CEP-0014: permit lists in context

[mgorny]

Description

Update the section describing the context block to permit lists of scalars in addition to scalars. Add a note that the resulting Jinja variable will have the same type as the value. For example, this can be used to declare lists of skipped tests, conveniently interspersing them with comments, and afterwards combining into a single string.

The change is backwards compatible and minimal, so it seems cleanest to update the specification in place rather than via another CEP.

See also: prefix-dev/rattler-build#1402

CC @wolfv

[mgorny]

@wolfv, well, it's been experimental for a while now. How do we proceed from here?

[wolfv]

I think it's time to call for a vote! :)

[wolfv]

Although I am unsure whether modifying existing CEPs in this way is "allowed". Let's ask on the conda CEP Zulip channel ...

[isuruf]

Does this mean we are allowed to do something like

context:
  build_reqs:
    - ${{ compiler('cxx') }}
    - make

recipe:
  name: test
  version: 0.1.0

outputs:
  - package:
      name: foo
    requirements:
      build: ${{ build_reqs }}

  - package:
      name: bar
    requirements:
      build: ${{ build_reqs }}

[wolfv]

I think this syntax would not work, but a list of list is flattened and that would then work, yes.

[mgorny]

Although I am unsure whether modifying existing CEPs in this way is "allowed". Let's ask on the conda CEP Zulip channel ...

I see the only reply was basically "yes", so should we (you?) start the vote?

[wolfv]

@mgorny we decided we can just "accept" this. Maybe you can take a look at my latest change to cep-0014 and add a little changelog thing as well? Then we can merge! Thank you & sorry for the long wait :)

[mgorny]

Rebased and added an entry.