[release/10.0] Multi-target Microsoft.EntityFrameworkCore.Tools for net8.0, net9.0, net10.0

[AndriySvyryd]

Fixes #38107

Description
The Microsoft.EntityFrameworkCore.Tools nuspec had a single dependency group for net8.0 with Microsoft.EntityFrameworkCore.Design >= 8.0.0. When a user's project targets net10.0, NuGet selects this group and resolves to a Design version that may be incompatible with the user's other EF Core packages. This causes a MissingMethodException for AbstractionsStrings.ArgumentIsEmpty(System.Object) because the method signature changed between major versions.

The fix adds per-TFM dependency groups (net8.0, net9.0, net10.0) so the correct major.minor version of Design is resolved based on the consumer's target framework.

Customer impact
After upgrading to Microsoft.EntityFrameworkCore.Tools 10.0.6 on an app targeting net10.0, users running Add-Migration (or other PMC commands) in Visual Studio get:

System.MissingMethodException: Method not found: 'System.String Microsoft.EntityFrameworkCore.Diagnostics.AbstractionsStrings.ArgumentIsEmpty(System.Object)'.

Workaround is to reference the appropriate version of Microsoft.EntityFrameworkCore.Design directly.

How found
More than 10 users reports on 10.0.6.

Regression
Yes, regression from 10.0.5. Introduced in #37731.

Testing
Tested manually.

Risk
Low. The change only affects the nuspec.

[Copilot]

Pull request overview

Adjusts the Microsoft.EntityFrameworkCore.Tools NuGet package metadata so NuGet resolves the correct major version of Microsoft.EntityFrameworkCore.Design based on the consuming project’s target framework (avoiding runtime MissingMethodException when installing Tools into newer TFMs).

Changes:

• Split the single dependency group into per-TFM dependency groups (net8.0, net9.0, net10.0) with matching minimum Microsoft.EntityFrameworkCore.Design versions.
• Add lib/net9.0/_._ and lib/net10.0/_._ marker files so the package advertises compatibility with those TFMs.

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

File	Description
src/EFCore.Tools/EFCore.Tools.nuspec	Adds per-TFM dependency groups to ensure the right Design major is selected for each target framework.
src/EFCore.Tools/lib/net9.0/.	Marker file to include/declare net9.0 lib folder in the nupkg.
src/EFCore.Tools/lib/net10.0/.	Marker file to include/declare net10.0 lib folder in the nupkg.

[artl93]

Regression, customer reported, approved.
How have we not hit this previously? Is this something we need to remember to do when we update 11 to make sure we are able to pick up 10 as well?

[AndriySvyryd]

How have we not hit this previously? Is this something we need to remember to do when we update 11 to make sure we are able to pick up 10 as well?

Before 10 we supported the previous LTS TFM in our tools and referenced the latest .Design package that also supported it. In 10 we decided to only support the current TFM for our packages, but still support the previous TFMs in tools, that's why we ended up with this discrepancy.

Going forward, starting with 11, the .Tools package won't bring in the .Design package at all as it was intentionally designed to not be coupled to a particular version and the dependency was there just to save users the trouble of adding it themselves. See https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-11.0/breaking-changes#ef-tools-no-design-dep