json/yaml/toml functions

[begoon]

I have a complete PR (begoon#1) ready with tests.

Alas, I cannot raise it to upstream (@casey), so I will write in the discussions if there is interest in this functionality.

Structured Data

• json(filename, key1, key2, ...) - Read a JSON file and index into it with
  the given keys. For mappings, keys are used as field names. For arrays, keys
  are parsed as integer indices. Returns the final scalar value as a string.
  Aborts if the file is missing, the content cannot be parsed, a key is missing,
  an array index is invalid, or the final value is not a scalar.

  version := json('package.json', 'version')

• toml(filename, key1, key2, ...) - Read a TOML file and index into it, using
  the same rules as json().

  version := toml('pyproject.toml', 'project', 'version')

• yaml(filename, key1, key2, ...) - Read a YAML file and index into it, using
  the same rules as json().

  rustflags := yaml('.github/workflows/ci.yaml', 'env', 'RUSTFLAGS')

[casey]

I see the utility, but jq is ubiquitous and much more comprehensive. I think if we added something like json() it would be a long tail of feature requests, and users would probably be better off using jq.

[begoon]

What about toml and yaml?

I personally have this version.py in almost every Python project to query the version in CI.

import tomllib
from pathlib import Path
from typing import Final

info: Final = tomllib.loads(
    (Path(__file__).parents[1] / "pyproject.toml").read_text()
)

VERSION: str = info["project"]["version"]
DESCRIPTION: str = info["project"]["description"]

if __name__ == "__main__":
    print(VERSION)

[casey]

I agree it's useful. TOML and YAML are quite large, and by exposing toml() and yaml(), we would be making whichever TOML and YAML parsers we used part of just's interface, which always makes me nervous.

[bluefing]

There is yq for yaml - I'm using it to process the just dump.

https://github.com/mikefarah/yq

Apparently yq also has TOML support although i haven't used it for that. https://mikefarah.gitbook.io/yq/v/v4.x/usage/toml

It has a similar syntax to jq

# Dump the full just module tree as YAML (for bootstrapping spec.yaml)
[group('test')]
[script]
dump: _require-yq _full-render
    just -f "{{ _full_render }}/Justfile" --dump --dump-format json | yq -P