Can't generate contoso project with typespec-csharp

[catalinaperalta]

Describe the issue or request
Someone from the API mgmt team tried to run tsp-client init -c https://github.com/Azure/azure-rest-api-specs/blob/431eb865a581da2cd7b9e953ae52cb146f31c2a6/specification/contosowidgetmanager/Contoso.WidgetManager/tspconfig.yaml in the azure-sdk-for-net repo and ran into the following emitter issue:

C:\Users\caperal\repos\azure-sdk-for-net> tsp-client init -c https://github.com/Azure/azure-rest-api-specs/blob/431eb865a581da2cd7b9e953ae52cb146f31c2a6/specification/contosowidgetmanager/Contoso.WidgetManager/tspconfig.yaml
Use output directory 'C:/Users/caperal/repos/azure-sdk-for-net'? (y/n) 
Using output directory 'C:/Users/caperal/repos/azure-sdk-for-net'

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tsp-client version: 0.8.1
Found emitter package @azure-tools/typespec-csharp
SDK initialized in C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso
Processing additional directory: specification/contosowidgetmanager/Contoso.WidgetManager.Shared
Syncing additional directory: specification/contosowidgetmanager/Contoso.WidgetManager.Shared
Found emitter package @azure-tools/typespec-csharp
Installing dependencies from npm...

added 85 packages, and audited 86 packages in 3s

12 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities
Resolved path: C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso/TempTypeSpecFiles/Contoso.WidgetManager/node_modules/@typespec/compiler
Compiling tsp using @azure-tools/typespec-csharp...
Unhandled exception. System.Exception: Unknown type
   at AutoRest.CSharp.Generation.Types.TypeFactory.CreateType(InputType inputType) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\Generation\Types\TypeFactory.cs:line 92
   at AutoRest.CSharp.Output.Models.OperationMethodChainBuilder.GetLongRunningResultRetrievalMethod(OperationLongRunning longRunning) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\Output\OperationMethodChainBuilder.cs:line 174
   at AutoRest.CSharp.Output.Models.OperationMethodChainBuilder.BuildOperationMethodChain() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\Output\OperationMethodChainBuilder.cs:line 115
   at AutoRest.CSharp.Output.Models.LowLevelClient.BuildMethods(LowLevelClient client, TypeFactory typeFactory, IEnumerable`1 operations, ClientFields fields, String namespaceName, String clientName, SourceInputModel sourceInputModel)+MoveNext() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\Output\LowLevelClient.cs:line 131
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at AutoRest.CSharp.Output.Models.LowLevelClient.get_AllClientMethods() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\Output\LowLevelClient.cs:line 95
   at AutoRest.CSharp.Output.Models.LowLevelClient.get_ClientMethods() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\Output\LowLevelClient.cs:line 98
   at AutoRest.CSharp.LowLevel.Output.Samples.DpgClientSampleProvider..ctor(String defaultNamespace, LowLevelClient client, SourceInputModel sourceInputModel) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\Output\Samples\DpgClientSampleProvider.cs:line 30
   at AutoRest.CSharp.Output.Models.Types.DpgOutputLibrary.EnsureDpgSampleProviders() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\AutoRest\DpgOutputLibrary.cs:line 110
   at AutoRest.CSharp.Output.Models.Types.DpgOutputLibrary.get_DpgClientSampleProviders() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\AutoRest\DpgOutputLibrary.cs:line 98
   at AutoRest.CSharp.Output.Models.Types.DpgOutputLibrary.GetSampleForClient(LowLevelClient client) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\AutoRest\DpgOutputLibrary.cs:line 119
   at AutoRest.CSharp.AutoRest.Plugins.LowLevelTarget.ExecuteAsync(GeneratedCodeWorkspace project, InputNamespace inputNamespace, SourceInputModel sourceInputModel, Boolean isTspInput) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\LowLevel\AutoRest\LowLevelTarget.cs:line 43
   at AutoRest.CSharp.AutoRest.Plugins.CSharpGen.ExecuteAsync(InputNamespace rootNamespace) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\Plugins\CSharpGen.cs:line 104
   at AutoRest.CSharp.AutoRest.Communication.StandaloneGeneratorRunner.RunAsync(CommandLineOptions options) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\Communication\StandaloneGeneratorRunner.cs:line 51
   at AutoRest.CSharp.Program.Run(CommandLineOptions options) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Program.cs:line 47
   at AutoRest.CSharp.Program.<>c.<<Main>b__2_0>d.MoveNext() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Program.cs:line 29
--- End of stack trace from previous location ---
   at AutoRest.CSharp.Program.Main(String[] args) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Program.cs:line 26     
   at AutoRest.CSharp.Program.<Main>(String[] args)
ExternalError: Emitter "@azure-tools/typespec-csharp" crashed! This is a bug.
Please file an issue at https://github.com/Azure/autorest.csharp/issues

Error: Command failed: dotnet --roll-forward Major C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso/TempTypeSpecFiles/Contoso.WidgetManager/node_modules/@autorest/csharp/AutoRest.CSharp.dll --project-path C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso --new-project  --clear-output-folder true      
    at checkExecSyncError (node:child_process:890:11)
    at execSync (node:child_process:962:15)
    at Object.$onEmit [as emitFunction] (file:///C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso/TempTypeSpecFiles/Contoso.WidgetManager/node_modules/@azure-tools/typespec-csharp/dist/src/emitter.js:106:21)       
    at async runEmitter (file:///C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso/TempTypeSpecFiles/Contoso.WidgetManager/node_modules/@typespec/compiler/dist/src/core/program.js:555:13)
    at async compile (file:///C:/Users/caperal/repos/azure-sdk-for-net/sdk/contosowidgetmanager/Azure.Template.Contoso/TempTypeSpecFiles/Contoso.WidgetManager/node_modules/@typespec/compiler/dist/src/core/program.js:237:9)
    at async compileTsp (file:///C:/Users/caperal/AppData/Roaming/npm/node_modules/@azure-tools/typespec-client-generator-cli/dist/typespec.js:76:21)
    at async generate (file:///C:/Users/caperal/AppData/Roaming/npm/node_modules/@azure-tools/typespec-client-generator-cli/dist/index.js:204:5)
    at async main (file:///C:/Users/caperal/AppData/Roaming/npm/node_modules/@azure-tools/typespec-client-generator-cli/dist/index.js:277:17)

--------------------------------------------------
Library Version                0.2.0-beta.20240614.3
TypeSpec Compiler Version      0.56.0
--------------------------------------------------

Describe your ideas for solutions
I would expect the contoso project in the azure-rest-api-specs repo to be able to be generated with the csharp emitter.

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[catalinaperalta]

cc @lirenhe @chunyu3

[chunyu3]

hello @catalinaperalta The error show that there is a type which is not supported. Would you please provide the spec used for us to investigate? thanks

[catalinaperalta]

Here it is: https://github.com/Azure/azure-rest-api-specs/tree/main/specification/contosowidgetmanager

[chunyu3]

The root cause is that the ReturnType of LRO operation is null but the ResultPath is not null. @archerzz would you please help on this? thanks

[archerzz]

The root cause is the @pollingOperation: https://github.com/Azure/azure-rest-api-specs/blob/934f8b595b6aba70096c6fd19089c3986b344c0c/specification/contosowidgetmanager/Contoso.WidgetManager/main.tsp#L53C29-L53C53

@pollingOperation(Widgets.getWidgetOperationStatus)

Widgets.getWidgetOperationStatus is defined as a polling with return value: https://github.com/Azure/azure-rest-api-specs/blob/934f8b595b6aba70096c6fd19089c3986b344c0c/specification/contosowidgetmanager/Contoso.WidgetManager/main.tsp#L46

getWidgetOperationStatus is GetResourceOperationStatus<WidgetSuite>;

So, the LroMetadata contains ResultPath (because you have a resource polling), but no ReturnType (because its delete).

[archerzz]

@catalinaperalta I created a PR to fix the problematic spec: Azure/azure-rest-api-specs#30012

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