end
end

We can leave our test unchanged now and it passes:

%w[ db:setup db:reset ].each do |task_name|
expect { Rake::Task[task_name].invoke }.to raise_error(InvalidTaskError)
end

But leaving invoke is a ticket for new problems. It's better to be replaced with execute:

%w[ db:setup db:reset ].each do |task_name|
expect { Rake::Task[task_name].execute }.to raise_error(InvalidTaskError)
end

Be careful with invoke!

We said above, that using invoke is a ticket for new problems. What kind of problems?

Let's try to test our code for both test and production environments. If we wrap our tests inside this loop:

['production','test'].each do |env_name|
env = ActiveSupport::StringInquirer.new(env_name)
allow(Rails).to receive(:env).and_return(env)

%w[ db:setup db:reset ].each do |task_name|
expect { Rake::Task[task_name].invoke }.to raise_error(InvalidTaskError)
end
end

our test will fail with original reason. You can easily fix this by replacing the line

expect { Rake::Task[task_name].invoke }.to raise_error(InvalidTaskError)

with

expect { Rake::Task[task_name].execute }.to raise_error(InvalidTaskError)

So what was the reason? You probably already guess it.

In failing test we invoked the same two tasks twice. First time they were executed. The second time they should be reenabled before invokation to execute. When we use execute, action is reenable automatically.

Note You can find working example of this project here: https://github.com/dimakura/stackoverflow-projects/tree/master/31821220-testing-rake

How to write task which run multiple tasks with args?

You can use Rake::Task["<your_task>"].invoke(<params>).

Eg: Rake::Task["db:migrate"].invoke.

invoke runs the dependencies as well unlike execute. If the task has already been invoked, you'll need to do use reenable ie Rake::Task["<your_task>"].reenable

Asking questions in rake tasks


task :input_test do
input = ''
STDOUT.puts "What is the airspeed velocity of a swallow?"
input = STDIN.gets.chomp
raise "bah, humbug!" unless input == "an african or european swallow?"
end
task :blah_blah => :input_test do
end

i think that should work



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