Improve signature of defaultWith

[edgarfgp]

Click “Files changed” → “⋯” → “View file” for the rendered RFC.

Based on @gusty suggestion to improve the defaultWith signature : See : https://github.com/fsharp/fslang-suggestions/issues/1123#issuecomment-1179171067

• Will give us the opportunity to use the error value in the compensation.

[edgarfgp]

@cartermp would love to have a review please ?

[cartermp]

Thanks for the ping. I think this looks fine but would like @dsyme to give it a final look.

[vzarytovskii]

I don't remember if the current API was already released to nuget. If it did, this will technically be a breaking change (unit vs generic param).

[edgarfgp]

Hope we can fix this before released to nuget. If not we can add another function that adds this ? . I will more that happy to help either way :)

[cartermp]

@vzarytovskii I don't think it's in any shipped version, no. So there should be time? The PR that added the feature set was done in June 20th

[dsyme]

I'm ok with this as long as it hasn't been shipped to nuget

[vzarytovskii]

I'm ok with this as long as it hasn't been shipped to nuget

It hasn't been released as a nuget package but has been part of SDK/VS since June 20th(ish). Also, we have a beta package released about 2 weeks ago, as long as we fine with breaking betas, it's OK.

cc @KevinRansom

[cartermp]

By that you mean preview VS, right? Design changes like this are fine to make in previews I'd say (at least that's certainly the design for language and IDE features).

[witoldsz]

Is it just me, or did you change the type and meaning of the function, introducing a breaking change in F# programs?

My application stopped compiling when upgraded from F# 6

    [<CompiledName("DefaultWith")>]
    let defaultWith defThunk result =
        match result with
        | Error _ -> defThunk ()
        | Ok v -> v

to F# 7 with:

    [<CompiledName("DefaultWith")>]
    let defaultWith defThunk result =
        match result with
        | Error error -> defThunk error
        | Ok v -> v

[vzarytovskii]

Is it just me, or did you change the type and meaning of the function, introducing a breaking change in F# programs?

My application stopped compiling when upgraded from F# 6

    [<CompiledName("DefaultWith")>]

    let defaultWith defThunk result =

        match result with

        | Error _ -> defThunk ()

        | Ok v -> v

to F# 7 with:

    [<CompiledName("DefaultWith")>]

    let defaultWith defThunk result =

        match result with

        | Error error -> defThunk error

        | Ok v -> v

Are you sure you weren't using preview versions? It should only be a breaking change in previews.

[gusty]

@witoldsz either that (previews) or maybe you are using FsToolkit

[witoldsz]

I am pretty sure the version with Error _ -> defThunk () is in official dotnet/F# 6 version.

Let me just check:

$ dotnet --version
6.0.417

$ dpkg -l |grep dotnet-sdk
ii  dotnet-sdk-6.0                              6.0.417-1                                   amd64        Microsoft .NET SDK 6.0.417

The issue came up when my colleague tried to upgrade services to work with dotnet 8 and one stopped compiling because of the new meaning of the Result.defaultWith.