Merge pull request #1367 from JoeyEamigh/fix_macos_hot_reload

Fix hot-reload crashes on macOS when the `.gdextension` file changes

Author: Bromeon

godot-core/src/meta/class_id.rs

@@ -309,8 +309,20 @@ impl ClassIdCache {
     }
 
     fn clear(&mut self) {
-        self.entries.clear();
+        // MACOS-PARTIAL-RELOAD: Previous implementation for when upstream fixes `.gdextension` reload.
+        // self.entries.clear();
+        // self.type_to_index.clear();
+        // self.string_to_index.clear();
+
+        // MACOS-PARTIAL-RELOAD: Preserve existing `ClassId` entries when only the `.gdextension` reloads so indices stay valid.
+        // There are two types of hot reload: `dylib` reload (`dylib` `mtime` newer) unloads and reloads the library, whereas
+        // `.gdextension` reload (`.gdextension` `mtime` newer) re-initializes the existing `dylib` without unloading it. To handle
+        // `.gdextension` reload, keep the backing entries (and thus the `string_to_index` map) but drop cached Godot `StringNames`
+        // and the `TypeId` lookup so they can be rebuilt.
+        for entry in &mut self.entries {
+            entry.godot_str = OnceCell::new();
+        }
+
         self.type_to_index.clear();
-        self.string_to_index.clear();
     }
 }

godot-ffi/src/lib.rs

@@ -283,7 +283,15 @@ pub unsafe fn initialize(
 /// # Safety
 /// See [`initialize`].
 pub unsafe fn deinitialize() {
-    deinitialize_binding()
+    deinitialize_binding();
+
+    // MACOS-PARTIAL-RELOAD: Clear the main thread ID to allow re-initialization during hot reload.
+    #[cfg(not(wasm_nothreads))]
+    {
+        if MAIN_THREAD_ID.is_initialized() {
+            MAIN_THREAD_ID.clear();
+        }
+    }
 }
 
 fn print_preamble(version: GDExtensionGodotVersion) {

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

@@ -37,6 +37,39 @@ cleanup() {
 set -euo pipefail
 trap cleanup EXIT
 
+godotAwait() {
+  if [[ $godotPid -ne 0 ]]; then
+    echo "[Bash]      Error: godotAwait called while Godot (PID $godotPid) is still running."
+    exit 1
+  fi
+
+  $GODOT4_BIN -e --headless --path $rel &
+  godotPid=$!
+  echo "[Bash]      Wait for Godot ready (PID $godotPid)..."
+
+  $GODOT4_BIN --headless --no-header --script ReloadOrchestrator.gd -- await
+}
+
+godotNotify() {
+  if [[ $godotPid -eq 0 ]]; then
+    echo "[Bash]      Error: godotNotify called but Godot is not running."
+    exit 1
+  fi
+
+  $GODOT4_BIN --headless --no-header --script ReloadOrchestrator.gd -- notify
+
+  echo "[Bash]      Wait for Godot exit..."
+  local status=0
+  wait $godotPid
+  status=$?
+  echo "[Bash]      Godot (PID $godotPid) has completed with status $status."
+  godotPid=0
+
+  if [[ $status -ne 0 ]]; then
+    exit $status
+  fi
+}
+
 echo "[Bash]      Start hot-reload integration test..."
 
 # Restore un-reloaded file (for local testing).
@@ -54,22 +87,25 @@ cargo build -p hot-reload $cargoArgs
 # Wait briefly so artifacts are present on file system.
 sleep 0.5
 
-$GODOT4_BIN -e --headless --path $rel &
-godotPid=$!
-echo "[Bash]      Wait for Godot ready (PID $godotPid)..."
+# ----------------------------------------------------------------
+# Test Case 1: Update Rust source and compile to trigger reload.
+# ----------------------------------------------------------------
 
-$GODOT4_BIN --headless --no-header --script ReloadOrchestrator.gd -- await
-$GODOT4_BIN --headless --no-header --script ReloadOrchestrator.gd -- replace
+echo "[Bash]      Scenario 1: Reload after updating Rust source..."
 
+godotAwait
+$GODOT4_BIN --headless --no-header --script ReloadOrchestrator.gd -- replace
 # Compile updated Rust source.
 cargo build -p hot-reload $cargoArgs
+godotNotify
 
-$GODOT4_BIN --headless --no-header --script ReloadOrchestrator.gd -- notify
-
-echo "[Bash]      Wait for Godot exit..."
-wait $godotPid
-status=$?
-echo "[Bash]      Godot (PID $godotPid) has completed with status $status."
-
+# ----------------------------------------------------------------
+# Test Case 2: Touch the .gdextension file to trigger reload.
+# ----------------------------------------------------------------
 
+echo "[Bash]      Scenario 2: Reload after touching rust.gdextension..."
 
+godotAwait
+# Update timestamp to trigger reload.
+touch "$rel/rust.gdextension"
+godotNotify