renderable_example1.py

# renderables ('Agreation' solution)

@any_kind_of_decorator_to_declare_a_renderable_pre_init
def commandRenderable1(prop):
    # A renderable cannot access to the self of a step, since it is evaluated before the actual initialization. So it cannot change the "self" state, and cannot add step logs
    ...
    a = prop.getProperty('aproperty')
    ...
    return the_actual_commands_to_add

@any_kind_of_decorator_to_declare_a_renderable_post_init
def commandRenderable2(self):
    # This renderable can access to the self of a step, since it is evaluated **after**initialization. 
    # So it can change the "self" state, and cannot add step logs
    ...
    a = self.getProperty('aproperty')
    self.addLogStdio("blablabla")
    ...
    return the_actual_commands_to_add

@any_kind_of_decorator_to_declare_a_renderable_post_execution  # is it really needed ?
def postExecute(self, res):
    # This renderable can access to the self of a step and access to every member it needs to to do its job
    # it is evaluated AFTER the step execution.
    # So it can change the "self" state (modification is useless), and can add step logs, upload files to location,...
    ...
    if res == FAILURE and some_reason:
       res = WARNINGS
    return res


steps.append(BuildStep(command=commandRenderable[1/2/3], 
                     postExecute=postExecute))

# 'Inheritance' Solution

class TheSpecialBuildStep(BuildStep):
    def command(self):
        # not the same signature than the renderable, but same name.
        # it has the self so can change the state of the step directly even if it is not advises.
        # it can add logs
        ...
        a = self.getProperty('aproperty')
        self.addLogStdio("I can describe what I will do since I have self").
        self.some_variable = some_value
        ...
        return the_actual_commands_to_add

    def postExecute(self, res):
       if res == FAILURE and some_reason:
           res = WARNINGS
       return res

steps.append(TheSpecialBuildStep)