azure - F# Azure Function 的 Cosmos DB 绑定(bind)无法绑定(bind)

Question

我正在尝试在 F# 中创建一个具有 HTTP 触发器并从 Cosmos DB 检索数据的 Azure 函数。 documentation仅提供 C# 中的 CosmosDB 绑定(bind)示例，翻译代码会导致错误 Cannot bind parameter 'toDoItems' to type IEnumerable`1

这个 C# 示例能够记录 Cosmos 中项目的 id:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Host;
using System.Collections.Generic;
using Microsoft.Extensions.Logging;

namespace Customer
{
    public class ToDoItem
    {
        public string Id { get; set; }
        public string PartitionKey { get; set; }
        public string Description { get; set; }
    }

    public static class DocByIdFromQueryString
    {
        [FunctionName("Triggered")]
        public static IActionResult Run(
            [HttpTrigger(
                AuthorizationLevel.Anonymous,
                "get",
                Route = null
            )] HttpRequest req,
            [CosmosDB(
                databaseName: "customer-db",
                collectionName: "todo-collection",
                ConnectionStringSetting = "CosmosDBConnection",
                SqlQuery = "select * from c"
            )] IEnumerable<ToDoItem> toDoItems, ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            foreach (ToDoItem toDoItem in toDoItems)
            {
                log.LogInformation(toDoItem.Id);
            }
            return new OkResult();
        }
    }
}

这是工作 C# 代码的 F# 翻译。这两个示例具有相同的依赖项版本并使用相同的数据库(和连接字符串)。

namespace Customer

open Microsoft.AspNetCore.Http
open Microsoft.AspNetCore.Mvc
open Microsoft.Azure.WebJobs
open Microsoft.Azure.WebJobs.Extensions.Http
open Microsoft.Extensions.Logging


module CosmosBindings =
    type ToDoItem = {
        Id : string
        PartitionKey : string
        Description : string
    }

    [<FunctionName("HttpTrigger")>]
    let Run([<HttpTrigger(
                AuthorizationLevel.Anonymous,
                "get",
                Route = null
            )>] req: HttpRequest,
            [<CosmosDB(
                databaseName = "customer-db",
                collectionName = "todo-collection",
                ConnectionStringSetting = "CosmosDBConnection",
                SqlQuery = "select * from c"
            )>] toDoItems: ToDoItem seq) (log: ILogger) =
                log.LogInformation "F# HTTP trigger function processed a request."

                toDoItems
                |> Seq.iter (fun item -> log.LogInformation item.Id)

                OkObjectResult("Hello")

我尝试在 function.json 文件中指定绑定(bind)，但无论添加什么内容，bin/HttpTrigger/function.json 中的文件仅包含 HttpTrigger(C# 和 F#):

{
  "generatedBy": "Microsoft.NET.Sdk.Functions-3.0.1",
  "configurationSource": "attributes",
  "bindings": [
    {
      "type": "httpTrigger",
      "methods": [
        "get"
      ],
      "authLevel": "anonymous",
      "name": "req"
    }
  ],
  "disabled": false,
  "scriptFile": "../bin/Customer.dll",
  "entryPoint": "Customer.CosmosBindings.Run"
}

C# 和 F# 的依赖项和函数版本相同:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.CosmosDB" Version="3.0.3" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.1" />
  </ItemGroup>
  <ItemGroup>
    <Compile Include="GetCustomer.fs" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

运行 F# 示例时出现的错误:

[2/19/2020 4:01:52 PM] Starting JobHost
[2/19/2020 4:01:52 PM] Starting Host (HostId=havardandaestensenvippsnosmacboo, InstanceId=faf11b1c-b81d-49d2-8876-e4ef8785dc9f, Version=3.0.13107, ProcessId=30665, AppDomainId=1, InDebugMode=False, InDiagnosticMode=False, FunctionsExtensionVersion=(null))
[2/19/2020 4:01:52 PM] Loading functions metadata
[2/19/2020 4:01:52 PM] 1 functions loaded
[2/19/2020 4:01:52 PM] Generating 1 job function(s)
[2/19/2020 4:01:52 PM] Microsoft.Azure.WebJobs.Host: Error indexing method 'HttpTrigger'. Microsoft.Azure.WebJobs.Host: Cannot bind parameter 'toDoItems' to type IEnumerable`1. Make sure the parameter Type is supported by the binding. If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).
[2/19/2020 4:01:52 PM] Error indexing method 'HttpTrigger'
[2/19/2020 4:01:52 PM] Microsoft.Azure.WebJobs.Host: Error indexing method 'HttpTrigger'. Microsoft.Azure.WebJobs.Host: Cannot bind parameter 'toDoItems' to type IEnumerable`1. Make sure the parameter Type is supported by the binding. If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).
[2/19/2020 4:01:52 PM] Function 'HttpTrigger' failed indexing and will be disabled.
[2/19/2020 4:01:52 PM] No job functions found. Try making your job classes and methods public. If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).
[2/19/2020 4:01:52 PM] Initializing function HTTP routes
[2/19/2020 4:01:52 PM] Mapped function route 'api/HttpTrigger' [get] to 'HttpTrigger'
[2/19/2020 4:01:52 PM]
[2/19/2020 4:01:52 PM] Host initialized (199ms)
[2/19/2020 4:01:52 PM] Host started (206ms)
[2/19/2020 4:01:52 PM] Job host started
[2/19/2020 4:01:52 PM] The 'HttpTrigger' function is in error: Microsoft.Azure.WebJobs.Host: Error indexing method 'HttpTrigger'. Microsoft.Azure.WebJobs.Host: Cannot bind parameter 'toDoItems' to type IEnumerable`1. Make sure the parameter Type is supported by the binding. If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).

从 F# 代码中删除类型并仅从 CosmosDB 返回 toDoItems 也会导致错误。

[2/19/2020 4:22:33 PM] Generating 1 job function(s)
[2/19/2020 4:22:33 PM] No job functions found. Try making your job classes and methods public. If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).
[2/19/2020 4:22:33 PM] Initializing function HTTP routes

Answer 1

关于 F# 和绑定(bind)的文档不多，但基于此:https://learn.microsoft.com/azure/azure-functions/functions-reference-fsharp#binding-to-arguments ，看起来输出变量使用 byref<>对于输入变量，类型需要用 [<CLIMutable>] 修饰.

在这种情况下，作为 C# 中的 IEnumerable 我不确定是否 Seq.cast需要而不是 seq 。