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Add some clarifications to revised default value design doc

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Jaykumar Gosar 2022-09-19 12:05:18 -07:00 committed by Jaykumar Gosar
parent 2a97421ab9
commit ee0b4ff90d
1 changed files with 13 additions and 9 deletions
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designs/defaults-and-model-evolution.md
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@ -320,16 +320,20 @@ The following shapes have restrictions on their default values:
### Updating default values
The default value of a member MAY be changed. The default value of a root-level
shape MUST NOT be changed since that would break any shape that refers to
the shape, and could break other models that refer to a shape defined in a
shared model.
The default value of a root-level shape MUST NOT be changed since that would
break any shape that refers to the shape, and could break other models that
refer to a shape defined in a shared model.
The default value of a member SHOULD NOT be changed. However, it MAY be
necessary in extreme cases to change a default value if changing the default
value addresses a customer-impacting issue or availability issue for a service.
Changing default values can result in parties disagreeing on the default value
of a member because they are using different versions of the same model.
The default value of a member that targets a shape with a default value
MUST NOT be removed (by changing the value to `null`) since that would
transition the member from non-optional to optional in generated code.
The default value of a member that targets a shape without a default value
SHOULD NOT be changed. However, it MAY be necessary in extreme cases to change
a default value if changing the default value addresses a customer-impacting
issue or availability issue for a service. Changing default values can result
in parties disagreeing on the default value of a member because they are using
different versions of the same model.
### Readers MUST NOT differentiate from omitted or defaulted