Struct Engine 

pub struct Engine {
    pub resilient: bool,
    pub profile_override: Option<String>,
    pub budget: Budget,
    pub env: HashMap<String, String>,
    pub env_fallback: Option<EnvLookup>,
}

Fields

resilient: bool

profile_override: Option<String>

CLI --profile override: when set, selects this profile instead of the document’s active_profile key (spec §3.5).

budget: Budget

Runtime resource limits (spec/budgets.md, C-037). Violations are always fatal, in both modes.

env: HashMap<String, String>

The closed environment snapshot: the ONLY external input evaluation may read (spec/reproducibility.md §1, C-050). new() snapshots the process environment (CLI-compatible); with_env injects a fixed map (tests, agents, replays).

env_fallback: Option<EnvLookup>

Lazy host lookup consulted on snapshot miss, before defaults (F-016). None preserves legacy behavior exactly.

Implementations

impl Engine

pub fn new() -> Self

pub fn hermetic() -> Self

Hermetic engine: identical to new() except the environment starts empty instead of snapshotting the process ambient. Embeddings (FFI, WASM) use this so host ambient can never leak across the boundary; host values arrive only through explicit maps or lookup callbacks. Required on platforms without a process environment (wasm32-unknown-unknown aborts on ambient access): construct here, never snapshot-then-discard.

pub fn with_env(self, env: HashMap<String, String>) -> Self

Fixed environment snapshot instead of the process ambient.

pub fn with_env_fallback(self, lookup: EnvLookup) -> Self

Lazy host lookup consulted on snapshot miss (F-016).

pub fn evaluate( &self, module: &Module, ) -> Result<(Value, Vec<Diagnostic>), EvalError>

pub fn evaluate_incremental( &self, module: &Module, memo: &mut IncrementalMemo, ) -> Result<(Value, Vec<Diagnostic>), EvalError>

Incremental evaluation over a reused memo store (C-055, spec/performance.md §2): nodes whose structural fingerprint (expression shape, literal data, env values read, and dependency fingerprints) matches a previous call serve the memoized value and diagnostics; only the affected sub-DAG re-evaluates. Configuration changes (resilient flag, profile override, budgets) clear the store first. Post-walk transforms (profiles, patches, validation) re-run every call — they compose the final tree and stay cheap relative to the walk they follow.

Trait Implementations

impl Default for Engine

fn default() -> Self

Returns the “default value” for a type.