pika-orch-incus-cleanup-23

The core of the refactor lives in model.rs. Three new structs capture backend-specific knobs:

pub struct HostProcessRuntimeConfig;

pub struct IncusRuntimeConfig {
    pub staged_linux_command: Option<StagedLinuxCommandConfig>,
}

pub struct TartRuntimeConfig {
    pub host_setup_command: Option<&'static str>,
    pub mount_host_rust_toolchain: bool,
}

These are unified under a single enum:

pub enum JobRuntimeConfig {
    HostProcess(HostProcessRuntimeConfig),
    Incus(IncusRuntimeConfig),
    Tart(TartRuntimeConfig),
}

JobSpec loses its three flat fields (staged_linux_command, host_setup_command, mount_host_rust_toolchain) and gains a single runtime_config: JobRuntimeConfig field.

The existing accessor methods (staged_linux_command(), host_setup_command(), mount_host_rust_toolchain()) are preserved for backward compatibility at the call-site level, but now dispatch through match on the runtime config enum. The runtime_kind() method switches from reading self.execution.runtime to deriving the kind from self.runtime_config().kind(), and a debug_assert_eq! in runtime_config() cross-checks that the execution config and runtime config agree—catching misconstruction during development without runtime cost in release builds.

lib.rs adds the four new types to its pub use model::{...} block:

• HostProcessRuntimeConfig
• IncusRuntimeConfig
• JobRuntimeConfig
• TartRuntimeConfig

The StagedLinuxCommandConfig type was already re-exported. The diff simply extends the existing pub use statement with the new symbols, keeping alphabetical order.

Two helper functions are introduced at the top of main.rs:

fn remote_incus_runtime(
    staged_linux_command: Option<StagedLinuxCommandConfig>,
) -> JobRuntimeConfig {
    JobRuntimeConfig::Incus(IncusRuntimeConfig {
        staged_linux_command,
    })
}

fn tart_runtime(mount_host_rust_toolchain: bool) -> JobRuntimeConfig {
    JobRuntimeConfig::Tart(TartRuntimeConfig {
        host_setup_command: Some(TART_HOST_SETUP_COMMAND),
        mount_host_rust_toolchain,
    })
}

The three base job constructors (remote_incus_job_base, host_local_job_base, tart_job_base) each replace the three flat fields with a single runtime_config field.

Every individual job spec construction throughout main.rs follows the same mechanical pattern:

• Incus jobs with a staged command: staged_linux_command: Some(...) becomes runtime_config: remote_incus_runtime(Some(...)).
• Incus jobs without a staged command: The field is removed entirely (inherited from ..remote_incus_job_base()).
• Host-local jobs: staged_linux_command: None is removed (inherited from ..host_local_job_base()), or explicitly set to JobRuntimeConfig::HostProcess(HostProcessRuntimeConfig) when overriding the base.
• Tart jobs: mount_host_rust_toolchain and staged_linux_command: None are replaced with runtime_config: tart_runtime(true/false).

The build_snapshot_mount_plan_for_test function in executor/incus.rs constructs a JobSpec directly. The three flat fields are replaced with:

runtime_config: super::super::JobRuntimeConfig::Incus(
    super::super::IncusRuntimeConfig {
        staged_linux_command: None,
    },
),

The host_setup_command: None and mount_host_rust_toolchain: false lines are removed since they are no longer part of JobSpec.

The test module in executor.rs receives the same treatment:

1. New imports: HostProcessRuntimeConfig, IncusRuntimeConfig, JobRuntimeConfig.
2. A local remote_incus_runtime() helper mirrors the one in main.rs.
3. remote_incus_job_base() and host_local_job_base() replace flat fields with runtime_config.
4. Every test that previously set staged_linux_command: None as an override now simply omits it, relying on the base constructor's default runtime_config.

The model.rs test module follows the identical migration pattern:

• A local remote_incus_runtime() helper is added.
• remote_incus_job_base() and host_local_job_base() use runtime_config instead of the three flat fields.
• Tests constructing jobs with staged_linux_command: Some(...) now wrap the value in remote_incus_runtime(Some(...)).
• Tests that set staged_linux_command: None as an override simply drop the line, inheriting from the base.

The run.rs test module is the largest consumer of JobSpec in tests. The migration is mechanical and consistent with the other modules:

• New imports for HostProcessRuntimeConfig, IncusRuntimeConfig, JobRuntimeConfig.
• A local remote_incus_runtime() helper.
• Updated remote_incus_job_base() and host_local_job_base() constructors.
• All individual test specs migrated from flat fields to runtime_config.
• Redundant staged_linux_command: None overrides removed.

A new invariant is appended to invariants/invariants.toml:

[[invariant]]
id = "PIKACI-005"
area = "pikaci"
kind = "must"
statement = "Backend-specific setup lives in explicit runtime config data, not ad hoc top-level JobSpec fields."
scope = ["crates/pikaci/**"]
hint = "Focus on the JobSpec data model and how main.rs builds jobs. Fail if production JobSpec still has loose top-level fields like staged_linux_command, host_setup_command, or mount_host_rust_toolchain."

This invariant complements the existing PIKACI-004 (which forbids runtime dispatch based on naming conventions) by ensuring the data model itself groups backend knobs under the correct variant. Together they enforce that both the data shape and the dispatch logic are explicit and type-safe.