Merge pull request #1197 from godot-rust/bugfix/hot-reload-noinit

Make hot-reload work with `#[class(no_init)]`

Author: Bromeon

.github/workflows/full-ci.yml

@@ -246,7 +246,7 @@ jobs:
             os: macos-13
             artifact-name: macos-x86-nightly
             godot-binary: godot.macos.editor.dev.x86_64
-            with-hot-reload: true
+            hot-reload: stable
 
           - name: macos-double-x86
             os: macos-13
@@ -264,7 +264,7 @@ jobs:
             os: macos-latest
             artifact-name: macos-arm-nightly
             godot-binary: godot.macos.editor.dev.arm64
-            with-hot-reload: true
+            hot-reload: stable
 
            # api-custom on macOS arm64 not working, due to clang linker issues.
 #          - name: macos-double-arm
@@ -285,7 +285,7 @@ jobs:
             os: windows-latest
             artifact-name: windows-nightly
             godot-binary: godot.windows.editor.dev.x86_64.exe
-            with-hot-reload: true
+            hot-reload: stable
 
           - name: windows-double
             os: windows-latest
@@ -317,7 +317,7 @@ jobs:
             artifact-name: linux-nightly
             godot-binary: godot.linuxbsd.editor.dev.x86_64
             rust-extra-args: --features itest/codegen-full
-            with-hot-reload: true
+            hot-reload: api-custom
 
           # Combines now a lot of features, but should be OK. lazy-function-tables doesn't work with experimental-threads.
           - name: linux-double-lazy
@@ -352,12 +352,14 @@ jobs:
             rust-cache-key: release
 
           # Linux compat (4.1 disabled, already covered by memcheck)
+          # No hot-reload before 4.4, as the Godot project is 4.4+.
 
           - name: linux-4.4
             os: ubuntu-22.04
             artifact-name: linux-4.4
             godot-binary: godot.linuxbsd.editor.dev.x86_64
             godot-prebuilt-patch: '4.4'
+            hot-reload: stable
 
           - name: linux-4.3
             os: ubuntu-22.04
@@ -418,10 +420,11 @@ jobs:
           godot-indirect-json: ${{ matrix.godot-indirect-json }}
 
       - name: "Build and test hot-reload"
-        if: ${{ matrix.with-hot-reload }}
+        if: ${{ matrix.hot-reload }}
         working-directory: itest/hot-reload/godot
         # Repeat a few times, our hot reload integration test can sometimes be a bit flaky.
-        run: $RETRY ./run-test.sh
+        # Don't pass in rust-extra-args as environment; they're intended for itest.
+        run: $RETRY ./run-test.sh ${{ matrix.hot-reload }}
         shell: bash
 
 

.github/workflows/minimal-ci.yml

@@ -159,7 +159,7 @@ jobs:
             artifact-name: linux-nightly
             godot-binary: godot.linuxbsd.editor.dev.x86_64
             rust-extra-args: --features itest/codegen-full
-            with-hot-reload: true
+            hot-reload: stable
 
           - name: linux-custom-api-json
             os: ubuntu-22.04
@@ -173,6 +173,7 @@ jobs:
             artifact-name: linux-nightly
             godot-binary: godot.linuxbsd.editor.dev.x86_64
             rust-extra-args: --features itest/experimental-threads,itest/codegen-full-experimental,godot/api-custom,godot/serde,itest/register-docs
+            hot-reload: api-custom
 
           - name: linux-release
             os: ubuntu-22.04
@@ -240,9 +241,9 @@ jobs:
           godot-indirect-json: ${{ matrix.godot-indirect-json }}
 
       - name: "Build and test hot-reload"
-        if: ${{ matrix.with-hot-reload }}
+        if: ${{ matrix.hot-reload }}
         working-directory: itest/hot-reload/godot
-        run: ./run-test.sh
+        run: ./run-test.sh ${{ matrix.hot-reload }}
         shell: bash
 
 

godot-core/src/registry/callbacks.rs

@@ -43,6 +43,24 @@ pub unsafe extern "C" fn create<T: cap::GodotDefault>(
     create_custom(T::__godot_user_init).unwrap_or(std::ptr::null_mut())
 }
 
+/// Workaround for <https://github.com/godot-rust/gdext/issues/874> before Godot 4.5.
+///
+/// Godot expects a creator function, but doesn't require an actual object to be instantiated.
+#[cfg(all(since_api = "4.4", before_api = "4.5"))]
+pub unsafe extern "C" fn create_null<T>(
+    _class_userdata: *mut std::ffi::c_void,
+    _notify_postinitialize: sys::GDExtensionBool,
+) -> sys::GDExtensionObjectPtr {
+    std::ptr::null_mut()
+}
+
+#[cfg(before_api = "4.4")]
+pub unsafe extern "C" fn create_null<T>(
+    _class_userdata: *mut std::ffi::c_void,
+) -> sys::GDExtensionObjectPtr {
+    std::ptr::null_mut()
+}
+
 /// Godot FFI function for recreating a GDExtension instance, e.g. after a hot reload.
 ///
 /// If the `init()` constructor panics, null is returned.
@@ -55,6 +73,17 @@ pub unsafe extern "C" fn recreate<T: cap::GodotDefault>(
         .unwrap_or(std::ptr::null_mut())
 }
 
+/// Workaround for <https://github.com/godot-rust/gdext/issues/874> before Godot 4.5.
+///
+/// Godot expects a creator function, but doesn't require an actual object to be instantiated.
+#[cfg(all(since_api = "4.2", before_api = "4.5"))]
+pub unsafe extern "C" fn recreate_null<T>(
+    _class_userdata: *mut std::ffi::c_void,
+    _object: sys::GDExtensionObjectPtr,
+) -> sys::GDExtensionClassInstancePtr {
+    std::ptr::null_mut()
+}
+
 pub(crate) fn create_custom<T, F>(
     make_user_instance: F,
 ) -> Result<sys::GDExtensionObjectPtr, PanicPayload>

godot-core/src/registry/plugin.rs

@@ -147,6 +147,10 @@ pub struct Struct {
 
     /// Godot low-level `create` function, wired up to library-generated `init`.
     ///
+    /// For `#[class(no_init)]`, behavior depends on Godot version:
+    /// - 4.5 and later: `None`
+    /// - until 4.4: a dummy function that fails, to not break hot reloading.
+    ///
     /// This is mutually exclusive with [`ITraitImpl::user_create_fn`].
     pub(crate) generated_create_fn: Option<GodotCreateFn>,
 
@@ -222,6 +226,19 @@ impl Struct {
         self
     }
 
+    // Workaround for https://github.com/godot-rust/gdext/issues/874, before https://github.com/godotengine/godot/pull/99133 is merged in 4.5.
+    #[cfg(before_api = "4.5")]
+    pub fn with_generated_no_default<T: GodotClass>(mut self) -> Self {
+        set(&mut self.generated_create_fn, callbacks::create_null::<T>);
+
+        #[cfg(since_api = "4.2")]
+        set(
+            &mut self.generated_recreate_fn,
+            callbacks::recreate_null::<T>,
+        );
+        self
+    }
+
     pub fn with_default_get_virtual_fn<T: GodotClass + UserClass>(mut self) -> Self {
         set(
             &mut self.default_get_virtual_fn,

godot-macros/src/class/derive_godot_class.rs

@@ -122,6 +122,10 @@ pub fn derive_godot_class(item: venial::Item) -> ParseResult<TokenStream> {
         }
         InitStrategy::Absent => {
             is_instantiable = false;
+
+            // Workaround for https://github.com/godot-rust/gdext/issues/874 before Godot 4.5.
+            #[cfg(before_api = "4.5")]
+            modifiers.push(quote! { with_generated_no_default::<#class_name> });
         }
     };
     if is_instantiable {

itest/hot-reload/godot/run-test.sh

@@ -6,6 +6,16 @@
 
 rel="."
 
+# If argument is 'api-custom', set 'cargoArgs' to use that feature. If 'stable', set 'cargoArgs' to empty string. Otherwise, error.
+if [[ $1 == "api-custom" ]]; then
+  cargoArgs="--features godot/api-custom"
+elif [[ $1 == "stable" ]]; then
+  cargoArgs=""
+else
+  echo "[Bash]      Error: Unknown argument '$1'. Expected 'api-custom' or 'stable'."
+  exit 1
+fi
+
 # Restore un-reloaded files on exit (for local testing).
 cleanedUp=0 # avoid recursion if cleanup fails
 godotPid=0 # kill previous instance if necessary
@@ -36,7 +46,6 @@ cp editor_layout.cfg $rel/.godot/editor/editor_layout.cfg
 #cp MainScene.tscn $rel/MainScene.tscn
 
 # Compile original Rust source.
-cargoArgs=""
 #cargoArgs="--features godot/__debug-log"
 cargo build -p hot-reload $cargoArgs
 

itest/hot-reload/rust/src/lib.rs

@@ -28,6 +28,9 @@ struct Reloadable {
     #[export]
     #[init(val = Planet::Earth)]
     favorite_planet: Planet,
+
+    #[init(val = NoDefault::obtain())]
+    _other_object: Gd<NoDefault>,
 }
 
 #[godot_api]
@@ -41,10 +44,24 @@ impl Reloadable {
     fn from_string(s: GString) -> Gd<Self> {
         Gd::from_object(Reloadable {
             favorite_planet: Planet::from_godot(s),
+            _other_object: NoDefault::obtain(),
         })
     }
 }
 
+// no_init reloadability - https://github.com/godot-rust/gdext/issues/874.
+#[derive(GodotClass)]
+#[class(no_init, base=Node)]
+struct NoDefault {}
+
+#[godot_api]
+impl NoDefault {
+    #[func]
+    fn obtain() -> Gd<Self> {
+        Gd::from_object(NoDefault {})
+    }
+}
+
 // ----------------------------------------------------------------------------------------------------------------------------------------------
 
 #[derive(GodotConvert, Var, Export)]