juniper-config-tools

Stdlib-only config helpers for the Juniper ML platform.

This package is the single source of truth for the env-var alias-with-deprecation helper that has been independently re-implemented across:

• juniper-cascor (CFG-03, CFG-05) — as pydantic @field_validators
• juniper-canopy (CFG-04, CFG-16) — as pydantic @field_validators
• juniper-cascor-worker (CFG-06, in flight) — as a standalone helper

The fourth repo's CFG-06 design surfaced the pattern as worth lifting. Cascor-worker's strict "no Pydantic at runtime" invariant (pinned by tests/test_no_pydantic_at_runtime.py, juniper-ml#168) ruled out juniper-observability (which requires pydantic>=2.0), so this package exists with a stdlib-only dependency policy.

This work mirrors the juniper-doc-tools PyPI migration plan (2026-05-18 doc-link validator incident) and the juniper-ci-tools PyPI migration plan (2026-05-20 dep-docs generator divergence).

The full design and rollout plan lives at notes/JUNIPER_CONFIG_TOOLS_PYPI_MIGRATION_PLAN_2026-05-22.md in the juniper-ml repo.

Installation

pip install juniper-config-tools

Runtime dependencies: none (stdlib only — os, warnings).

Quick start

from juniper_config_tools import env_with_legacy_alias

# Canonical name first; legacy alias triggers a DeprecationWarning when
# used.
server_url = env_with_legacy_alias(
    "JUNIPER_CASCOR_WORKER_SERVER_URL",  # new canonical name
    "CASCOR_SERVER_URL",                  # legacy alias (deprecated)
    default="",                           # returned if neither is set
)

Behaviour:

The DeprecationWarning text names both env-var names so operators can mechanically fix configuration. The warning is emitted with stacklevel=2 so the warning's reported location is the caller's, not this package's internals.

API

env_with_legacy_alias(new_name, legacy_name=None, default=None)

Returns str | None.

Why a separate package?

This package exists because juniper-cascor-worker cannot adopt juniper-observability (which requires pydantic) without breaking its load-bearing no-Pydantic-at-runtime invariant.

For consumers that already use pydantic-settings (juniper-cascor, juniper-canopy, juniper-data), this package is not a replacement — the pydantic field-validator pattern in their Settings classes is the right shape there. This package serves the constrained-runtime case.

Versioning

juniper-config-tools follows Semantic Versioning. Public API surface in 0.1.0 is a single function: env_with_legacy_alias. Consumers pin with juniper-config-tools>=0.1.0,<0.2.0 to opt out of future API growth that may add new functions without breaking changes.

License

MIT — see LICENSE.