Hi, with a custom target, how do I add some value of the payload to the dependencies ? I'm trying this :

python
class MyTarget(JvmTarget):
    
    def __init__(self,
                 payload=None,
                 spec=None,
                 **kwargs):
        payload = payload or Payload()
        payload.add_fields({
            'spec': PrimitiveField(spec),
            })

        if spec:
            self.inject_dependency(Address.parse(spec))

        super(ControllersLibrary, self).__init__(payload=payload,
                                                 **kwargs)

but I get :

Failed to instantiate Target with type <class 'MyTarget'>: 'MyTarget' object has no attribute '_build_graph'

i believe you may need to call the super constructor first

ok than is on my lack of experience in python. I thought the call to super needed to be the last thing facepalm . However it still do not work. I get something like

Exception message: Invalid target BuildFileAddress(my_target/BUILD, the_target): Failed to instantiate Target with type <class 'MyTarget'>: Cannot inject dependency from BuildFileAddress(my_target/BUILD, the_target) on the-spec:the-spec because the dependent is not in the BuildGraph.

All usage I see from

inject_dependency

is within a task rather than a target. Here should I just add the element to the

dependencies

list before passing it to the super constructor ?

if you have a

spec

arg, is there a reason you can't just add that spec to the

dependencies

when making the target in a BUILD file? what is the spec for?

MyTarget is a target that generate some code based on the spec during the gen goal and then compiles this generated code during the compile phase

oh, ok. then i think what you mentioned actually makes sense (adding that

spec

argument to the dependencies). i think you won't need to necessarily change any payload fields here then, and you could just add an entry to

dependencies

before calling the super constructor.

so I naivelly tried this :

ds = kwargs.pop('dependencies', [])
ds.append(spec)
kwargs.update({'dependencies': ds})

but it bakfired heavily. Do you know how I can add an entry to

dependencies

backfired how? it may be that the

dependencies

arg is a list of a different type than the

spec

parameter (pants might be doing some magic, not sure)

I had another topic to close yesterday so I'm just working on this problem again. It "backfired" in the sens that target does not have a 'dependencies' field in its args:

Exception message: Invalid target mytarget: MyTarget received unknown arguments: 
  dependencies = ['the_spec']

In the Target class a comment on the constructor says

# NB: dependencies are in the pydoc above as a BUILD dictionary hack only; implementation hides
    # the dependencies via TargetAddressable.

But I have some pain finding out how TargetAddressable comes in play during the target building

OK - give me a minute to page this all back in...

yeah of course, thank you very much !

Injection is the right general concept but wrong tool. Only (v1) Tasks inject, Targets themselves use this: https://github.com/twitter/pants/blob/abc966fe12aa3ab545beb45600aeb788d8fadc0a/src/python/pants/build_graph/target.py#L628

\o/

SOrry for the twitter fork links 😕

no problem !