Struct Capabilities 

#[non_exhaustive]
pub struct Capabilities {
    pub reads_fs: bool,
    pub writes_fs: bool,
    pub network: bool,
    pub reads_clock: bool,
    pub reads_env: bool,
    pub uses_rng: bool,
    pub max_steps: Option<u64>,
    pub max_value_elements: Option<usize>,
}

Context-wide sandbox policy the host hands the evaluator. The per-bit booleans are the capabilities the host grants; per-function requirements live on NativeFnGate. A call goes through iff every bit declared on the fn’s gate is also set here — there is no per-name allowlist or global short-circuit, so a successful call proves that every bit on its gate was granted.

Beyond the capability bits, this struct also carries the runtime resource budgets (max_steps, max_value_elements) the evaluator enforces. The analyzer’s static reachability check only reads the capability bits and ignores the budgets, but they live on the same struct so the evaluator’s Context keeps a single sandbox-policy carrier (the budgets are Option<_> defaulting to “unbounded”, so a Capabilities built purely for the analyzer is unaffected).

#[non_exhaustive]: future capability bits are added here without a breaking semver bump. External callers should prefer constructing via Capabilities::default / Capabilities::all_granted and mutating fields rather than relying on field-order struct literals.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

reads_fs: bool

Filesystem reads (host fn that calls std::fs::read*, also the policy bit consulted by FilesystemModuleResolver).

writes_fs: bool

Filesystem writes (host fn that calls std::fs::write* / OpenOptions::write / create_dir* / remove_*).

network: bool

Network access (sockets, HTTP clients, DNS).

reads_clock: bool

Wall / monotonic clock reads (SystemTime::now, Instant::now).

reads_env: bool

Process environment reads (std::env::var, args, etc.).

uses_rng: bool

Random number generation (any non-deterministic source).

max_steps: Option<u64>

Maximum number of AST nodes to process before aborting. None is unbounded. Consulted only by the evaluator; the analyzer ignores it.

max_value_elements: Option<usize>

Maximum number of elements in a single List or Dict. None is unbounded. Consulted only by the evaluator; the analyzer ignores it.

Implementations

impl Capabilities

pub fn all_granted() -> Capabilities

Audit-visible “grant everything” preset: every capability bit flipped, no step / value-size budget. The spec forbids an implicit Context::trusted()-style shortcut; hosts that need full grant must call this and read the resulting Capabilities as data. See docs/zh/guide/spec.md §4.2.

Note: opening filesystem reads also requires installing a non-rejecting FilesystemModuleResolver. The reads_fs flag is the policy bit; the resolver is the machinery that enforces it.

Trait Implementations

impl CapabilityGate for Capabilities

Default gate implementation: consult the per-bit booleans on a Capabilities snapshot.

&Capabilities is the natural carrier on the tree-walker path — the Context already owns one. The cranelift backend constructs its CapabilityVtable from this gate as well, so the two paths share the exact same policy.

fn check(&self, cap: CapabilityBit) -> Result<(), CapabilityBit>

Return Ok(()) if the bit is granted; Err(cap) carrying the denied bit otherwise.

fn check_gate(&self, gate: &NativeFnGate) -> Result<(), CapabilityBit>

Check every bit set on gate, short-circuit on the first denial. Returns Ok(()) when the gate is fully satisfied — the canonical “may this native fn dispatch” question.

impl Clone for Capabilities

fn clone(&self) -> Capabilities

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Capabilities

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for Capabilities

fn default() -> Capabilities

Returns the “default value” for a type.