Struct MapMapping 

pub struct MapMapping {
    pub path: PathTemplate<ContextRoot>,
    pub logic: Value,
    pub unset: bool,
    pub on_null: OnNull,
    /* private fields */
}

A single mapping that transforms and assigns data — or, with unset, removes it.

Three rules hold between the keys, and a definition breaking one fails to parse (so Workflow::validate_authored reports it as IssueCode::InvalidMapping and Engine::build refuses it):

• a mapping has logic or "unset": true, never both;
• on_null needs logic, since it says what a null result does;
• a removal may not name a context root (data, metadata, temp_data). A literal path is checked here; a computed one that resolves to a root fails that mapping at run time instead.

Fields

path: PathTemplate<ContextRoot>

Target path where the result will be stored (e.g., "data.user.name"). Supports dot notation for nested paths and # prefix for numeric field names.

JSONLogic, so a mapping can compute where it writes: {"cat": ["data.accounts.", {"var": "data.id"}, ".balance"]}. The static spelling is a literal string, which folds at compile time and keeps the precomputed split this hot loop has always used — a dynamic path is the only one that pays to split per write.

logic: Value

JSONLogic expression (kept as serde_json::Value since this is the shape the compiler accepts; not runtime data).

Value::Null on an unset mapping, which has none.

unset: bool

Remove the key at path instead of writing to it. Takes no logic.

A no-op when the key is already absent. A removal is recorded on the audit trail as a Change with removed set.

This exists because null cannot mean “clear”: a null result is skipped (see OnNull::Skip), which is what lets {"if": [cond, value, null]} mean “set or keep”.

on_null: OnNull

What a null result from logic does. Defaults to OnNull::Skip, the historical behaviour.

Trait Implementations

impl Clone for MapMapping

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MapMapping

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

Formats the value using the given formatter.

impl Default for MapMapping

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for MapMapping

fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error>

Deserialize this value from the given Serde deserializer.