On 06/09/2012 01:16, Johan Tibell wrote:
Hi all,
The PVP says:
"A.B is known as the major version number, and C the minor version number. When a package is updated, the following rules govern how the version number must change relative to the previous version:
1. If any entity was removed, or the types of any entities or the definitions of datatypes or classes were changed, or instances were added or removed, then the new A.B must be greater than the previous A.B. Note that modifying imports or depending on a newer version of another package may cause extra instances to be exported and thus force a major version change."
The part about adding instances and the one about modifying imports makes it hard to follow the PVP. Bumping the major version number is a quite disruptive change for your users if they use upper bounds on their dependencies. Minor version bumps are not nearly as disruptive as you can you can depend on x.y.* as long as you only use qualified imports and/or explicit import lists.
Assuming no one uses orphan instances, adding instances is always safe because you can only add instances for types from packages you depend on, which means that they can't be depending on your package in turn and have defined a non-orphan instance for a type or class defined in your package.
I suggest that the rule be changed to not require a major version bump if instances are added.
Yes, I think this is reasonable. The client already has some obligations if they want to be independent of minor versions: they have to use explicit import lists. So adding another obligation, no orphan instances, is consistent with this and shouldn't cause problems in the majority of cases. Cheers, Simon
P.S. I believe the same reasoning can be applied to the import part of the rule above.
-- Johan
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