Struct CarryContract 

pub struct CarryContract { /* private fields */ }

The carry a workloop threads from one generation to the next, and the DEFAULTS that seed generation 1 (R-carry).

🔴 WHY DEFAULTS ARE A CONTRACT AND NOT A CONVENIENCE

A workloop’s iteration body reads its carry fields unconditionally — the generated input codec requires them. Every generation after the first gets them from the previous iteration’s route start payload. Generation 1 has no previous iteration, so unless something seeds those fields the very first run of a loop fails to decode its own input: a start payload that passes schema admission and is then unreadable by the workflow it was admitted for.

Seeding is therefore the engine’s job at the START, not the author’s job at every call site — an operator starting a loop cannot be expected to know which fields the compiled codec will demand.

🔴 CALLER VALUES WIN

The merge is default-filling, never overwriting: a field the caller supplied keeps the caller’s value. A default that clobbered an explicit start value would make the declaration silently override the operator.

Implementations

impl CarryContract

pub fn none() -> Self

A loop that declares no carry: nothing to seed.

pub fn new(defaults: BTreeMap<String, Value>) -> Result<Self, WorkloopSpecError>

Builds a carry contract from declared field defaults.

Errors

Refuses an empty field name (WorkloopSpecError::EmptyCarryField).

pub const fn defaults(&self) -> &BTreeMap<String, Value>

The declared field defaults.

pub fn is_empty(&self) -> bool

Whether this loop declares any carry at all.

pub fn seed(&self, input: &Payload) -> Result<Payload, WorkloopSpecError>

Merge the declared defaults into a generation-1 start payload.

Returns the payload unchanged when nothing is declared. Caller-supplied fields are preserved; only ABSENT fields are filled.

Errors

Refuses a start payload that is not a JSON object (WorkloopSpecError::CarrySeedTargetNotAnObject) — there is nowhere to put a named field in a scalar or an array, and silently dropping the seed would reproduce the very decode failure seeding exists to prevent.

Trait Implementations

impl Clone for CarryContract

fn clone(&self) -> CarryContract

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CarryContract

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

Formats the value using the given formatter.

impl Default for CarryContract

fn default() -> CarryContract

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for CarryContract

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for CarryContract

impl PartialEq for CarryContract

fn eq(&self, other: &CarryContract) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for CarryContract

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for CarryContract