Cannot generate usable interfaces

[panesofglass]

Description

I ran into the following problems while trying to generate interfaces in the generative SwaggerProvider:

• Cannot generate an interface using ProvidedTypeDefinition that will load at runtime.
• Cannot generate valid interface methods on a ProvidedTypeDefinition. ProvidedMethod requires invokeCode, which appears to be converting the generated method into a public extern method.

Repro steps

Please provide the steps required to reproduce the problem

1. Clone https://github.com/panesofglass/SwaggerProvider and switch to the api-interfaces branch.

2. Run git reset --hard bb2a984101f767b689e49ed63ee38bfd607ffe89 to get to the interfaces implementation.

3. Run build.cmd to run the FAKE build.

4. Observe that, just after starting RunUnitTests, the program breaks with the following error:

5. Comment out generation of the interfaces to observe that the type provider runs tests successfully: https://github.com/panesofglass/SwaggerProvider/blob/api-interfaces/src/SwaggerProvider.DesignTime/SwaggerProviderConfig.fs#L89

6. To see the ProvidedMethod issue, roll back to this commit and run the build, then inspect the generated SwaggerProvider.ProvidedTests assembly for the Swagger.PetStore.Tests.PetStore.Contract type.

Expected behavior

1. ProvidedTypeDefinition with TypeAttributes.Public ||| TypeAttributes.Interface ||| TypeAttributes.Abstract attributes should generate an interface that can be loaded at runtime.

2. Generated interfaces should be able to contain generated methods.

3. Generated interfaces should be implementable by user types.

4. Generated interfaces should be implementable on generated types within the type provider.

Actual behavior

1. Runtime fails to load the generated interface type, causing, in this case a test assembly, to crash even when the generated interface is not used.

2. Generated interface methods are not public abstract method but public extern method.

Known workarounds

None.

Additional information

• This PR shows the sequence of steps I've tried and includes a fork of ProvidedTypes.fs and ProvidedTypes.fsi that attempted to make the invokeCode parameter on ProvidedMethod optional.

[panesofglass]

This situation also appears to be true when trying to generate an abstract class with abstract methods, though it seems to only be the methods in this case. See panesofglass/SwaggerProvider@983b1a3

[panesofglass]

I found a potential work-around using an abstract class with virtual methods, but the generated methods once again appear incorrect:

Based on other abstract classes such as System.IO.TextReader, that should be a public virtual method:

See panesofglass/SwaggerProvider@d88ba1c

[panesofglass]

I am happy to help sort these into different bugs and work on smaller repros, if that's useful, but I'll need some help, at least for the first one.

[panesofglass]

I think I can add tests to show these are not working properly. I’ll try to get them properly failing and submit a PR, if that is useful.

[thinkbeforecoding]

I think this has been fixed by #311
We may close this

[cartermp]

Thanks, will close.