Seq1 migration issue?

[StefanBertels]

Release https://github.com/louthy/language-ext/releases/tag/v4.0.2 changed static constructor function Seq1 to Seq.

I fully suport this decision as Seq1 always felt like "wrong" or like a workaround.

But I just want to point out some issue that might occur when upgrading existing code to this new release.
IMO a good way to migrate is via compile time errors (maximum safety).
Of course there are other options like [Obsolete] which might be helpful.

I guess there are relevant use cases out there that might not result in compile time errors. This might produce bugs if users don't take special care (i.e. don't read release notes or maybe even ignore warnings about obsolete functions).

Here's some test that will fail on 4.0.2 (but not 3.4.15).

[Fact]
void Bad()
{
    var data = LanguageExt.Prelude.Seq<int>();
    var x = LanguageExt.Prelude.Seq(data); // breaking change
    Assert.True(x.IsEmpty);
}

One idea for a safe migration path: Create some 3.4.16 (stable) release and another 3.x beta release where single parameter Seq(x) function is missing completely (forcing migration to toSeq when updating to this intermediate version).

There are other options using [Obsolete] and/or slow migration releases but IMO they are not appropriate for an OSS library like this (and maybe not safe).

[louthy]

I think this is a fair point. What I might do is just remove the Seq constructor function, and resurrect Seq1. Seq1 was the thing that bothered me the least about this, it was the fact that Seq was used as both a constructor function and a conversion function.

There are other options using [Obsolete] and/or slow migration releases but IMO they are not appropriate for an OSS library like this (and maybe not safe)

I think a migration approach would be simpler to be honest. If I migrate the conversion functions now (to toSeq), and keep Seq1, that will force a migration of the conversion functions. Then 6 months or so I can convert Seq1, that should give everyone enough time to get to v4 and be ready for the switch. For those that are really slow to migrate, there's a risk, but if I tag the releases and have it documented, then they can stage their upgrade in their own time.

[StefanBertels]

Totally agree.