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Add a backwards-compatibility system for GDExtension method

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This adds a way to ensure that methods that were modified in the Godot API will continue working in older builds of GDExtension even if the new signature is different.

```C++
// New version (changed)
ClassDB::bind_method(D_METHOD("add_sphere","radius","position"),&MyShapes::add_sphere);
// Compatibility version (still available to extensions).
ClassDB::bind_compatibility_method(D_METHOD("add_sphere","radius"),&MyShapes::_compat_add_sphere);
```

**Q**: If I add an extra argument and provide a default value (hence can still be called the same), do I still have to provide the compatibility version?
**A**: Yes, you must still provide a compatibility method. Most language bindings use the raw method pointer to do the call and process the default parameters in the binding language, hence if the actual method signature changes it will no longer work.

**Q**: If I removed a method, can I still bind a compatibility version even though the main method no longer exists?
**A**: Yes, for methods that were removed or renamed, compatibility versions can still be provided.

**Q**: Would it be possible to automate checking that methods were removed by mistake?
**A**: Yes, as part of a future PR, the idea is to add a a command line option to Godot that can be run like : `$ godot --test-api-compatibility older_api_dump.json`, which will also be integrated to the CI runs.
This commit is contained in:
Juan Linietsky
2023-04-25 20:53:07 +02:00
parent 45cd5dcad3
commit d8078d3f4c
6 changed files with 490 additions and 32 deletions
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7
core/extension/gdextension_interface.cpp
View File

@ -984,7 +984,12 @@ static GDExtensionScriptInstancePtr gdextension_script_instance_create(const GDE
static GDExtensionMethodBindPtr gdextension_classdb_get_method_bind(GDExtensionConstStringNamePtr p_classname, GDExtensionConstStringNamePtr p_methodname, GDExtensionInt p_hash) {
const StringName classname = *reinterpret_cast<const StringName *>(p_classname);
const StringName methodname = *reinterpret_cast<const StringName *>(p_methodname);
MethodBind *mb = ClassDB::get_method(classname, methodname);
bool exists = false;
MethodBind *mb = ClassDB::get_method_with_compatibility(classname, methodname, p_hash, &exists);
if (!mb && exists) {
ERR_PRINT("Method '" + classname + "." + methodname + "' has changed and no compatibility fallback has been provided. Please open an issue.");
return nullptr;
}
ERR_FAIL_COND_V(!mb, nullptr);
if (mb->get_hash() != p_hash) {
ERR_PRINT("Hash mismatch for method '" + classname + "." + methodname + "'.");