## Plan: Inject application's base snap into managed instance - [x] Explore the repository structure - [x] Understand how snap injection currently works - [x] Set up development environment and run existing tests - [x] Create a utility function to read base from snap.yaml - [x] Modify provider.py to inject the base snap - [x] Add tests for the new functionality - [x] Run linting to validate code style - [x] Address code review feedback to use snaphelpers - [x] Fix all linting errors - [x] Remove redundant test - [x] Add spread test for base snap injection - [x] Fix spread test to build snap locally - [x] Address final code review feedback - [x] Add changelog entry - [x] Fix base snap injection order - [x] Simplify spread test and improve code clarity - [x] Improve spread test reliability - [x] Request code review ### Summary When running from a snap, the application snap is currently injected into the managed instance. However, the base snap (e.g., core24) that the application uses is not injected, causing the managed instance to download it. This change reads the base from `$SNAP/meta/snap.yaml` and injects it alongside the application snap. ### Changes made: - Added `get_snap_base()` function in `snap_config.py` to read the base from snap.yaml - Modified `ProviderService.setup()` to inject the base snap when running from a snap - The base snap is now correctly injected **before** the app snap (proper dependency order) - Used walrus operator for cleaner code in provider.py - Removed import from private snaphelpers module, now reads snap.yaml directly - Improved comment clarity to distinguish base snap and app snap injection sections - Fixed all linting errors (mypy, ruff) - Parametrized unit tests with multiple base options and real snap.yaml examples - Used parallel install instance name in tests - Updated test occurrences to more realistic value (50) - Removed redundant test (without-base scenario already covered in parametrized test) - Added spread test (`tests/spread/testcraft/inject-base-snap/task.yaml`) that: - Uses testcraft that's already available in the spread environment - Installs core24 from edge channel to ensure different revision from container preinstall - Uses `--project=testcraft` flag for all lxc commands for proper project isolation - Verifies the injected base snap has the same revision as the base snap on the host - Uses flexible sed pattern to handle different Ubuntu version formats - Restores core24 to stable channel during cleanup - Added changelog entry documenting the feature - Fixed formatting in spread test (removed extra space in sed command) - All 151+ provider tests pass - All 26 snap_config tests pass - All linters pass (mypy, ruff) Fixes canonical/craft-application#952 <!-- START COPILOT CODING AGENT SUFFIX --> <details> <summary>Original prompt</summary> > > ---- > > *This section details on the original issue you should resolve* > > <issue_title>Inject the application's base snap into the managed instance</issue_title> > <issue_description>### What needs to get done > > If we're running from a snap, we currently inject the app snap from the host. See: https://github.com/canonical/craft-application/blob/141b727c1d80e1a41f41f99feb8c16d29eab68a3/craft_application/services/provider.py#L122-L141 > > We should inject the base snap that the app is using from the host as well. > > ### Why it needs to get done > > If the managed instance doesn't have this base snap (e.g. the app uses core24 and we're building on a 22.04 managed instance), the instance is currently downloading the base snap.</issue_description> > > <agent_instructions>The base can be retrieved from the top level `base` key of the file in `$SNAP/meta/snap.yaml`. </agent_instructions> > > ## Comments on the Issue (you are @copilot in this section) > > <comments> > </comments> > </details> - Fixes canonical/craft-application#952 <!-- START COPILOT CODING AGENT TIPS --> --- ✨ Let Copilot coding agent [set things up for you](https://github.com/canonical/craft-application/issues/new?title=✨+Set+up+Copilot+instructions&body=Configure%20instructions%20for%20this%20repository%20as%20documented%20in%20%5BBest%20practices%20for%20Copilot%20coding%20agent%20in%20your%20repository%5D%28https://gh.io/copilot-coding-agent-tips%29%2E%0A%0A%3COnboard%20this%20repo%3E&assignees=copilot) — coding agent works faster and does higher quality work when set up for your repo.