Fable: Support for implicit yields

[Shmew]

The addition of implicit yields sounds really nice for Fable, as sure enough they mentioned it. Is there a thread or issue I can track to see when Fable will support this functionality? Testing it this morning gave me compile errors.

[ncave]

Looks like the new language features were merged into dotnet/fsharp master yesterday but there are still some build issues. I can rebase to latest from it once it gets to green. It will be a new Fable compiler version, once it's released.

[ncave]

@alfonsogarciacaro fcs-fable is rebased to latest, so we can begin experimenting with the new features, hopefully they don't require (m)any changes in Fable.

[alfonsogarciacaro]

Thanks @ncave! I'm getting an error when trying to build latest service_slim fable branch in your fsharp fork. Do you know what it could be?

     1>FSC : warning FS0075: The command-line option '--version' has been deprecated [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
     1>/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018: The "CreateAppHost" task failed unexpectedly. [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018: System.IO.IOException: The target file '/Users/alfonsogarciacaronunez/dev/fsharp_fable/artifacts/obj/fcs/netcoreapp3.0/codegen' is a directory, not a file. [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at System.IO.FileSystem.CopyFile(String sourceFullPath, String destFullPath, Boolean overwrite) [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at System.IO.File.Copy(String sourceFileName, String destFileName, Boolean overwrite) [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at Microsoft.NET.HostModel.AppHost.BinaryUtils.CopyFile(String sourcePath, String destinationPath) [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at Microsoft.NET.HostModel.AppHost.HostWriter.CreateAppHost(String appHostSourceFilePath, String appHostDestinationFilePath, String appBinaryFilePath, Boolean windowsGraphicalUserInterface, String assemblyToCopyResorcesFrom) [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at Microsoft.NET.Build.Tasks.CreateAppHost.ExecuteCore() [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at Microsoft.NET.Build.Tasks.TaskBase.Execute() [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]
/usr/local/share/dotnet/sdk/3.0.100/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(370,5): error MSB4018:    at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask) [/Users/alfonsogarciacaronunez/dev/fsharp_fable/fcs/fcs-fable/codegen/codegen.fsproj]

[alfonsogarciacaro]

Sorry, actually service_slim did build fine. The error was about the fable branch, I've updated the comment above ☝️

[alfonsogarciacaro]

It works! (unfortunately not in the REPL yet until we fixed the issue with fcs-fable).

I've pushed fable-compiler 2.4.0 with support for implicit yields and other F# 4.7 features, thanks again @ncave!

[michaelsg]

It seems that fable-compiler 2.4.1 is missing its binfable-cli folder.
fable-compiler 2.4.0 works.

$ webpack
Bundling for development...
fable-compiler 2.4.1
child proccess errored: Could not execute because the specified command or file was not found.
Possible reasons for this include:
  * You misspelled a built-in dotnet command.
  * You intended to execute a .NET Core program, but dotnet-C:\Code2019\Src\FCSTools_Solution\XUI\node_modules\fable-compiler\bin\fable-cli\Fable.Cli.dll does not exist.

[alfonsogarciacaro]

Yeah, I just realized that 😅 Can you please try with 2.4.2?

[michaelsg]

2.4.2 works! Love it!