NSubstitute future improvements

[zvirja]

Let's collect improvements we could/should make in our next major versions and are not allowed to apply now because of SemVer. Issue might be updated.

• [ ] Make RouteAction a read-only struct to optimize performance

• [ ] Return array instead of IList, so we can optimize contract

  https://github.com/nsubstitute/NSubstitute/blob/deea0eaf8e2a193d3a1ccccd308a3a53460e786a/src/NSubstitute/Core/IThreadLocalContext.cs#L27

• [ ] Refactor ICall and replace Get methods with properties https://github.com/nsubstitute/NSubstitute/blob/a2462d5953e6099dde26d5f0a4d0045898210aa7/src/NSubstitute/Core/ICall.cs#L8-L19

• [ ] Make NSubstitute.Core.Argument a read-only struct, as it's a thin wrapper on top of ICall and index.

• [ ] Rework IAutoValueProvider interface to:

  • Have only bool TryCreateValue(Type type, out object result) method
  • Avoid cyclic dependency from provider to list of all providers
  • Expose single aggregate provider from factory rather than an array of providers.

• [ ] Make the ReflectionExtensions helper internal and remove OrNull suffix as we use nullability for that.

• [ ] Normalize Extension-like classes, as at the moment we have a plenty of them and it's a bit hard to navigate through them.

• [ ] Add class constraint to all the DSL extension methods receiving substitute. Example: ReceivedExtensions.Received()

• [ ] Review IPendingSpecification interface and potentially change it to Try pattern.

• [x] Convert to a record once we drop .NET Standard 1.3 support:

  • ArgumentMatchInfo
  • Quantity descendants

• [ ] Do not expose internal classes from Core namespace, but instead expose interfaces.

• [ ] Make SubsitutionContext constructor private, so it can be instantiated via container only.

• [ ] Change return type of ArgumentMatchInfo.DescribeNonMatch to return null if cannot describe instead of an empty string.