fly launch does not recognize an F# project

[AngelMunoz]

Please only report specific issues with flyctl behavior. Anything like a support request for your application should go to https://community.fly.io. More people watch that space and can help you faster!

Describe the bug

F# web applications are not recognized as a .NET project even though they use the same tooling and build system as a C# application.

I followed the instructions given here https://fly.io/docs/languages-and-frameworks/dotnet/ but with the exception of using an F# project (.fsproj) rather than a C# project (.csproj)

• Operating system: Windows 11 26100.2033
• fly version: fly.exe v0.3.25 windows/amd64 Commit: 8fb314c BuildDate: 2024-10-21T16:49:16Z

** Command output: **

PS X:\> dotnet new web -lang F# -o Sample
The template "ASP.NET Core Empty" was created successfully.

Processing post-creation actions...
Restoring X:\Sample\Sample.fsproj:
  Determining projects to restore...
  Restored X:\Sample\Sample.fsproj (in 1.23 sec).
Restore succeeded.
PS X:\> cd Sample
PS X:\sample> dotnet run
Building...
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://localhost:5214
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
      Content root path: X:\sample
info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...
PS X:\sample> fly launch
Scanning source code
Could not find a Dockerfile, nor detect a runtime or framework from source code. Continuing with a blank app.
Warning: This organization has no payment method, turning off high availability
Creating app in X:\sample
We're about to launch your app on Fly.io. Here's what you're getting:

Organization: **************          (fly launch defaults to the personal org)
Name:         *************           (generated)
Region:       Stockholm, Sweden       (this is the fastest region for you)
App Machines: shared-cpu-1x, 1GB RAM  (most apps need about 1GB of RAM)
Postgres:     <none>                  (not requested)
Redis:        <none>                  (not requested)
Tigris:       <none>                  (not requested)
? Do you want to tweak these settings before proceeding? No
Warning: This organization has no payment method, turning off high availability
Created app '************' in organization 'personal'
Admin URL: ********
Hostname: *******
Wrote config file fly.toml
PS X:\sample>

Running the same with a C# project works as expected

PS X:\> dotnet new web -o Sample2
The template "ASP.NET Core Empty" was created successfully.

Processing post-creation actions...
Restoring X:\Sample2\Sample2.csproj:
  Determining projects to restore...
  Restored X:\Sample2\Sample2.csproj (in 144 ms).
Restore succeeded.


PS X:\> cd Sample2
PS X:\Sample2> dotnet run
Building...
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://localhost:5137
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
      Content root path: X:\Sample2
info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...
PS X:\Sample2> fly launch
Scanning source code
Detected a .NET app
Warning: This organization has no payment method, turning off high availability
Creating app in X:\Sample2
We're about to launch your .NET app on Fly.io. Here's what you're getting:

Organization: *********         (fly launch defaults to the personal org)
Name:         ********* (generated)
Region:       Stockholm, Sweden      (this is the fastest region for you)
App Machines: shared-cpu-1x, 1GB RAM (most apps need about 1GB of RAM)
Postgres:     <none>                 (not requested)
Redis:        <none>                 (not requested)
Tigris:       <none>                 (not requested)

? Do you want to tweak these settings before proceeding? No
Warning: This organization has no payment method, turning off high availability
Created app '*********' in organization 'personal'
Admin URL: ***********
Hostname: ***********
Wrote config file fly.toml
Validating X:\Sample2\fly.toml
✓ Configuration is valid
==> Building image

The culprit likely is in this file here:

flyctl/scanner/dotnet.go

Lines 12 to 14 in 8fb314c

	if !checksPass(sourceDir, dirContains("*.csproj", "Microsoft.NET.Sdk.Web")) {
	return nil, nil
	}

and

flyctl/scanner/dotnet.go

Lines 60 to 64 in 8fb314c

	if !info.IsDir() && filepath.Ext(path) == ".csproj" {
	csprojName = strings.TrimSuffix(info.Name(), ".csproj")
	csprojPath = path
	return filepath.SkipDir // Stop walking the directory
	}

where it is checking explicitly for *.csproj, both C# and F# (and even VB.NET) share the same file format and contents in the project files to truly support .NET apps (and not just C#) the glob/regex expresion should check for any of the *.fsproj, *.csproj (and even *.vbproj should work tbh same tooling) file formats instead as copying the files generated for the C# project in the F# project and then running fly deploy works as expected