EF Core cannot create migrations under specific conditions

[Nihlus]

Using EF Core 2.2.6 in a .NET Core 3.0 project, the dotnet ef migrations commands may fail with an unexpected exception related to not finding the appropriate version of System.ComponentModel.Annotations. The issue prevents any use of migrations via the dotnet tooling, but does not prevent migrations from running via the application itself (MigrateAsync()).

The issue is relatively rare, but an extremely annoying issue for projects with the layout that causes the problem.

In short, given the following:

• Let A1 be an assembly targeting netcoreapp2.2;netcoreapp3.0
• Let A2 be an assembly targeting netcoreapp2.2;netcoreapp3.0
• Let A1 have a ProjectReference to A2
• Let A2 have a PackageReference to Microsoft.EntityFrameworkCore.Design, 2.2.6
• Let C be a database context defined in A1
• Let E be a database entity defined in A1
• Let E have at least one public property that uses an attribute from
  System.ComponentModel.DataAnnotations

then, any dotnet ef migrations commands that run in a netcoreapp3.0 context will fail to run, producing the following error: https://gist.github.com/Nihlus/330279348697561a7002b2972ee54bbe

Commands running in a netcoreapp2.2 context succeed, and are not affected.

Steps to reproduce

An example project with minimal reproductions has been created, and is available at https://github.com/Nihlus/EFCore.Repro.

The master branch represents the project in a reproducing state, where dotnet ef commands fail. The branches repro-1 and repro-2 represent two permutations of non-reproducing states, where the required conditions for the problem are not met.

• repro-1 - removes the attribute from System.ComponentModel.DataAnnotations from the property in E
• repro-2 - references Microsoft.EntityFrameworkCore.Design, 2.2.6 directly from A1

To reproduce the issue locally, do the following:

1. Clone the above repository
2. Run dotnet build
3. Run dotnet ef migrations add Test --framework netcoreapp3.0

To see the non-reproducing permutations, check out the relevant branch and repeat from step 2.

Further technical details

EF Core version: 2.2.6
Database provider: Microsoft.EntityFrameworkCore.Sqlite 2.2.6
Operating system: Linux Mint 19.3 (Ubuntu 18.04)

Target framework: .

• .NET Core 3.0
• .NET Core 2.2

IDE:

• JetBrains Rider 2019.3.1
• No IDE

[ajcvickers]

This looks like another example of https://github.com/dotnet/corefx/issues/33643

[joperezr]

The problem here seems to be more specific to the ef migrations command which is not really developed in this repo, so I think that a better place for an issue like this would be https://github.com/dotnet/aspnetcore-tooling. Do you mind openning the issue there so that the right people get engaged and look into this?

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