git.stella-ops.org/docs/workflow/tutorials/08-expressions/README.md

Tutorial 8: Expressions

The expression system enables declarative logic that compiles to portable canonical JSON. All expressions are evaluable at runtime without recompilation.

Path Navigation

Prefix	Source	Example
start.*	Start request fields	start.policyId
state.*	Mutable workflow state	state.customerName
payload.*	Task completion payload	payload.answer
result.*	Step result (by resultKey)	result.productInfo.lob

Built-in Functions

Function	Description	Example
coalesce	First non-null	coalesce(state.id, start.id, 0)
concat	String join	concat("Policy #", state.policyNo)
add	Sum	add(state.attempt, 1)
if	Conditional	if(state.isVip, "VIP", "Standard")
isNullOrWhiteSpace	Null/empty check	isNullOrWhiteSpace(state.name)
length	String/array length	length(state.items)
upper	Uppercase	upper(state.annexType)
first	First array element	first(state.objects)
mergeObjects	Deep merge	mergeObjects(state, payload)

Variants

• C# Expression Builder
• JSON Expression Format

Next

Tutorial 9: Testing — unit test setup with recording transports.