Type Providers design assembly required without direct reference.

[matthid]

Repro steps

Provide the steps required to reproduce the problem

1. git clone https://github.com/matthid/fcs_bug_585.git
2. cd fcs_bug_585
3. ./build.sh (git bash) or build.cmd

What this does is:

1. Create library LibraryUsingTypeprovider with the following contents

   namespace LibraryUsingTypeprovider
   
   // This is only here, because otherwise the F# compiler is smart enough to optimize the reference away...
   open FSharp.Data
   open FSharp.Data.JsonExtensions
   
   module Wrapped =
   let useSomething (j : JsonValue) =
     j?Major.AsInteger()

   with a reference to FSharp.Data

2. Create a console application Repro with

   open System
   open System.IO
   open System.Reflection
   
   let scriptFilePath = Path.GetFullPath @"myscript.fsx"
   // replace with path to the compiled LibraryUsingTypeprovider library.
   let someLib = Path.GetFullPath @"C:\PROJ\FSharp.Compiler.Service_585\bin/lib/LibraryUsingTypeprovider.dll"
   File.WriteAllText(scriptFilePath, @"
   #r """ + someLib.Replace(@"\", @"\\") + @"""
   open System
   Console.WriteLine(""TEST_OUTPUT"")");
   open Microsoft.FSharp.Compiler.Interactive.Shell
   
   [<EntryPoint>]
   let main args =
   let fsiConfig = FsiEvaluationSession.GetDefaultConfiguration()
   let fsiArgs = [| @"C:\fsi.exe" |]
   let inStream = new StringReader("")
   use session = FsiEvaluationSession.Create(fsiConfig, fsiArgs, inStream, Console.Out, Console.Error)
   session.EvalScriptNonThrowing scriptFilePath |> printfn "%A"
   //execScript scriptFilePath
   0

   with references to FSharp.Compiler.Service and LibraryUsingTypeprovider.

3. Run Repro.exe

Expected behavior

Starting Target: RunRepro (==> BuildRepro)
bin/repro/Repro.exe

F# Interactive for F# 4.0 (private)
Freely distributed under the Apache 2.0 Open Source License

For help type #help;;

> [Loading C:\PROJ\FSharp.Compiler.Service_585\myscript.fsx]
TEST_OUTPUT
(Choice1Of2 null, [||])

Actual behavior

Starting Target: RunRepro (==> BuildRepro)
bin/repro/Repro.exe

F# Interactive for F# 4.0 (private)
Freely distributed under the Apache 2.0 Open Source License

For help type #help;;

> [Loading C:\PROJ\FSharp.Compiler.Service_585\myscript.fsx]
Stopped due to error
(Choice2Of2
   System.Exception: Operation could not be completed due to earlier error,
 [|C:\PROJ\FSharp.Compiler.Service_585\myscript.fsx (2,1)-(2,83) parse error The type provider 'C:\PROJ\FSharp.Compiler.Service_585\bin\repro\FSharp.Data.dll' reported an error: Assembly attribute 'TypeProviderAssemblyAttribute' refers to a designer assembly 'FSharp.Data.DesignTime' which cannot be loaded or doesn't exist. Could not load file or assembly 'file:///C:\PROJ\FSharp.Compiler.Service_585\bin\repro\FSharp.Data.DesignTime.dll' or one of its dependencies. The system cannot find the file specified.;
   C:\PROJ\FSharp.Compiler.Service_585\myscript.fsx (2,1)-(2,83) parse warning Referenced assembly 'C:\PROJ\FSharp.Compiler.Service_585\bin\repro\FSharp.Data.dll' has assembly level attribute 'Microsoft.FSharp.Core.CompilerServices.TypeProviderAssemblyAttribute' but no public type provider classes were found|])

Known workarounds

• Bundling the type provider design assembly should work
• Removing the reference in Repro to LibraryUsingTypeprovider seems to work as well (matthid/fcs_bug_585@a36921b).

Related information

• Windows 10
• FSharp.Compiler.Service 3.0.0.0 Release (2.0.0.6 has same behavior)
• .NET Runtime 4.6
• VS 2015

I couldn't reproduce this with the fsi -> When running the failing code within fsi everything seems to work as expected.

--- Initial Report

In fsprojects/FAKE#1274 I noticed that design assemblies of type providers seem to be required, even for indirect references, even when the code trying to compile is not using the type provider at all.

Is this by design or a bug? If it is a bug I can try to create a repro for it. Shouldn't the F# compiler only request the design-assembly when it's needed (lazily)?

I'm not sure if this happens with the regular compiler as well (it probably isn't as much of a problem there as with nuget we have the design assemblies available, even for indirect dependencies), but for now this was detected by using FSharp.Compiler.Service.

[dsyme]

Could you follow https://github.com/fsharp/FSharp.Compiler.Service/blob/master/ISSUE_TEMPLATE.md and submit a standalone repro with expected/actual steps please.

Thanks!
Don

[matthid]

Yeah sure, but I think this isn't easy to reproduce. So when anyone can quickly say if this sounds like a bug or not, it would save me quite some time ... Should the design assembly be needed when the code to compile doesn't use the type provider directly (for example via indirect dependencies)? If yes there is no point reproducing this.

Thanks for your fast answer.

[matthid]

Updated the first comment with repro steps.