ReadItemAsync does not throw exception as in documentation

Describe the bug The MS docs state that when ReadItemAsync is ran on an entity that does not exist, a 404 exception should be returned. Link to MS docs.

In my testing, no exception is thrown but the CosmosItemResponse<T> is returned with an Resource = null and a StatusCode = 404.

To Reproduce Have Cosmos SQL API Collection named tweets with partitionKey /subjectId.

using Microsoft.Azure.Cosmos;
using cosmos.test.Models;
using Xunit;

namespace cosmos.test
{
    public class CosmosTest
    {
        private const string _endpoint = "{endpoint}";
        private const string _authkey = "{authkey}";
        private const string _database = "{database}";

       [Fact]
        public async void ReadFail()
        {
            var client = new CosmosClient(_endpoint, _authkey);

            await Assert.ThrowsAsync<CosmosException>(async () =>
            {
                await client.Databases[_database].Containers["tweets"].Items.ReadItemAsync<Tweet>("foo", "not-a-real-id");
            });
        }
    }
}

Expected behavior An exception of type CosmosException with StatusCode = 404 should be thrown.

Actual behavior No exception is thrown.

Environment summary SDK Version: 3.0.0.9-preview OS Version (e.g. Windows, Linux, MacOSX) MacOSX

Additional context

$ dotnet test
Build started, please wait...
Build completed.

Test run for /Users/mpalumbo7/Code/tweet-api/test/cosmost.test/bin/Debug/netcoreapp2.2/tweet.api.test.dll(.NETCoreApp,Version=v2.2)
Microsoft (R) Test Execution Command Line Tool Version 15.9.0
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
[xUnit.net 00:00:06.0785620]     cosmos.test.CosmosTest.ReadFail [FAIL]
Failed   cosmos.test.CosmosTest.ReadFail
Error Message:
 Assert.Throws() Failure
Expected: typeof(Microsoft.Azure.Cosmos.CosmosException)
Actual:   (No exception was thrown)
Stack Trace:
   at cosmos.test.CosmosTest.ReadFail() in /Users/mpalumbo7/Code/tweet-api/test/cosmos.test/CosmosTest.cs:line 20

Total tests: 1. Passed: 0. Failed: 1. Skipped: 0.
Test Run Failed.
Test execution time: 6.7763 Seconds

[nahk-ivanov]

@j82w can we have this as an option in RequestOptions or a separate flag? Performance is a concern and to use stream APIs we need to pass serializer everywhere. It would probably improve ever so slightly if CosmosClient.ClientOptions.Serializer would be set to a default one, rather than kept null, if nothing specified, but having it in RequestOption will allow us to reuse it for all of the read APIs, not just the document.

[claitonlovato]

Hi @j82w , I am facing the opposite problem here, I am using 3.1.1 (downgraded to 3.0.0 with same results), and ReadItemAsync actually throws an exception instead of returning a ItemResponse as described on the sample documentation. Any ideas? Thank you so much. Claiton