fix(setup-python-runner): honour use-lxd input to skip LXD installation

[lengau]

use-lxd: false had no effect: setup-python-runner never declared a use-lxd input (its "Setup LXD" step only checked runner.os == 'Linux'), and test-python.yaml never passed its use-lxd input through to the action.

Adds the input to the action, gates the LXD setup step on it, wires it through from test-python.yaml, and defaults it to true everywhere to preserve current behaviour. Adds regression self-tests.

[Copilot]

Pull request overview

This PR fixes the setup-python-runner composite action and related workflows so the use-lxd input actually controls whether LXD is installed on Linux runners, and adds regression coverage to prevent reintroducing the issue.

Changes:

• Add use-lxd input to setup-python-runner and gate the “Setup LXD” step on it.
• Wire use-lxd through .github/workflows/test-python.yaml and default it to true to preserve current behavior.
• Add self-test/regression workflows validating both the disabled path and step-level outcomes.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
setup-python-runner/action.yaml	Introduces use-lxd input and conditions the LXD setup step on it.
.github/workflows/test-python.yaml	Defaults use-lxd to true and passes it through to the setup action across jobs.
.github/workflows/self-test-setup.yaml	Adds a self-test job validating use-lxd: false avoids installing LXD.
.github/workflows/self-test-qa.yaml	Adds a regression run plus verification logic to confirm the “Setup LXD” step outcome differs when toggling use-lxd.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (2)

setup-python-runner/action.yaml:29

• use-lxd is declared as a boolean input, but the step condition parses it with fromJSON(...). If the action runtime provides typed boolean inputs, fromJSON can fail due to a type mismatch; if it provides strings, fromJSON is unnecessary complexity. Prefer a condition that works for both boolean and string representations without JSON parsing.

    - name: Setup LXD
      if: ${{ runner.os == 'Linux' && fromJSON(inputs.use-lxd) }}
      uses: canonical/setup-lxd@v1

.github/workflows/self-test-setup.yaml:122

• This self-test assumes /snap/bin/lxc is absent on the runner when use-lxd: false. If the runner image ever ships with LXD/LXC preinstalled, the test will fail even though the action correctly skipped installation. Capture the pre-state and only fail when the action introduces /snap/bin/lxc on a previously-clean runner.

      - uses: ./setup-python-runner
        with:
          use-lxd: false
      - name: Check lxd is not installed
        run: |
          if [ -e /snap/bin/lxc ]; then
            echo "::error::/snap/bin/lxc should not exist when use-lxd is false"
            exit 1
          fi

[lengau]

Focal LXD 6 failure is external, handled with: canonical/setup-lxd#41