Guardrails / python

Build backend is declared

python/build-backend-declared@v1

A packaged project names its build backend in [build-system], so it builds the same way everywhere.

Id	python/build-backend-declared
Version	v1
Category	python
Default severity	warning
Interpreter	python3
Timeout	30 seconds
Violations tolerated	0
Collects	python

Collectors

This guardrail gathers nothing itself. It depends on the collectors below, which the CLI runs once per build before any check, and reads what they found out of GUARDRAIL_FACTS. A collector that collects nothing skips this guardrail rather than failing it.

Collector	Gathers	Inputs it is given
python	The Python project in the project directory: its manifest and build backend, the Python version it asks for, the requirements it declares and which of them are pinned, and the lock files committed beside them.	projectDir

The inputs above are this guardrail's own, passed straight through. Configuring one in buildnote.json changes what is collected, and two guardrails configured the same way share the one collection.

Configuration

{
  "guardrails": {
      "failOn": "error",
      "comment": true,
      "checks": [
          {
              "use": "python/build-backend-declared@v1",
              "severity": "warning",
              "with": {
                  "projectDir": "."
              },
              "exemptions": []
          }
      ]
  }
}

Inputs

Input	Description	Default	Environment variable
projectDir	Directory holding the project, relative to the directory the CLI runs in.	.	GUARDRAIL_INPUT_PROJECTDIR

How to fix

Declare the backend in pyproject.toml:

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

With no [build-system] table, PEP 517 falls back to legacy setuptools with whatever version the environment has, so the wheel a release builds depends on the machine that built it.

More in python

• python/lockfile-committed. The project commits a lock file, so an install of the same commit resolves the same versions.
• python/single-lockfile. The project commits at most one lock file, so two installers do not each believe they own the environment.
• python/version-declared. The project declares the Python version it is built and run against, and that version is no older than the configured floor.

All 4 python guardrails