(feat request) Add a gazelle directive for using requirement() for pip-installable dependencies

[dougthor42]

🚀 feature request

Relevant Rules

• gazelle
• requirements.bzl

Description

Gazelle generates deps using the library labels directly, rather than using requirement() (possibly because of the drawbacks of requirement()).

# using labels
py_library(
    name = "foo",
    srcs = ["foo.py"],
    deps = ["@pip_parse_name//boto3"],
)

# using `requirement()` function
load("@pip_parse_name//:requirements.bzl", "requirement")

py_library(
    name = "foo",
    srcs = ["foo.py"],
    deps = [requirement("boto3")],
)

It would be great if we could configure this on a per-package basis. Users would then be able to opt-in to using requirement(), making the transition from manually-built BUILD files to gazelle-generated files much easier (as the diff will be much smaller or nonexistent¹).

Describe the solution you'd like

Add a new directive gazelle:python_use_pip_requirement_function (or similar name) that accepts 3 values:

• false (the default): Use library labels directly. Same as current behavior.
• true: Use requirement("library")
• DEFAULT or RESET: reset to the default as defined by rules_python.

Example:

# no directive set. Use labels directly.
py_library(
    ...,
    deps = ["@pip_parse_name//boto3"],
)

# gazelle:python_use_pip_requirement_function false
py_library(
    ...,
    deps = ["@pip_parse_name//boto3"],
)

# gazelle:python_use_pip_requirement_function true
load("@pip_parse_name//:requirements.bzl", "requirement")
py_library(
    ...,
    deps = [requirement("boto3")],
)

# gazelle:python_use_pip_requirement_function DEFAULT
py_library(
    ...,
    deps = ["@pip_parse_name//boto3"],
)

Describe alternatives you've considered

None 🙃. I'm happy to hear some though.

Footnotes

1. The docs guide users to use requirement() initially, and I'm not sure how many people opt to use labels instead. ↩

[aignas]

For now the workaround would be for users to first migrate to the string labels, which should be doable with sed, unless there is more to the problem at hand?

[dougthor42]

No I don't think there's any issue with doing a one-time sed to switch to the string labels.

It looks like this request is larger than I anticipated and might require an update to the bazel core (see bazel-contrib/bazel-gazelle#1747).

It's not a high priority. I just figured that (a) the docs seem to recommend requirement("foo") and (b) using such would make renaming the pip.parse hub_name have a lot smaller impact, diff-wise (though such a rename is probably very rare).

[aignas]

Yeah, I think we could change docs to show preference towards macroless dependency labels. I'll ask on Slack for what people prefer might be a good idea before changing the docs.

[github-actions]

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