ReadOnly properties are currently not allowed because the generated code
needs to set them, this also apply to `init` properties because they
need to be set after initialization.
This was a regression from 17b2838f39.
`MarshalUtils` was changed in the source generators to use
`ConvertTo<T>` and `CreateFrom<T>`, which don't support `GodotObject[]`
because it would need reflection.
As such, we need to keep the custom cases for `GodotObject[]` in
`MarshalUtils`.
This change aims to reduce the number of places that need to be changed
when adding or editing a Godot type to the bindings.
Since the addition of `Variant.From<T>/As<T>` and
`VariantUtils.CreateFrom<T>/ConvertTo<T>`, we can now replace a lot of
the previous code in the bindings generator and the source generators
that specify these conversions for each type manually.
The only exceptions are the generic Godot collections (`Array<T>` and
`Dictionary<TKey, TValue>`) which still use the old version, as that
one cannot be matched by our new conversion methods (limitation in the
language with generics, forcing us to use delegate pointers).
The cleanup applies to:
- Bindings generator:
- `TypeInterface.cs_variant_to_managed`
- `TypeInterface.cs_managed_to_variant`
- Source generators:
- `MarshalUtils.AppendNativeVariantToManagedExpr`
- `MarshalUtils.AppendManagedToNativeVariantExpr`
- `MarshalUtils.AppendVariantToManagedExpr`
- `MarshalUtils.AppendManagedToVariantExpr`
This commit replaces most usages of `ConvertManagedObjectToVariant` and
`ConvertVariantToManagedObjectOfType`, by using the `Godot.Variant`
struct instead of `System.Object`.
The most notable change is to the `GetGodotPropertyDefaultValues` method
that's generated for scripts. The dictionary it returns now stores
`Godot.Variant` values.
Remaining usages are:
- The `DelegateUtils` class, for the serialization of closure display
classes during assembly reloading by the editor. These display classes
are compiler generated classes to store values captured by a closure.
Since it's generated by the compiler, the only way we have to access
the fields is through reflection. This leads to using `System.Object`.
- Converting parameters when invoking constructors from the engine.
This will be replaced with source generators in the future.
- Legacy support for old `GetGodotPropertyDefaultValues` return values.
We need to keep supporting the old version of this generated method
for some time. Otherwise, if loading a project built with the previous
version, it could lead to the loss of exported property values.
Ideally, we should remove this legacy support before a stable release.
We aim to make the C# API reflection-free, mainly for concerns about
performance, and to be able to target NativeAOT in refletion-free mode,
which reduces the binary size.
One of the main usages of reflection still left was the dynamic
invokation of callable delegates, and for some time I wasn't sure
I would find an alternative solution that I'd be happy with.
The new solution uses trampoline functions to invoke the delegates:
```
static void Trampoline(object delegateObj, NativeVariantPtrArgs args, out godot_variant ret)
{
if (args.Count != 1)
throw new ArgumentException($"Callable expected 1 arguments but received {args.Count}.");
string res = ((Func<int, string>)delegateObj)(
VariantConversionCallbacks.GetToManagedCallback<int>()(args[0])
);
ret = VariantConversionCallbacks.GetToVariantCallback<string>()(res);
}
Callable.CreateWithUnsafeTrampoline((int num) => "Foo" + num, &Trampoline);
```
Of course, this is too much boilerplate for user code. To improve this,
the `Callable.From` methods were added. These are overloads that take
`Action` and `Func` delegates, which covers the most common use cases:
lambdas and method groups:
```
// Lambda
Callable.From((int num) => "Foo" + num);
// Method group
string AppendNum(int num) => "Foo" + num;
Callable.From(AppendNum);
```
Unfortunately, due to limitations in the C# language, implicit
conversions from delegates to `Callable` are not supported.
`Callable.From` does not support custom delegates. These should be
uncommon, but the Godot C# API actually uses them for event signals.
As such, the bindings generator was updated to generate trampoline
functions for event signals. It was also optimized to use `Action`
instead of a custom delegate for parameterless signals, which removes
the need for the trampoline functions for those signals.
The change to reflection-free invokation removes one of the last needs
for `ConvertVariantToManagedObjectOfType`. The only remaining usage is
from calling script constructors with parameters from the engine
(`CreateManagedForGodotObjectScriptInstance`). Once that one is made
reflection-free, `ConvertVariantToManagedObjectOfType` can be removed.
- Creates a `Godot.Offline.Config` file to configurate NuGet with
Godot's fallback folder. This is easier because now we can assume we can
override the entire file since user config will likely be in the default
`NuGet.Config` file or an additional `*.config` file.
- Ensure the NuGet fallback folder is created at the same time it is
added to the NuGet configuration so future builds don't fail.
- Add `GodotSharp` and `GodotSharpEditor` packages to the fallback folder.
- Add `.nupkg.metadata` file to packages in fallback folder.
- Refer to `Godot.SourceGenerators` using the specific non-floating version
since floating versions don't seem to work with fallbackPackageFolders.
When the C# bindings generator finds a type without meta assume the type
refers to the 64-bit version of the type:
- `float` is converted to `double`
- `int` is converted to `long`
- Replace `IndexOutOfRangeException` with `ArgumentOutOfRangeException`
- Replace `Exception` with a more specific exception
- Add the parameter name to argument exception
- Update documentation for methods that throw exceptions
- Use `StringBuilder` to build exception messages
- Ensure exception messages end with a period
- Remove event as a valid target of `SignalAttribute`
- Stop adding the `[Signal]` attribute to events in bindings_generator
- Make bindings_generator use the `EventHandler` suffix to be consistent with the C# source generator
- Remove obsolete comment about the signal's delegate name
- MustBeVariant attribute can be used to enforce that generic types must
be a marshable from/to Variant.
- Also renames all diagnostic ids to be valid unicode identifiers.
This new version does not support the following type arguments:
- Generic types
- Array of Godot Object (Godot.Object[]) or derived types
The new implementation uses delegate pointers to call the Variant
conversion methods. We do type checking only once in the static
constructor to get the conversion delegates.
Now, we no longer need to do type checking every time, and we no
longer have to box value types.
This is the best implementation I could come up with, as C# generics
don't support anything similar to C++ template specializations.
- Array and Dictionary now store `Variant` instead of `System.Object`.
- Removed generic Array and Dictionary.
They cause too much issues, heavily relying on reflection and
very limited by the lack of a generic specialization.
- Removed support for non-Godot collections.
Support for them also relied heavily on reflection for marshaling.
Support for them will likely be re-introduced in the future, but
it will have to rely on source generators instead of reflection.
- Reduced our use of reflection.
The remaining usages will be moved to source generators soon.
The only usage that I'm not sure yet how to replace is dynamic
invocation of delegates.
