Function.json generation failed (MetaGeneration)

[cboudereau]

Check for a solution in the Azure portal

After updating the Microsoft.NET.Sdk.Functions to 3.0.5 cleaning then building the project, an error occurs. I think the issue is connected to #4390 :

Investigative information

Function App version : V3, dotnet core 3.1

Repro steps

1. Create a new function
2. Use Custom routes with custom attributes
3. build the project

Expected behavior

Expected the function.json without msbuild errors.

Actual behavior

A build error is displayed :

Severity	Code	Description	Project	File	Line	Suppression State
Error		Mono.Cecil.AssemblyResolutionException: Failed to resolve assembly: 'Microsoft.Azure.WebJobs.Extensions.Http, Version=3.0.2.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
   at Mono.Cecil.BaseAssemblyResolver.Resolve(AssemblyNameReference name, ReaderParameters parameters)
   at Mono.Cecil.BaseAssemblyResolver.Resolve(AssemblyNameReference name)
   at Mono.Cecil.DefaultAssemblyResolver.Resolve(AssemblyNameReference name)
   at Mono.Cecil.MetadataResolver.Resolve(TypeReference type)
   at Mono.Cecil.ModuleDefinition.Resolve(TypeReference type)
   at Mono.Cecil.TypeReference.Resolve()
   at MakeFunctionJson.AttributeExtensions.IsWebJobsAttribute(CustomAttribute attribute)
   at MakeFunctionJson.ParameterInfoExtensions.<>c.<IsWebJobSdkTriggerParameter>b__0_0(CustomAttribute a)
   at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)
   at MakeFunctionJson.ParameterInfoExtensions.IsWebJobSdkTriggerParameter(ParameterDefinition parameterInfo)
   at MakeFunctionJson.MethodInfoExtensions.<>c.<HasTriggerAttribute>b__4_0(ParameterDefinition p)
   at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)
   at MakeFunctionJson.MethodInfoExtensions.HasTriggerAttribute(MethodDefinition method)
   at MakeFunctionJson.MethodInfoExtensions.HasValidWebJobSdkTriggerAttribute(MethodDefinition method)
   at MakeFunctionJson.FunctionJsonConverter.GenerateFunctions(IEnumerable`1 types)+MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at MakeFunctionJson.FunctionJsonConverter.TryGenerateFunctionJsons()
   at MakeFunctionJson.FunctionJsonConverter.TryRun()
Error generating functions metadata
	Gds.AzureFunctions	C:\Users\Clément\.nuget\packages\microsoft.net.sdk.functions\3.0.4\build\Microsoft.NET.Sdk.Functions.Build.targets	41	

Known workarounds

Pin the version of the Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator package to 1.1.5

[cboudereau]

If it can help, I analyzed the reason and after debugging with Mono.Cecil, the bin project directory contains the missed assembly in version 1.1.5 but not in 1.1.6.

After patching the Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator.targets by reverting the AfterTargets attribute from Build to _GenerateFunctionsPostBuild (Line 42, Target named _GenerateFunctionsExtensionsMetadataPostBuild), the assembly is available and Mono.Cecil finds the assembly.

Hi @brettsam, the targets fix (f987062) causes a potential regression here.

How can I help to solve this problem ?

[brettsam]

Can you share your project file? This is a known issue with 1.1.6 if you're directly referencing ExtensionsMetadataGenerator. but that should be very rare (there's no need to directly reference; the Sdk references it for you).

[cboudereau]

Hi @brettsam, first of all, thank you for your quick reply, I appreciate it.

I am not using directly this reference, I only reference the main package Microsoft.NET.Sdk.Functions.

The problem appears when you update the package, all inter dependencies are updated and the version 1.1.6 of the package Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator is used.

When you say it is a well known issue of the 1.1.6, would it be possible to have the issue number please so that we can contribute too ?

[brettsam]

I'm not seeing this when I use 3.0.5 -- would you still mind sharing your csproj file so I can try to repro this?

It's a known issue in the sense that I called it out during my commit to 1.1.6 -- we were having bigger issues so I thought that this was an okay risk for now (not assuming anyone using the Sdk would hit 1.1.6 unless they added a direct ref).

So let's use this issue as the tracking item for that.

[cboudereau]

Here is the repo where you can reproduce the problem : https://github.com/cboudereau/azurefunctionsample

I added the workaround in comments to quickly analyse the main differences between both versions