How to reference relative to `$PREFIX` in `license_file`?

[mfansler]

In Conda Forge R recipes, we follow a standard practice of capturing a copy of the shared license file found in r-base. For example, in schema v0, if an R package has License: MIT + file LICENSE then we translate this to:

about:
  license: MIT
  license_family: MIT
  license_file: 
    - {{ environ["PREFIX"] }}/lib/R/share/licenses/MIT
    - LICENSE

where LICENSE is found in the source directory (included in original tarball).

Error Observed

We now have some recipes attempting to use the new v1 schema, but it is unclear how to translate the {{ environ["PREFIX"] }}. For example, on r-easy.utils PR, trying the translating according to https://github.com/prefix-dev/rattler-build/pull/260, we have

Syntax

- ${{ env.get("PREFIX") }}/lib/R/share/licenses/MIT

Result

2025-03-28T17:36:22.8752900Z Adding in variants from /opt/conda/conda_build_config.yaml
2025-03-28T17:36:22.8756439Z Adding in variants from /home/conda/staged-recipes-copy/.ci_support/linux64.yaml
2025-03-28T17:36:22.9167221Z 
2025-03-28T17:36:22.9170697Z  ╭─ Finding outputs from recipe
2025-03-28T17:36:22.9172446Z  │ Loading variant config file: "/tmp/tmp32hrtiq5"
2025-03-28T17:36:22.9277483Z  │
2025-03-28T17:36:22.9280300Z  ╰─────────────────── (took 0 seconds)
2025-03-28T17:36:22.9285709Z Error:   × Failed to parse recipe
2025-03-28T17:36:22.9288071Z 
2025-03-28T17:36:22.9288350Z Error: 
2025-03-28T17:36:22.9288772Z   × failed to render Jinja expression: invalid operation: Environment variable
2025-03-28T17:36:22.9289177Z   │ PREFIX not found (in <string>:1)
2025-03-28T17:36:22.9289578Z     ╭─[staged-recipes-copy/recipes/r-easy.utils/recipe.yaml:53:7]
2025-03-28T17:36:22.9289899Z  52 │   license_file:
2025-03-28T17:36:22.9290235Z  53 │     - ${{ env.get("PREFIX") }}/lib/R/share/licenses/MIT
2025-03-28T17:36:22.9290642Z     ·       ────────────────────────┬────────────────────────
2025-03-28T17:36:22.9291041Z     ·                               ╰── invalid operation: Environment variable PREFIX not found
2025-03-28T17:36:22.9291595Z  54 │     - LICENSE
2025-03-28T17:36:22.9291837Z     ╰────

Possibly Related

Maybe related to https://github.com/prefix-dev/rattler-build/issues/1439, which observed PREFIX as undefined.

[wolfv]

As a workaround, in the build, you could copy the files from the prefix to the work dir?

E.g

cp $PREFIX/licenses/foobar.* $SRC_DIR/licenses/

[mfansler]

Thanks for the quick reply. Yes, that can work. I.e., we could add to our boilerplate in bld.bat and build.sh to copy all the shared licenses. Not ideal, but doable.

I think the case we want to avoid is converting our now generic build scripts to something package specific.

Are there any plans to have PREFIX defined when the licenses are captured?

[wolfv]

I would say we don't have concrete plans right now. It would also not be super hard to do. We just have to decide that we want it, I guess.

[mfansler]

Just want to explicitly note that I would prefer this feature to copying in build scripts. Having a single expression that can handle shared license copying is cleaner than having coupled lines across multiple files.

[wolfv]

I think the main design question is whether we want:

license_file:
  source:
    - my_license.txt
  recipe_dir:
    - license.txt
  prefix:
    - license-foobar.txt

Or whether we go with

license_file:
  - ${{ RECIPE_DIR }}/foo/bar
  - ${{ PREFIX }}/foo/license.txt
  - ${{ SRC_DIR }}/foo/license.txt

Or if we continue doing what we are doing today, which is having a search order:

• first search SRC_DIR
• then search RECIPE_DIR
• and now we could add search $PREFIX

for the license file.

[baszalmstra]

How about:

license_file:
  - autodiscover.txt
  - prefix: from-prefix.txt
  - recipe-dir: from-recipe-dir.txt
  - source: from-source-dir.txt

[wolfv]

I guess I could live with this. In the tests section, we changed the schema a bit to use:

...
    files:
      source:
        - myfile.txt
        - tests/
        - some/directory/pattern*.sh
      recipe:
        - extra-file.txt
...

[mfansler]

Would multiple files from one context be

license_file:
  - prefix:
    -  from-prefix-1.txt
    -  from-prefix-2.txt

or

license_file:
  - prefix: from-prefix-1.txt
  - prefix: from-prefix-2.txt

?

---

Personally, I have a preference for the explicit requirement of context with:

license_file:
  source:
    - my_license.txt
  recipe:
    - license.txt
  prefix:
    - license-foobar.txt

Not a huge problem, but I do see newer users trip up on autodiscover of licenses. While autodiscovery is deterministic, it isn't self-evident from an example, whereas this is.

[baszalmstra]

It would indeed be:

license_file:
  - prefix: from-prefix-1.txt
  - prefix: from-prefix-2.txt

I think @wolfv s suggestion is also more in line with the rest of the recipe format so Id be happy to use that instead.

[beckermr]

Adding new keys to the schema is not something all tools will necessarily support without a CEP. I'm not a fan of schema extensions outside of the CEPs.

We should also standardize what env vars are available and what is available in the jinja.

Given everything else, I'd prefer the jinja route here. Constantly adding extra keys to the yaml to cover random additional locations / edge cases seems like an anti-pattern.

[mfansler]

Just adding ref to related PR: https://github.com/prefix-dev/rattler-build/pull/1648

[roaldarbol]

This seems to be blocking (are there more blocks?) towards adoption of v1 R recipes. The PR mentioned by @mfansler seems to tackle it, but has stalled - what would be needed to move forwards with this?

[wolfv]

I do want to pick this up again, but use ${{ PREFIX }} in the recipe file and then resolve that at "globbing time". Unfortunately that is a bit more involved...