method.output_multiplicity_mismatch

A pipe's declared multiplicity does not fit its use


Type	`https://mthds.ai/errors/method.output_multiplicity_mismatch`
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 pipe's declared output multiplicity does not fit how the method uses it. Validation finds it before any run; its run-time twin is pipe.output_multiplicity.

What to do

Make the output one item, a list, or a list of a fixed length, as its consumer expects, or change the consumer.

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`	Declare the output of pipe '`{pipe}`' with the multiplicity '`{expected}`', or change its use, then validate the method again.
Any other reader	`contact_owner`	Ask the method's owner to fix the output multiplicity of pipe '`{pipe}`'.

Detail

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

Pipe '{pipe}' declares its output with the multiplicity '{declared}', but its use expects '{expected}'.

Parameters

Every parameter is present on every occurrence of the code.

Name	Type	Description
`pipe`	`identifier`	The pipe at fault.
`declared`	`identifier`	The multiplicity the pipe declares.
`expected`	one of `single`, `list`, `fixed`	The multiplicity its use expects: one item, a list, or a list of a fixed length.