NuGetV2: Specifying an AppVeyor NuGet feed doesn't work

[KirillOsenkov]

Environment

• Server - Azure Pipelines
  https://cloudbuild.visualstudio.com/CodexIngest/_build?definitionId=123

• Agent - Hosted or Private:
  Hosted VS2017

Issue Description

Restoring via this NuGet.config file fails:
https://github.com/icsharpcode/ILSpy/blob/master/NuGet.config

Task logs

2018-11-20T01:29:18.8455315Z ##[error]The nuget command failed with exit code(1) and error(NU1101: Unable to find package Mono.Cecil. No packages exist with this id in source(s): ILSpy
NU1101: Unable to find package DiffLib. No packages exist with this id in source(s): ILSpy
NU1101: Unable to find package Microsoft.CodeAnalysis.VisualBasic. No packages exist with this id in source(s): ILSpy

[KirillOsenkov]

See related: #8850

[KirillOsenkov]

@chrisrpatterson @bryanmacfarlane hey folks, there are quite a few issues with the NuGetV2 restore task and I haven't seen any activity for months. I would like to make sure this is prioritized if possible as it's blocking real world adoption of Azure Pipelines. See related:

#7616

[KirillOsenkov]

Also I'm confused because there's NuGet and NuGetRestore and NuGetCommand and I only see NuGet in the marketplace, but the source code doesn't match. Who would be the best person I can contact internally to help me sort this out?

[KirillOsenkov]

I'm also seeing this while trying to create a CI build for https://github.com/Microsoft/TestFX. Very easy repro.

I guess the problem is that the task saves the NuGet.config into a temp file:
-ConfigFile D:\a\1\Nuget\tempNuGet_55016.config instead of using the original file in the repo.

[phil-hodgson]

@KirillOsenkov The restore is failing because the source NuGet.Config file only contains a single source (https://ci.appveyor.com/nuget/ilspy-masterfeed). It does not contain nuget.org as a source, which is where the majority of the referenced packages exist.

Whilst nuget.org may be set in a machine or user default NuGet.config file, or whilst earlier versions of nuget.exe will automatically add it, you shouldn't rely on it automatically being there.

Two options:

1. Have the repo owner add nuget.org's endpoint as a source in their NuGet.Config file
2. In your build, add a step before the restore which runs nuget sources Add -Name nuget.org -Source https://api.nuget.org/v3/index.json -ConfigFile NuGet.config