Following the SemVer guidelines with x.y.z, I know I should start my developments with version 0.1.0 and do the following in case of:
Breaking change: increment y instead of x (which shall remain to 0 until the first production release).
Feature: ???
Patch: increment z.
As the question marks suggest, should I increment y or z when adding a new feature to my unreleased app?
The SemVer specification gives these instructions:
Patch version Z (x.y.Z | x > 0) MUST be incremented if only backwards compatible bug fixes are introduced. [...]
Minor version Y (x.Y.z | x > 0) MUST be incremented if new, backwards compatible functionality is introduced to the public API. [...]
Major version X (X.y.z | X > 0) MUST be incremented if any backwards incompatible changes are introduced to the public API. [...]
So basically, Z is incremented for fixes, Y is incremented for features, X is incremented for breaking changes whether they're about features or fixes.
While in the initial developments phase, we just don't deal with the breaking change part because we have no production users. Therefore, we should increment Z for fixes, and Y for features,
no matter if the changes are backwards compatible or not.
Related
Say I have written a piece of software (in R, for didactic purposes) which is following the Semantic Versioning Specification. This is the content of version 1.0.0 of the software:
funk <- function(x) {
jitter(x)
}
Which works so that
set.seed(1)
print(funk(0))
yields
[1] -0.009379653
Now suppose I change my function to this:
funk <- function(x) {
unrelated_random_stuff <- sample(1:10)
jitter(x)
}
And now, set.seed(1); print(funk(0)) yields
[1] -0.01176102
According to SemVer, does this constitute a major change? I.e., if I publish the software with these changes, should it be 2.0.0? I'm inclined to think so, since this technically changes results from scripts based on version 1.0.0, but I am not sure this qualifies as "breaking backwards compatibility" since we're talking about randomly-generated numbers.
If your customers are inclined to take a dependency on the output value, then yes, you probably want to bump the major version number. Even if this is library code, it's possible someone is using it for fuzz testing and it's critically important to yield reproducible result, in order to find track down and fix bugs, as well as ensure the fix does not regress in the future.
This question already has answers here:
Can I force the use of my dependencies' Cargo.lock when resolving package versions?
(1 answer)
How do I pin indirect dependencies of a crate?
(2 answers)
Closed 2 years ago.
I have two crates X and Z and I want to use both but X depends on Z of on some specific version. For example, mongodb depends on tokio 0.2 and I was using tokio 0.3.
X does not re-export Z so I (think) have to manually specify Z in Cargo.toml. If I specify the wrong version, it might break. How can I tell cargo to use whatever version of Z that X requires?
Cargo has some automatic dependency version resolution capability. You should be able to specify whatever version requirements of Z you need, and cargo will figure out how to choose the correct version to (potentially) use in both your code and X.
This is assuming both crates correctly use semantic versioning.
If X doesn't expose Z in any way, you don't really need to use the same version of Z. If you use a different major version of Z than X, Cargo will just use both versions of Z, once for you and once for X.
See alexcrichton's comments on this for a little bit more detail.
Currently, I use the semantic versioning for an API.
Versioning is envolves like this:
MAJOR version when you make incompatible API changes
MINOR version when you add functionality in a backwards compatible manner
PATCH version when you make backwards compatible bug fixes
Should I increment the PATCH, if I only update the documentation (swagger, internal documenation, YAML, ...) to add example, or correct a description attach to the API?
Thanks for your help ;)
Should I increment the PATCH, if I only update the documentation (swagger, internal documenation, YAML, ...) to add example, or correct a description attach to the API?
Depends on the example/correction. Does it represent a break from previous understanding of the use of your API's? Here's a very contrived example for discussion:
API: int plus(int a, int b)
Documentation: int plus(int a, int b) sums a + b.
The above was released as 1.0.0, then someone reviews the code and points out that on overflow, the function returns 0.
Updated documentation: int plus(int a, int b) sums a + b where a < 32767 and b < 32767, otherwise, returns 0.
So, whether this is a breaking change, depends on the language and its behavior when a + b overflow. Some languages throw an exception or segfault, others, it's common for them to simply return a modulo result of some kind. Let's say it's C, in that case, this documentation change is likely a breaking change (well, probably most programming languages actually).
The point here is that initial documentation is often not much better than a superficial restatement of the API itself. Subsequent complaints (bug reports) from customers, often drive the next round of documentation changes, when the customers are surprised by the results. So yes, even though the original intent of the developer hasn't changed, the documentation does represent a breaking change in regard to the expected results.
Had the documentation been changed to match exactly what the customers expected/witnessed in use, then no, it's not a breaking change.
The documentation is part of the feature set. Back-filling missing documentation is usually a feature addition, so you'd bump the minor version. A minor correction would be a patch.
When releasing a library on Hackage, how can I determine reasonable bounds for my dependencies?
It's a very brief question - not sure what additional information I can provide.
It would also be helpful to know if this is handled differently depending on whether stack or cabal is used.
Essentially my question relates to the cabal constraints which currently is set as:
library
hs-source-dirs: src
default-language: Haskell2010
exposed-modules: Data.ByteUnits
build-depends: base >=4.9 && <4.10
, safe == 0.3.15
I don't think the == is a good idea.
This is a tricky question, since there are different opinions in the community on best practices, and there are trade-offs between ease of figuring out bounds and providing the most compatibility with versions of dependencies possible. As I see it, there are basically three approaches you can take:
Look at the version of the dependencies you're currently using, e.g. safe-0.3.15. Assume that the package is following the PVP and will not release a breaking change before version 0.4, and add this: safe >= 0.3.15 && < 0.4
The above is nice, but limits a lot of potentially valid build plans. You can spend time testing against other versions of the dependency. For example, if you test against about 0.2.12 and 0.4.3 and they both seem to work, you may want to expand to safe >= 0.2.12 && < 0.5.
NOTE: A common mistake that crops up is that in a future version of your package, you forget to check compatibility with older versions, and it turns out you're using a new featured introduced in say safe-0.4.1, making the old bounds invalid. There's unfortunately not much in the way of automated tooling to check for this.
Just forget all of it: no version bounds at all, and make it the responsibility of the consumer of the package to ensure compatibility in a build plan. This has the downside that it's possible to create invalid build plans, but the upside that your bounds won't eliminate potentially good ones. (This is basically a false positive vs false negative tradeoff.)
The Stackage project runs nightly builds that can often let you know when your package is broken by new versions of dependencies, and make it easier for users to consume your package by providing pre-built snapshots that are known to work. This especially helps with case (3), and a little bit with the loose lower bounds in (2).
You may also want to consider using a Travis configuration the tests against old Stackage snapshots, e.g. https://github.com/commercialhaskell/stack/blob/master/doc/travis-complex.yml
I assume you're aware of the Haskell Package Versioning Policy (PVP). This provides some guidance, both implicitly in the meaning it assigns to the first three components of the version ("A.B.C") plus some explicit advice on Cabal version ranges.
Roughly speaking, future versions with the same "A.B" will not have introduced any breaking changes (including introducing orphan instances that might change the behavior of other code), but might have added new bindings, types, etc. Provided you have used only qualified imports or explicit import lists:
import qualified Something as S
import Something (foo, bar)
you can safely write a dependency of the form:
something >= 1.2.0 && < 1.6
where the assumption would be that you've tested 1.2.0 through 1.5.6, say, and you're confident that it'll continue to run with all future 1.5.xs (non-breaking changes) but could conceivably break on a future 1.6.
If you have imported a package unqualified (which you might very well do if you are re-exporting a big chunk of its API), you'll want a variant of:
the-package >= 1.2.0 && < 1.5.4 -- tested up to 1.5.3 API
the-package >= 1.5.3 && < 1.5.4 -- actually, this API precisely
There is also a caveat (see the PVP) if you define an orphan instance.
Finally, when importing some simple, stable packages where you've imported only the most obviously stable components, you could probably make the assumption that:
the-package >= 1.2.0 && < 2
is going to be pretty safe.
Looking at the Cabal file for a big, complex, well-written package might give you some sense of what's done in practice. The lens package, for example, extensively uses dependencies of the form:
array >= 0.3.0.2 && < 0.6
but has occasional dependencies like:
free >= 4 && < 6
(In many cases, these broader dependencies are on packages written by the same author, and he can obviously ensure that he doesn't break his own packages, so can be a little more lax.)
The purpose of the bounds is to ensure the version of the dependency you use has the feature(s) that you need. There is some earliest version X that introduces all those features, so you need a lower bound that is at least X. It's possible that a required feature is removed from a later version Y, in which case you would need to specify an upper bound that is less than Y:
build-depends: foo >= X && < Y
Ideally, a feature you need never gets removed, in which case you can drop the upper bound. This means the upper bound is only needed if you know your feature disappears from a later version. Otherwise, assume that foo >= X is sufficient until you have evidence to the contrary.
foo == X should rarely be used; it is basically short for foo >= X && <= X, and states that you are using a feature that is only in version X; it wasn't in earlier versions, and it was removed in a later version. If you find yourself in such a situation, it would probably be better to try to rewrite your code to not rely on that feature anymore, so that you can return to using foo >= Z (by relaxing the requirement for version X exactly, you may be able to get by with an even earlier version Z < X of foo).
A “foolproof” answer would be: allow exactly those versions that you're sure will work successfully! If you've only ever compiled your project with safe-0.3.15, then technically speaking you don't know whether it'll also work with safe-0.3.15, thus the constraint that cabal offers is right. If you want compatibility with other versions, test them by successively going backwards. This can be done easiest by completely disabling the constraint in the .cabal file and then doing
$ cabal configure --constraint='safe==XYZ' && cabal test
For each version XYZ = 0.3.14 etc..
Practically speaking, that's a bit of a paranoid approach. In particular, it's good etiquette for packages to follow the Package Versioning Policy, which demands that new minor versions should never break any builds. I.e., if 0.3.15 works, then 0.3.16 etc. should at any rate work too. So the conservative constraint if you've only checked 0.3.15 would actually be safe >=0.3.15 && <0.4. Probably, safe >=0.3 && <0.4 would be safe† too. The PVP also requires that you don't use looser major-version bounds than you can confirm to work, i.e. it mandates the <0.4 constraint.
Often, this is still needlessly strict. It depends on how tightly you work with some package. In particular, sometimes you'll need to explicitly depend on a package just for some extra configuration function of a type used by a more important dependency. In such a case, I tend to not give any bounds at all for the ancillary package. For an extreme example, if I depend on diagrams-lib, that there's no good reason to give any bounds to diagrams-core, because that is anyway coupled to diagrams-lib.
I also don't usually bother with bounds for very stable and standard packages like containers. The exception is of course base.
†Did you have to pick the safe package as an example?
In the dependencies section of a cabal file:
Build-Depends: base >= 3 && < 5, transformers >= 0.2.0
Should I be doing something like
Build-Depends: base >= 3 && < 5, transformers >= 0.2.0 && < 0.3.0
(putting upper limits on versions of packages I depend on)
or not?
I'll use a real example: my "List" package on Hackage (List monad transformer and class)
If I don't put the limit - my package could break by a change in "transformers"
If I do put the limit - a user that uses "transformers" but is using a newer version of it will not be able to use lift and liftIO with ListT because it's only an instance of these classes of transformers-0.2.x
I guess that applications should always put upper limits so that they never break, so this question is only about libraries:
Shall I use the upper version limit on dependencies or not?
There is an explicit policy recommending upper bounds - see in particular section 3 ("Dependencies in Cabal"). The other answers give some further justification for this policy.
In short - the upper limit should be in form of < A.(B+1) where A and B are the first elements of the current version (A.B.C...). This is because increasing A.B should mean that the version breaks old APIs.
Think about the failure modes:
With the upper bound, either your package builds or cabal bleats about an unsatisfied build dependency. Blame is clearly assigned.
Without the upper bound, customer has a recent version of transformers and it's not backwards compatible. Your software fails to build; GHC bleats about how your code doesn't compile. Your software looks shoddy.
Put in the upper bound.
IMO putting upper bounds on the accepted version numbers is the right thing to do. Given the semantics of version numbers used by Hackage there is certainly no guarantee that your package will work with, in this case, transformers 0.3.0.
I haven't seen any real discussion about this though and there doesn't seem to be a general recommendation to use upper bounds except for the base package.