jaredcnance / ef-migration-issue Goto Github PK

dotnet ef migrations remove uses the migration *.Designer.cs file to rollback state of the DbContextModelSnapshot.cs file.

This is likely to cause problems when merging changes across multiple branches.

It is not uncommon for multiple developers to work on changes on different branches and then merge those changes back into their "master" branch. An example workflow might look like:

• branch B and C get created from branch A
• branch B generates migrations at timestamp 0
• branch C generates migrations at timestamp 1, whose designer file does not contain the changes from B
• branch B gets merged into A
• branch C gets merged into A

Resolving conflicts across common files, the AppDbContextModelSnapshot and the DbContext are relatively straightforward. Additional migration files are simple because there will be no conflicts. However, the *.Designer.cs represent a potentially incorrect state of the model because they represent an isolated view of the total state, not just the migration changes. Although, the AppDbContextModelSnapshot is a view of the total state, it is centralized, not isolated and can be easily diffed and conflicts resolved.

When developers merge their branches back in, the migration designer file for the second branch has the chance of overriding the "state" created by the first branch. This repository is an example of such a condition.

To reproduce the issue, clone this repository and run: dotnet ef migrations remove.

The preivous migration 20170616182356_modelC should be removed.

No migration is removed, but the changes from 20170616182300_modelB are removed from AppDbContextModelSnapshot.

This represents a serious blocker to adopting the EF Core migrations workflow on a multi-person team.