extend docs

[DerThorsten]

There is now docs at https://emscripten-forge.org with very little content, lets add:

• use packages with lite / xeus-python
• debug local builds: This should describe how to use the rattler-build way of debugging.
• credit section
• todo section
• blog / news section
• global pinning / conda-build-config
• maintainers section:
  • overview of ci itself
  • uploading packages via ci
  • building/extending the documentation
  • bots
• hints how to add packages:
  • header only c++
  • static library c++
  • shared library c++
  • python with:
    • pybind11
    • libffi
    • meson
    • rust (extended docs #935 )

[anutosh491]

As we have quite some "r-XX" packages now, we should document how one can add more.

[rgaiacs]

During a conversation on Zulip, I noticed that the documentation for R packages is missing. Any shared notes for R-packages that I could use? Thanks!

[IsabelParedes]

Hi @rgaiacs !

For R packages, here is a basic template example

context:
  version: 2.1.6
  name: r-readr

package:
  name: ${{ name }}
  version: ${{ version }}

source:
  url:
  - https://cran.r-project.org/src/contrib/${{ name[2:] }}_${{ version }}.tar.gz
  - https://cloud.r-project.org/src/contrib/${{ name[2:] }}_${{ version }}.tar.gz
  sha256: 9d743ba3b0453448ae5dea0582d5d7e5a2ef0489308d04cff7672865540546d9

build:
  number: 0
  script: $R CMD INSTALL $R_ARGS .

requirements:
  build:
  - cross-r-base_${{ target_platform }}
  - ${{ compiler('c') }}
  - ${{ compiler('cxx') }}
  - r-pkg01
  - r-pkg02
  host:
  - r-pkg01
  - r-pkg02
  run:
  - r-pkg01
  - r-pkg02

tests:
- package_contents:
    lib:
    - R/library/${{ name[2:] }}/libs/${{ name[2:] }}.so

The important bits:

• There needs to be 2 urls because very frequently the first one is not reachable
• The build script is almost always the same unless the package requires some special patching
• For the build requirements, cross-r-base is the most important package. This sets the dependency on r-base, so r-base does not need to be added or pinned in the recipe.
• All other R-dependencies need to be in all 3 sections (build, host, and run). They need to be in build and host so that cross-r-base can properly set the cross-compilation. And they also need to be in run because they should be run dependencies 😅
• For the tests, we only check that the shared library for the package exists. Eventually we should be able to load the package and do actual tests, but that's not available yet.

Hope this helps!

[rgaiacs]

Thanks for the template for the R package.