fix(ext/ffi): allow opting out of fast ffi calls (#15131)

cli/dts/lib.deno.unstable.d.ts

@@ -430,6 +430,8 @@ declare namespace Deno {
     result: Result;
     /** When true, function calls will run on a dedicated blocking thread and will return a Promise resolving to the `result`. */
     nonblocking?: NonBlocking;
+    /** When true, function calls can safely callback into JS or trigger a GC event. Default is `false`. */
+    callback?: boolean;
   }
 
   export interface ForeignStatic<Type extends NativeType = NativeType> {

ext/ffi/lib.rs

@@ -72,6 +72,7 @@ struct Symbol {
   ptr: libffi::middle::CodePtr,
   parameter_types: Vec<NativeType>,
   result_type: NativeType,
+  can_callback: bool,
 }
 
 #[allow(clippy::non_send_fields_in_send_ty)]
@@ -433,6 +434,13 @@ struct ForeignFunction {
   result: NativeType,
   #[serde(rename = "nonblocking")]
   non_blocking: Option<bool>,
+  #[serde(rename = "callback")]
+  #[serde(default = "default_callback")]
+  callback: bool,
+}
+
+fn default_callback() -> bool {
+  false
 }
 
 // ForeignStatic's name and type fields are read and used by
@@ -599,6 +607,7 @@ where
           ptr,
           parameter_types: foreign_fn.parameters,
           result_type: foreign_fn.result,
+          can_callback: foreign_fn.callback,
         });
 
         resource.symbols.insert(symbol_key, sym.clone());
@@ -689,7 +698,8 @@ fn make_sync_fn<'s>(
 ) -> v8::Local<'s, v8::Function> {
   let mut fast_ffi_templ = None;
 
-  if !sym.parameter_types.iter().any(|t| !is_fast_api(*t))
+  if !sym.can_callback
+    && !sym.parameter_types.iter().any(|t| !is_fast_api(*t))
     && is_fast_api(sym.result_type)
   {
     let mut args = sym
@@ -941,6 +951,7 @@ where
     result_type,
     cif,
     ptr: fun_ptr,
+    ..
   } = symbol;
   let mut ffi_args: Vec<NativeValue> =
     Vec::with_capacity(parameter_types.len());
@@ -1814,6 +1825,7 @@ fn op_ffi_call_nonblocking<'scope>(
       ptr,
       parameter_types,
       result_type,
+      ..
     } = symbol.clone();
     ffi_call(call_args, &cif, ptr, &parameter_types, result_type)
   });

test_ffi/tests/ffi_types.ts

@@ -5,7 +5,7 @@
 const remote = Deno.dlopen(
   "dummy_lib.so",
   {
-    method1: { parameters: ["usize", "usize"], result: "void" },
+    method1: { parameters: ["usize", "usize"], result: "void", callback: true },
     method2: { parameters: [], result: "void" },
     method3: { parameters: ["usize"], result: "void" },
     method4: { parameters: ["isize"], result: "void" },

test_ffi/tests/test.js

@@ -164,10 +164,12 @@ const dylib = Deno.dlopen(libPath, {
   call_stored_function: {
     parameters: [],
     result: "void",
+    callback: true,
   },
   call_stored_function_2: {
     parameters: ["u8"],
     result: "void",
+    callback: true,
   },
   // Statics
   "static_u32": {
@@ -372,12 +374,14 @@ assertThrows(
   "hi",
 );
 
+const { call_stored_function } = dylib.symbols;
+
 dylib.symbols.call_fn_ptr(ptr(logCallback));
 dylib.symbols.call_fn_ptr_many_parameters(ptr(logManyParametersCallback));
 dylib.symbols.call_fn_ptr_return_u8(ptr(returnU8Callback));
 dylib.symbols.call_fn_ptr_return_buffer(ptr(returnBufferCallback));
 dylib.symbols.store_function(ptr(logCallback));
-dylib.symbols.call_stored_function();
+call_stored_function();
 dylib.symbols.store_function_2(ptr(add10Callback));
 dylib.symbols.call_stored_function_2(20);