Re:What Is JSON Patch?
by masklinn on Tuesday May 10, 2022 @06:05AM
(#31325317)
> You can interpret a null field the same as a missing field.
Not in the general case no, they are two different states, which may have entirely different semantics.
For instance a missing field can mean "don't touch this field" while a field set to null means "set this field to null".
Some schemas might opt to ignore this distinction and collapse the states, but that is a specific decision, and an express loss of information.
> You only need to worry if you have arbitrary dictionary keys and need to differentiate a null value from an missing key.
There are other situations where that's an issue, like the above, or when you're using the object as a set (which JSON doesn't have), or when you've defined the schema to never have missing fields (but possibly have some set to `null`) so clients will break, ...
Not in the general case no, they are two different states, which may have entirely different semantics.
For instance a missing field can mean "don't touch this field" while a field set to null means "set this field to null".
Some schemas might opt to ignore this distinction and collapse the states, but that is a specific decision, and an express loss of information.
> You only need to worry if you have arbitrary dictionary keys and need to differentiate a null value from an missing key.
There are other situations where that's an issue, like the above, or when you're using the object as a set (which JSON doesn't have), or when you've defined the schema to never have missing fields (but possibly have some set to `null`) so clients will break, ...