Add return_exceptions argument to modal.FunctionCall.gather.

modal/_functions.py

@@ -1760,13 +1760,15 @@ async def from_id(function_call_id: str, client: Optional[_Client] = None) -> "_
         return fc
 
     @staticmethod
-    async def gather(*function_calls: "_FunctionCall[T]") -> typing.Sequence[T]:
-        """Wait until all Modal FunctionCall objects have results before returning.
+    async def gather(
+        *function_calls: "_FunctionCall[T]",
+        return_exceptions: bool = False,  # propagate exceptions (False) or aggregate them in the results list (True)
+    ) -> typing.Sequence[T | BaseException]:
+        """Returns a list of results from a variable number of Modal `FunctionCall` objects (as returned by
+        `Function.spawn()`).
 
-        Accepts a variable number of `FunctionCall` objects, as returned by `Function.spawn()`.
-
-        Returns a list of results from each FunctionCall, or raises an exception
-        from the first failing function call.
+        By default, this will raise an exception from the first failing function call. If `return_exceptions=True`, it
+        will instead aggregate exceptions in the results list.
 
         Examples:
 
@@ -1779,6 +1781,9 @@ async def gather(*function_calls: "_FunctionCall[T]") -> typing.Sequence[T]:
 
         *Added in v0.73.69*: This method replaces the deprecated `modal.functions.gather` function.
         """
+        if return_exceptions:
+            return await asyncio.gather(*[fc.get() for fc in function_calls], return_exceptions=True)
+
         try:
             return await TaskContext.gather(*[fc.get() for fc in function_calls])
         except Exception as exc:

test/function_test.py

@@ -496,6 +496,24 @@ def test_function_exception(client, servicer):
         assert "foo!" in str(excinfo.value)
 
 
+def test_function_exception_gather(client, servicer):
+    app = App()
+
+    servicer.function_body(failure)
+    failure_modal = app.function()(failure)
+    with app.run(client=client):
+        with pytest.raises(CustomException) as excinfo:
+            FunctionCall.gather(failure_modal.spawn(), failure_modal.spawn())
+        assert "foo!" in str(excinfo.value)
+
+    with app.run(client=client):
+        results = FunctionCall.gather(failure_modal.spawn(), failure_modal.spawn(), return_exceptions=True)
+        for result in results:
+            assert isinstance(result, UserCodeException)
+            assert isinstance(result.exc, CustomException)
+            assert "foo!" in str(result)
+
+
 @pytest.mark.asyncio
 async def test_function_exception_async(client, servicer):
     app = App()