method.optional_unhandled

An optional value reaches a place that needs a required one


Type	`https://mthds.ai/errors/method.optional_unhandled`
Family	`method`: The method as written, the validation vocabulary included.
Domain	`method`: the method's author acts, by changing the method
Retry	`no`: repeating the operation fails the same way
HTTP status	`422`
Raised as	a problem document, sent as the body of an HTTP response or kept in a run's record

What it means

A maybe-absent input or output is used where a value is required: it escapes through a step, a sequence or a condition whose boundary is not optional, a PipeCondition can continue without producing its output while that output is not ?, a template reads it without a guard, or a maybe-absent PipeParallel branch feeds a required structured field.

What to do

Guard the read, declare the receiving output or field optional with ?, or force the input with ! when it is always present at that point.

Next steps

A problem carries the step aimed at whoever reads it: the first when its reader is the domain's actor, the method's author, and the second for any other reader.

Reader	Kind	Detail
The domain's actor	`change_method`	Guard '`{input}`' where it is used, or declare the receiving side optional, then validate the method again.
Any other reader	`contact_owner`	Ask the method's owner to guard the optional '`{input}`' in pipe '`{pipe}`'.

Detail

The problem's detail is written from this template, filled with the occurrence's parameters:

In pipe '{pipe}', the maybe-absent '{input}' reaches a place that needs a value (site: {site}).

Parameters

Every parameter is present on every occurrence of the code.

Name	Type	Description
`pipe`	`identifier`	The pipe at fault.
`input`	`identifier`	The maybe-absent input or output.
`site`	one of `sequence_step`, `condition`, `condition_output`, `template`, `parallel_branch`	Where the value escapes: `sequence_step` when it escapes through a step or a sequence whose boundary is not optional, `condition` when it escapes through a condition whose boundary is not optional, `condition_output` when a `PipeCondition` can continue without producing its output while that output is not `?`, `template` when a template reads it without a guard, and `parallel_branch` when a maybe-absent PipeParallel branch feeds a required structured field.