Context Keywords

Keywords for working with context variables and state.

Assignment

becomes

Sets a context value.

$total becomes 100
$status becomes "active"

is

Used in given: to set initial values.

given:
  $total: number is 100
  order is in #pending

Arithmetic Operations

increases by

Adds to a numeric value.

$total increases by 25
$retry_count increases by 1

decreases by

Subtracts from a numeric value.

$balance decreases by $amount
$stock decreases by $quantity

Collection Operations

adds

Adds an item to a collection.

$items adds "Laptop"
$tags adds "priority"

removes

Removes an item from a collection.

$items removes "Mouse"
$tags removes "draft"

clears

Empties a collection.

$items clears
$cart clears

State Keywords

State Transition Verbs

All equivalent:

• moves to
• transitions to
• enters
• becomes
• changes to

order moves to #paid
order transitions to #approved
payment enters #processing
ticket becomes #closed

is in / is not in

Checks current state.

? order is in #pending
  process order

? order is not in #cancelled
  allow modification

Context Validation

Post-Action Validation Table

Defines constraints for context variables after actions. The table follows the action(s).

Single variable:

$retry_count increases by 1
  | $retry_count | required, integer, between 0 and 5 |

Multiple variables:

$total increases by $item.price
$item_count increases by 1
  | $total      | required, number, greater than 0 |
  | $item_count | required, integer                |

Validation Rules

Rules are comma-separated. Common rules:

Rule	Description
required	Must be present and not null
optional	May be absent
string, number, integer, boolean, array, object	Type rules
greater than N, less than N, between N and M	Numeric rules
at least N, at most N	Numeric bounds
min N characters, max N characters	String length
valid email, valid uuid, valid url	Format rules
one of "a", "b"	Enum rule
bail	Stop on first error

See Data Validation for complete rule reference.

Constraint Violation

When a constraint is violated:

1. The action is rolled back (value unchanged)
2. :constraint_violated event is emitted

on :constraint_violated
  ? $field is "$retry_count"
    emit :max_retries_exceeded to @customer