FSharp.Compiler.Service v34.0 seems to have had a breaking API change

[SteveGilham]

Description

After updating a Fake script to v5.19.1 from v5.19 (which updated from FSharp.Compiler.Service (33.0.1) to FSharp.Compiler.Service (34.0.1)) and incidentally FSharpLint.Core from 0.12.5 to 0.12.10, the linting operation failed with exception

System.MissingMethodException: Method not found: 'FSharp.Compiler.SourceCodeServices.FSharpChecker FSharp.Compiler.SourceCodeServices.FSharpChecker.Create(Microsoft.FSharp.Core.FSharpOption`1<Int32>, Microsoft.FSharp.Core.FSharpOption`1<Boolean>, Microsoft.FSharp.Core.FSharpOption`1<Boolean>, Microsoft.FSharp.Core.FSharpOption`1<Resolver>, Microsoft.FSharp.Core.FSharpOption`1<Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<System.String,System.DateTime>,Microsoft.FSharp.Core.FSharpOption`1<System.Tuple`3<System.Object,IntPtr,Int32>>>>, Microsoft.FSharp.Core.FSharpOption`1<Boolean>)'.
           at FSharpLint.Application.Lint.lintFile(OptionalLintParameters optionalParams, String filepath)

Repro steps

Use the package versions specified above and run a Fake target like

_Target "Lint" (fun _ ->
  let failOnIssuesFound (issuesFound: bool) =
    Assert.That(issuesFound, Is.False, "Lint issues were found")
  try
    let settings =
      Configuration.SettingsFileName
      |> Path.getFullName
      |> File.ReadAllText

    let lintConfig =
      FSharpLint.Application.ConfigurationManagement.loadConfigurationFile settings
    let options =
      { Lint.OptionalLintParameters.Default with Configuration = Some lintConfig }

    !!"**/*.fsproj"
    |> Seq.collect (fun n -> !!(Path.GetDirectoryName n @@ "*.fs"))
    |> Seq.distinct
    |> Seq.map (fun f ->
         match Lint.lintFile options f with
         | Lint.LintResult.Failure x -> failwithf "%A" x
         | Lint.LintResult.Success w ->
           w
           |> Seq.filter (fun x ->
                match x.Fix with
                | None -> false
                | Some fix -> fix.FromText <> "AltCover_Fake")) // special case
    |> Seq.concat
    |> Seq.fold (fun _ x ->
         printfn "Info: %A\r\n Range: %A\r\n Fix: %A\r\n====" x.Info x.Range x.Fix
         true) false
    |> failOnIssuesFound
  with ex ->
    printfn "%A" ex
    reraise())

Expected behavior

Linting happens

Actual behavior

Exception thrown as above

Known workarounds

Back off to previous tool versions.

Related information

• Operating system - Windows
• Branch - NuGet released package
• .NET Runtime, CoreCLR or Mono Version - .net core 3.1.101

[duckmatt]

Thank you for the report, hopefully we should be on the updated fcs in the next day or so

[SteveGilham]

Still reproduces on v0.13.0

System.MissingMethodException: Method not found: 'FSharp.Compiler.SourceCodeServices.FSharpChecker FSharp.Compiler.SourceCodeServices.FSharpChecker.Create(Microsoft.FSharp.Core.FSharpOption`1<Int32>, Microsoft.FSharp.Core.FSharpOption`1<Boolean>, Microsoft.FSharp.Core.FSharpOption`1<Boolean>, Microsoft.FSharp.Core.FSharpOption`1<Resolver>, Microsoft.FSharp.Core.FSharpOption`1<Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<System.String,System.DateTime>,Microsoft.FSharp.Core.FSharpOption`1<System.Tuple`3<System.Object,IntPtr,Int32>>>>, Microsoft.FSharp.Core.FSharpOption`1<Boolean>)'.
           at FSharpLint.Application.Lint.lintFile(OptionalLintParameters optionalParams, String filepath)

with the fake task modified to take the FSharpLint API changes into account

_Target "Lint" (fun _ ->
  let failOnIssuesFound (issuesFound: bool) =
    Assert.That(issuesFound, Is.False, "Lint issues were found")
  try
    let settings =
      Configuration.SettingsFileName
      |> Path.getFullName
      |> File.ReadAllText

    let lintConfig =
      FSharpLint.Application.ConfigurationManagement.loadConfigurationFile settings
    let options =
      { Lint.OptionalLintParameters.Default with Configuration = Some lintConfig }

    !!"**/*.fsproj"
    |> Seq.collect (fun n -> !!(Path.GetDirectoryName n @@ "*.fs"))
    |> Seq.distinct
    |> Seq.map (fun f ->
         match Lint.lintFile options f with
         | Lint.LintResult.Failure x -> failwithf "%A" x
         | Lint.LintResult.Success w ->
           w
           |> Seq.filter (fun x ->
                match x.Details.SuggestedFix with
                | Some l -> match l.Force() with
                            | Some fix -> fix.FromText <> "AltCover_Fake" // special case
                            | _ -> false
                | _ -> false))
    |> Seq.concat
    |> Seq.fold (fun _ x ->
         printfn "Info: %A\r\n Range: %A\r\n Fix: %A\r\n====" x.Details.Message x.Details.Range x.Details.SuggestedFix
         true) false
    |> failOnIssuesFound
  with 
  | :? System.NullReferenceException ->
    printfn "MissingMethodException raised"
  | ex ->
    printfn "%A" ex
    reraise()
    )

[SteveGilham]

Is it possible that something flaky is going on with optional arguments in this Create call?

Adding

    let where = typeof<FSharp.Compiler.SourceCodeServices.FSharpChecker>.Assembly
    printfn "%A" (where.GetName())
    typeof<FSharp.Compiler.SourceCodeServices.FSharpChecker>.GetMethods()
    |> Seq.iter (fun m -> printfn "%A" m.Name)
    typeof<FSharp.Compiler.SourceCodeServices.FSharpChecker>.GetMethod("Create").GetParameters()
    |> Seq.iter (fun m -> printfn "%A" m)

ahead of the Lint.lintFile yields

FSharp.Compiler.Service, Version=34.1.0.0, Culture=neutral, PublicKeyToken=null
"Create"
"MatchBraces"
...
Microsoft.FSharp.Core.FSharpOption`1[System.Int32] projectCacheSize
Microsoft.FSharp.Core.FSharpOption`1[System.Boolean] keepAssemblyContents
Microsoft.FSharp.Core.FSharpOption`1[System.Boolean] keepAllBackgroundResolutions
Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.ReferenceResolver+Resolver] legacyReferenceResolver
Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpFunc`2[System.Tuple`2[System.String,System.DateTime],Microsoft.FSharp.Core.FSharpOption`1[System.Tuple`3[System.Object,System.IntPtr,System.Int32]]]] tryGetMetadataSnapshot  
Microsoft.FSharp.Core.FSharpOption`1[System.Boolean] suggestNamesForErrors
Microsoft.FSharp.Core.FSharpOption`1[System.Boolean] keepAllBackgroundSymbolUses
Microsoft.FSharp.Core.FSharpOption`1[System.Boolean] enableBackgroundItemKeyStoreAndSemanticClassification

with 2 trailing option bool arguments above and beyond the ones in the missing method signature.

[SteveGilham]

More digging -- root cause is that the compiler services assembly doesn't do semantic versioning properly, if at all.

Decompiling the v34.1 compiler services assembly shows that whether by design or oversight there's a parameter not marked as [OptionalArgument], though the .fsi file check in that added the 2 new arguments marks all arguments with a leading ? --

public static FSharpChecker Create([OptionalArgument] FSharpOption<int> projectCacheSize,
 [OptionalArgument] FSharpOption<bool> keepAssemblyContents,
 [OptionalArgument] FSharpOption<bool> keepAllBackgroundResolutions,
 [OptionalArgument] FSharpOption<ReferenceResolver.Resolver> legacyReferenceResolver,
 [OptionalArgument] FSharpOption<FSharpFunc<Tuple<string, DateTime>,
 FSharpOption<Tuple<object, IntPtr, int>>>> tryGetMetadataSnapshot,
 [OptionalArgument] FSharpOption<bool> suggestNamesForErrors,
 [OptionalArgument] FSharpOption<bool> keepAllBackgroundSymbolUses, 
[OptionalArgument] FSharpOption<bool> enableBackgroundItemKeyStoreAndSemanticClassification)

while decompiling the Create() call in FSharpLint 0.13.0 shows it's expanded to the missing method signature with fewer trailing arguments

	FSharpChecker checker = FSharpChecker.Create((FSharpOption<int>)null,
 (FSharpOption<bool>)null,
 (FSharpOption<bool>)null,
 (FSharpOption<Resolver>)null,
 (FSharpOption<FSharpFunc<Tuple<string, DateTime>, FSharpOption<Tuple<object, IntPtr,
 int>>>>)null,
 (FSharpOption<bool>)null);
``

[jgardella]

Awesome @SteveGilham, thanks for investigating. #378 to update FCS to v34.0.1 is still in review, I think let's wait until that gets merged and we push a new version, and see if it resolves the issue. If it doesn't we can continue investigating, and maybe reach out to the FCS maintainers.

[baronfel]

apologies for the API slippage on FCS, I missed this API in the merge. I've got an action item to add usage of the dotnet synver tool to the build process to help decide on what the correct version bump should be.

[jgardella]

Assuming this is fixed in FCS v34.0.1, v0.13.2 shouldn't have this issue. Appreciate if you could confirm @SteveGilham.

[baronfel]

Thanks to this issue in part I've added new checks to the FCS build and deploy pipeline that ensure we follow semver rules. Thanks for raising the alarm, @SteveGilham!

[SteveGilham]

This issue no longer reproduces with 0.13.2, now that I've tracked the FSharpLint API change between 0.13.1 and 0.13.2.