Supporting `EF.Functions.Like` and/or prossibility to provide cusotm `ExpressionVisitor`

[InspiringCode]

Is there any chance that you can support the most common EF functions like EF.Functions.Like?

An relatively simple approach might be to write an ExpressionVisitor that replace those function calls with mock functions.

I think it would generally be a great idea to add an optional Visitor property to TestAsyncEnumerableEfCore<T> where you can pass a custom visitor that is used instead of the new TestExpressionVisitor(). This would allow developers to mock all sorts of custom functions and the like.

I would really appreciate this feature.

[ramantsitou]

Hello @InspiringCode I also think this is indeed a great idea to implement functionality to support EF.Functions.Like, but unfortunately I will not have enough time to implement it. Feel free to provide a pull request with the infrastructure and I would be happy to include it to the next release. Please don't forget to cover the case by additional tests to minimize possibility of regressions for the future. Thanks for the understanding.

[Catlandor]

Since I faced the same problem and found a temporary solution, I’m sharing the workaround here until a custom expression visitor is available:
I used FakeItEasy to mock the QueryProvider and added logic to support scenarios such as mocking EF.Functions.ILike.

public override DbSet<TEntity> Set<TEntity>()
{
    var mockDbSet = _testDataContext.GetAll<TEntity>().AsQueryable().BuildMockDbSet();

    // Configure the mock DbSet to use a custom query provider that rewrites LIKE expressions
    // to string.Contains, simulating the behavior of ILike in PostgreSQL.
    var provider = new LikeRewritingQueryProvider(((IQueryable<TEntity>)mockDbSet).Provider);
    A.CallTo(() => ((IQueryable<TEntity>)mockDbSet).Provider).Returns(provider);

    return mockDbSet;
}

LikeRewritingQueryProvider:

public class LikeRewritingQueryProvider : IAsyncQueryProvider
{
    private readonly IQueryProvider _inner;

    public LikeRewritingQueryProvider(IQueryProvider inner)
    {
        _inner = inner;
    }

    public IQueryable CreateQuery(Expression expression)
        => _inner.CreateQuery(Rewrite(expression));

    public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
        => _inner.CreateQuery<TElement>(Rewrite(expression));

    public object? Execute(Expression expression)
        => _inner.Execute(Rewrite(expression));

    public TResult Execute<TResult>(Expression expression)
        => _inner.Execute<TResult>(Rewrite(expression));

    public IAsyncEnumerable<TResult> ExecuteAsync<TResult>(Expression expression)
        => (IAsyncEnumerable<TResult>)((IAsyncQueryProvider)_inner).ExecuteAsync<TResult>(Rewrite(expression))!;

    public TResult ExecuteAsync<TResult>(Expression expression, CancellationToken cancellationToken = default)
        => ((IAsyncQueryProvider)_inner).ExecuteAsync<TResult>(Rewrite(expression), cancellationToken);

    private static Expression Rewrite(Expression expression)
    {
        var visitor = new LikeExpressionVisitor();
        return visitor.Visit(expression)!;
    }
}

LikeExpressionVisitor

[ramantsitou]

Done in v8.0.0 - Thanks @Catlandor