Feature request: improved hook support

Description

The past weeks I have been trying to implement several features of our existing API using JsonApiDotNetCore. Starting out with custom services and repositories, I am now trying to make more use of hooks. One thing that I’m stuck at is the hook support for reading lists.

Consider the next method in DefaultResourceService:

public virtual async Task<IEnumerable<TResource>> GetAsync()
{
    _hookExecutor?.BeforeRead<TResource>(ResourcePipeline.Get);

    var entityQuery = _repository.Get();
    entityQuery = ApplyFilter(entityQuery);
    entityQuery = ApplySort(entityQuery);
    entityQuery = ApplyInclude(entityQuery);
    entityQuery = ApplySelect(entityQuery);

    if (!IsNull(_hookExecutor, entityQuery))
    {
        var entities = await _repository.ToListAsync(entityQuery);
        _hookExecutor.AfterRead(entities, ResourcePipeline.Get);
        entityQuery = _hookExecutor.OnReturn(entities, ResourcePipeline.Get).AsQueryable();
    }

    if (_options.IncludeTotalRecordCount)
        _pageManager.TotalRecords = await _repository.CountAsync(entityQuery);

    // pagination should be done last since it will execute the query
    var pagedEntities = await ApplyPageQueryAsync(entityQuery);
    return pagedEntities;
}

The first thing to notice is that whenever you start to use a hook (OnReturn in my case), paging no longer works server-side. This is unacceptable for large tables. I think that if the hook subscriber really needs the query executed, it should do so itself and live with the consequences.

Something else I found is that hooks cannot be generic. It’s unclear to me if that is a bug or by design. To illustrate, the following works:

services.AddScoped<ResourceDefinition<Video>, VideoResourceHookContainer>();

public class VideoResourceHookContainer : TypeEmbeddedIdResourceHookContainer<Video> { }

public class TypeEmbeddedIdResourceHookContainer<TResource> 
  : ResourceDefinition<TResource> 
  where TResource : class, IIdentifiable<long> 
{
  // ...
}

but the following does not:

services.AddScoped<ResourceDefinition<Video>, TypeEmbeddedIdResourceHookContainer<Video>>();

public class TypeEmbeddedIdResourceHookContainer<TResource> 
  : ResourceDefinition<TResource> 
  where TResource : class, IIdentifiable<long> 
{
  // ...
}

Finally, the documentation on the interfaces in IResourceHookExecutor.cs is wrong. For example, IReadHookExecutor contains: “Wrapper interface for all Before execution methods.” Also the file contains the misspelling “appropiate” multiple times.

Environment

Latest commit in develop branch.

[mjartz]

Hi All, Yes i totally agree with Bart above. I’m working on a POC using JADNC 3.1.0 and have just started migrating it to the latest 4.0.0 alpha. Basic gets were working fine with paging out of the box as I had set the options.EnableResourceHooks to false. Without doing anything other than changing that option to true, all of a sudden a number of gets on large tables were trying to retrieve every record because of the queryable being enumerated to a list in the GetAsync method Bart highlighted above. I can see this potentially causing issues for a lot of people, especially as it seems hooks will need to be enabled and used in a lot of scenarios. As it stands right now, I cannot use this package with hooks enabled, without implementing a custom resource service overriding this method and using this for all of my entities. FYI, I totally understand the rationale for doing it this way in order to satisfy paging functionality after a hook may have further filtered or sorted the data, but I think this responsibility must be taken on by the developer themselves within the hook, though I acknowledge your concerns around this as well. I also like the idea of having hooks more granular so that the above would only occur if hooks were enabled, AND the OnReturn hook was actually implemented. Regard,

[bart-degreed]

Closing this in favor of #934, which proposes a simpler, non-recursive design. Combined with recently added IResourceDefinition callbacks such as OnApplyFilter, OnApplyIncludes, OnApplySparseFieldSet etc. I suspect it covers the major use cases.