Non-nullable result types for ToString, Find and FindAsync methods

[mjolnerbkl]

This is probably not a bug, but I am upgrading my tt-files from v3.6.0 to v3.12.0 and for some reason several generated methods are now returning non-nullable return types, which breaks my code. Any clue to what I should do to get nullable return types again?

Examples:

        string? ToString();

        TEntity? Find<TEntity>(params object[] keyValues) where TEntity : class;
        ValueTask<TEntity?> FindAsync<TEntity>(object[] keyValues, CancellationToken cancellationToken) where TEntity : class;
        ValueTask<TEntity?> FindAsync<TEntity>(params object[] keyValues) where TEntity : class;
        ValueTask<object?> FindAsync(Type entityType, object[] keyValues, CancellationToken cancellationToken);
        ValueTask<object?> FindAsync(Type entityType, params object[] keyValues);
        object? Find(Type entityType, params object[] keyValues);

...becomes

        string ToString();

        TEntity Find<TEntity>(params object[] keyValues) where TEntity : class;
        ValueTask<TEntity> FindAsync<TEntity>(object[] keyValues, CancellationToken cancellationToken) where TEntity : class;
        ValueTask<TEntity> FindAsync<TEntity>(params object[] keyValues) where TEntity : class;
        ValueTask<object> FindAsync(Type entityType, object[] keyValues, CancellationToken cancellationToken);
        ValueTask<object> FindAsync(Type entityType, params object[] keyValues);
        object Find(Type entityType, params object[] keyValues);

[sjh37]

The non-nullable signatures are from the EF6 template (TemplateEf6). The nullable ? versions - string? ToString(), TEntity? Find<TEntity>, ValueTask<TEntity?> FindAsync<TEntity> etc. - are in the EF Core template (TemplateEfCore8).

When upgrading from v3.6.0 to v3.12.0, the TemplateType enum values were renamed/extended (now EfCore8, EfCore9, EfCore10 instead of a generic EfCore). You likely still have your Database.tt set to TemplateType.Ef6, or copied the new template without updating that setting.

Fix in Database.tt: Set the correct template type for their EF Core version:

Settings.TemplateType = TemplateType.EfCore8;   // for EF Core 8
// or
Settings.TemplateType = TemplateType.EfCore9;   // for EF Core 9
// or
Settings.TemplateType = TemplateType.EfCore10;  // for EF Core 10

Also set the generator type:

Settings.GeneratorType = GeneratorType.EfCore;

Optionally, if you want #nullable enable added to the top of each generated file (needed if the project doesn't have <Nullable>enable</Nullable> in the .csproj):

Settings.AllowNullStrings = true;

There are three nullable-related settings in total:

NullableShortHand (default true) Controls whether nullable value types use T? shorthand or Nullable<T> long form. Not relevant to this issue.

AllowNullStrings (default false)

• Makes string columns generate as string?
• Adds #nullable enable to the top of every generated file
• Also makes nullable string stored procedure parameters use ? annotations

NullableReverseNavigationProperties (default false)

• This makes the reverse navigation property on one-to-one relationships nullable: MyEntity? instead of MyEntity
• Also triggers #nullable enable being added to generated files

Both AllowNullStrings and NullableReverseNavigationProperties feed into NeedsNullForgiving() (Settings.cs), which controls whether #nullable enable is emitted in the file header and whether null! forgiving operators are used on non-nullable reference properties.

So the full nullable picture to give the issue reporter is:

Setting	Purpose
TemplateType = TemplateType.EfCore8/9/10	Required for nullable Find/FindAsync/ToString
AllowNullStrings = true	string? properties + #nullable enable in files
NullableReverseNavigationProperties = true	Nullable one-to-one reverse nav props + #nullable enable in files

[sjh37]

Let me know if I can help further. If this solves your issues, please close this issue :-)