Link to needs in dynamic functions

[Jattin]

Hi! I have a use case where i need to specify the requirements using a parameter.

.. par-dim:: Max length
    :id: DIM_1
    :value: 100
    :unit: m
    Definition:
       Max length that can be returned.

In the documentation, I want to use that parameter to state a requirement.
Expected:
The returned value should never exceed the length of 100 m.

So, I used the dynamic function to do that
The returned value should never exceed the length of [[get_param(id="DIM_1")]].

def get_param(app, need, needs, *args, **kwargs):
     param = needs[kwargs["id"]]
    return "{} {}".format(param["value"], param["unit"])

Now, if I want to link to the parameter, I have to change the code to
The returned value should never exceed the length of [[get_param(id="DIM_1")]] (see :need: DIM_1).

I wanted to ask whether this would be possible to return the link also in the dynamic function?
Basically, I want the dynamic function to return 100 m (see <link>).

[PhilipPartsch]

Hi,
I like your Idea, but I do not like to write such complex code in a rst file.
So I implemented a role for this job.
See Pull Request #468

[danwos]

I like the idea of @Jattin, but I'm not sure if it is easily technical possible.
Right now the return value of a dynamic function must be a string, which gets not interpreted as rst value.
So a returned **value** is printed as **value** and not as value.

But maybe to support the above use case, we do not need to use a dynamic function.

It's feels like a better :need: role could do it, if it has access to the need-values.
Right now you can use :need: in two ways:

1. :need:`DIM_1`
2. :need:`My own text <DIM_1>`

I would like to enhance the "string/naming-feature", to give it access to all the need values:
:need:`{{value}} {{unit}} of need {{id}} <DIM_1>`

Which would create a link with the text: 100 m of need DIM_1.

Would this be helpful?

[PhilipPartsch]

Why would you use {{ to provide a option?

[danwos]

Sphinx-Needs often use jinja for string templating, therefore the {{.
But it could be replaced with anything else.

[PhilipPartsch]

After a protoype in PR #611 we make following decisions:

• We want to go with [[ and ]] to indicate start and end of option to be fetched.
• We have to have a follow the python format handling, as it is how the parameter needs-role-need-template works
• As it is described in jinja2 format handling, it is better to use python build in format handling