This Groovy script looks simple enough:
def a = [].join()
println a
I would expect it to throw MissingMethodException because join method requires a parameter, if I'm looking at the right one, but it works just fine.
And here is the source code for that method, so the parameter is definitely not optional.
You know where it fails the way I expect it to? In Jenkins, of course.
So, why does it work? Is there some Groovy convention I don't know about? Or does it actually call a different method?
Related
I am new to Ruby and to Rails, and am trying to understand fully what I'm reading.
I am looking at some of the Rails source code, in this case action_controller/metal/instrumentation.rb.
def render(*args)
render_output = nil
self.view_runtime = cleanup_view_runtime do
Benchmark.ms { render_output = super }
end
render_output
end
I understand that *args is using the splat operator to collect the arguments together into an array. But after that, it stops making much sense to me.
I can't fathom why render_output is set to nil before being reassigned to equal super and then called with no arguments. I gather that some speedtest is being done, but coming from other languages I'd expect this to just be something more like Benchmark.ms(render_output) or perhaps Benchmark.start followed by render_output followed by Benchmark.end. I'm having a hard time following the way it works here.
But more importantly, I don't really follow why args isn't used again. Why bother defining a param that isn't used? And I mean, clearly it is getting used-- I just don't see how. There's some hidden mechanism here that I haven't learned about yet.
In this context, it is important to note how super works, because in some cases it passes implicitly arguments and you might not expect that.
When you have method like
def method(argument)
super
end
then super is calling the overridden implementation of method implicitly with the exact same arguments as the current method was called. That means in this example super will actually call super(argument).
Of course, you can still define a method call that explicitly sends other arguments to the original implementation, like in this example:
def method(argument)
super(argument + 1)
end
Another important edge-case is when you want to explicitly call super without any arguments although the current method was called with arguments then you need to be very explicit like this
def method(argument)
super() # note the empty parentheses
end
Let me try to describe you what I think this code does.
*args*
is using the splat operator to collect the arguments together into an array
that is totally correct, however they don't use it, and if you will go to master branch, they just changed it to *. Asking why it is defined and not used, I think that's question about bad design. They should have called it _args or at least like it is now just single splat *.
render_output is set to nil because of scopes, it has to be explicitly defined out block, lambda, proc in order to store value in it, otherwise its visibility will be locked only to those lambda, proc, block execution. Refer to this article
Benchmark.start. Blocks are great ruby construction. You are totally correct that speedtest is done, we can see it is just decorator for benchmark library.
source.
You are wondering why we cannot just pass it as Benchmark.ms(render_output), that's because what will be given to benchmark ms function? It will be given result, like <div> my html </div. And how we can measure this string result - no how. That's why we calling super right in this block, we want to access parent class function and wrap it inside block, so we are not calling it, we just construct it, and it will be called inside benchmark lib, and measured execution like
class Benchmark
...
def realtime # :yield:
r0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
yield
Process.clock_gettime(Process::CLOCK_MONOTONIC) - r0
end
...
end
So here we can count realtime of function execution, this is the code from original library
Let's say I'm in a really huge project and am curious how this line works:
authorize! :read_pipeline_schedule, user_project
authorize! is supposed to be method name. Is it a private function in the class, or DSL provided from a parent block, or including, or declared in a gem? Or maybe none of them?
I was using grep to find internal code and Google for external code such as gems, however I guess it's useful if I can see the call stack of the method. puts caller is printing from the place where I am although it can not be used for analyzing the above case.
I'd like to know the best practice.
You can grep your code and installed gems and, if name is unique enough, you'll quickly locate its definition and associated usages. However, if a name is a common one, like call, then this approach is useless.
Ruby is a dynamic language and, as such, is a nightmare for static analysis. You may guess where this comes from, but you just can't know for sure.
The only way to know is runtime introspection. So, in your example, put a breakpoint right before that line
binding.pry
authorize! :read_pipeline_schedule, user_project
You'll drop out to pry shell. Now you can do
show-source authorize!
And see where exactly this method is defined.
The easiest way is to ask the method itself:
method_object = method(:authorize!)
method_object.owner
# => returns module in which the method resides
method_object.source_location
# => returns file name and line number of source code where the method is defined
Note that source_location may return nil for methods which have no Ruby source code, e.g. dynamically generated methods or methods implemented in the interpreter internals (C functions in YARV, Java methods in JRuby, etc.)
I like caller(0), caller_locations, and the ever-incredible show-source
Using MiniTest::Spec and Mocha:
describe "#devices" do
it "scopes the devices by the provided :ip_list" do
ips = 'fast tests ftw!'
ds = DeviceSearch.new ip_list: ips
Device.expects(:scope_by_ip_list).once.with(ips)
ds.devices
end
end
When I make the code work correctly, this test will fail, because calling Device.expects(:scope_by_ip_list) also stubs Device.scope_by_ip_list, and since I don't specify a .returns(Devices.scoped) or some such, it stubs out the method with nil. So, in my code which properly scopes a list of devices and then does further operations, the further operations blow up.
I don't want to have to specify a .returns parameter, though, because I totally don't care what it returns. I don't want to stub the method at all! I just want to set up an expectation on it, and leave it functioning just the way it is.
Is there a way to do that?
(To me, it seems very awkward to say something like Device.expects(:foo).returns('bar')—when I say that Model expects method, I'm not saying to stub that method! We can say Device.stubs(:foo), if we want to stub it.)
The behavior is intended and can't be changed. Look at the following post to see how it can be circumwented:
rspec 2: detect call to method but still have it perform its function
I'm attempting to test a class which makes use of the rails configuration file. I'd like to mock Rails::configuration.
I've tried things like
Rails::singleton_class.expects(:configuration).returns('result')
Rails::singleton_class.stubs(:configuration).returns('result')
How do I go about doing this?
Rails.expects(:configuration).returns('result')
Please note there was a typo in your example. The returned value must be passed using returns, not return.
Also note, Rails.configuration returns Rails.application.config. If your method doesn't use Rails.configuration directly, it might actually bypass the call and your expectation won't work.
Rails.stubs(:configuration).returns(Rails::Application::Configuration.allocate)
This answer on mocking a Net response
helped
I just started using mocha and I find it annoying that when creating a new mock object, mocha expects it to be called exactly once. I have helper methods to generate my mocks and I'm doing something like this
my_mock = mock(HashOfParameters)
All of the parameters might not get called for each test method so it will raise an error:
expected exactly once, not yet invoked
So I figured I needed to do something like this:
my_mock = mock()
HashOfParameters.each do |k, v|
my_mock.expects(k).returns(v).at_least(0)
end
This works but I was wondering if there was an easier way to do this, like changing a default configuration somewhere...
Ok, that was a stupid question... I hadn't took the time to truly understand the difference between a mock and a stub. Here's a good article that shows how it works :
http://martinfowler.com/articles/mocksArentStubs.html
So in my example, I should have been using the stub method instead of mock.