Add explicit_mode to compute contexts

python_modules/dagster/dagster/_core/execution/context/compute.py

@@ -1222,6 +1222,14 @@ def asset_check_spec(self) -> AssetCheckSpec:
         )
         return asset_checks_def.spec
 
+    # In explicit mode, no conversion is done on returned values and missing but expected outputs are not
+    # allowed.
+    def is_explicit_mode(self) -> bool:
+        return self._step_execution_context.is_explicit_mode()
+
+    def set_explicit_mode(self):
+        self._step_execution_context.set_explicit_mode()
+
 
 # actually forking the object type for assets is tricky for users in the cases of:
 #  * manually constructing ops to make AssetsDefinitions

python_modules/dagster/dagster/_core/execution/context/invocation.py

@@ -447,6 +447,7 @@ def __init__(
         self._partition_key = partition_key
         self._partition_key_range = partition_key_range
         self._assets_def = assets_def
+        self._is_explicit_mode = False
 
     @property
     def op_config(self) -> Any:
@@ -714,6 +715,14 @@ def add_metadata_two_outputs(context) -> Tuple[str, int]:
         else:
             self._output_metadata[output_name] = metadata
 
+    # In explicit mode, no conversion is done on returned values and missing but expected outputs are not
+    # allowed.
+    def is_explicit_mode(self) -> bool:
+        return self._is_explicit_mode
+
+    def set_explicit_mode(self):
+        self._is_explicit_mode = True
+
 
 def build_op_context(
     resources: Optional[Mapping[str, Any]] = None,

python_modules/dagster/dagster/_core/execution/context/system.py

@@ -559,6 +559,16 @@ def __init__(
         self._is_external_input_asset_version_info_loaded = False
         self._data_version_cache: Dict[AssetKey, "DataVersion"] = {}
 
+        self._is_explicit_mode = False
+
+    # In explicit mode, no conversion is done on returned values and missing but expected outputs are not
+    # allowed.
+    def is_explicit_mode(self) -> bool:
+        return self._is_explicit_mode
+
+    def set_explicit_mode(self) -> None:
+        self._is_explicit_mode = True
+
     @property
     def step(self) -> ExecutionStep:
         return self._step

python_modules/dagster/dagster/_core/execution/plan/compute.py

@@ -27,6 +27,7 @@
     NodeHandle,
     Output,
 )
+from dagster._core.definitions.asset_check_spec import AssetCheckHandle
 from dagster._core.definitions.asset_layer import AssetLayer
 from dagster._core.definitions.op_definition import OpComputeFunction
 from dagster._core.definitions.result import MaterializeResult
@@ -203,14 +204,42 @@ def execute_core_compute(
     for step_output in _yield_compute_results(step_context, inputs, compute_fn):
         yield step_output
         if isinstance(step_output, (DynamicOutput, Output)):
-            emitted_result_names.add(step_output.output_name)
+            output_name = step_output.output_name
+        elif isinstance(step_output, MaterializeResult):
+            asset_key = (
+                step_output.asset_key
+                or step_context.job_def.asset_layer.asset_key_for_node(step_context.node_handle)
+            )
+            output_name = step_context.job_def.asset_layer.node_output_handle_for_asset(
+                asset_key
+            ).output_name
+        elif isinstance(step_output, AssetCheckEvaluation):
+            output_name = step_context.job_def.asset_layer.get_output_name_for_asset_check(
+                step_output.asset_check_handle
+            )
+        elif isinstance(step_output, AssetCheckResult):
+            if step_output.asset_key and step_output.check_name:
+                handle = AssetCheckHandle(step_output.asset_key, step_output.check_name)
+            else:
+                handle = step_output.to_asset_check_evaluation(step_context).asset_check_handle
+            output_name = step_context.job_def.asset_layer.get_output_name_for_asset_check(handle)
+        else:
+            output_name = None
+        if output_name:
+            emitted_result_names.add(output_name)
 
     expected_op_output_names = {
         output.name for output in step.step_outputs if not output.properties.asset_check_handle
     }
     omitted_outputs = expected_op_output_names.difference(emitted_result_names)
     if omitted_outputs:
-        step_context.log.info(
-            f"{step_context.op_def.node_type_str} '{step.node_handle}' did not fire "
-            f"outputs {omitted_outputs!r}"
-        )
+        if step_context.is_explicit_mode():
+            raise DagsterInvariantViolationError(
+                f"{step_context.op_def.node_type_str} '{step.node_handle}' did not yield or return "
+                f"expected outputs {omitted_outputs!r}."
+            )
+        else:
+            step_context.log.info(
+                f"{step_context.op_def.node_type_str} '{step.node_handle}' did not fire "
+                f"outputs {omitted_outputs!r}"
+            )

python_modules/dagster/dagster/_core/execution/plan/compute_generator.py

@@ -268,73 +268,87 @@ def validate_and_coerce_op_result_to_iterator(
             " return no results."
         )
     elif output_defs:
-        for position, output_def, element in _zip_and_iterate_op_result(
-            result, context, output_defs
-        ):
-            annotation = _get_annotation_for_output_position(position, context.op_def, output_defs)
-            if output_def.is_dynamic:
-                if not isinstance(element, list):
-                    raise DagsterInvariantViolationError(
-                        f"Error with output for {context.describe_op()}: "
-                        f"dynamic output '{output_def.name}' expected a list of "
-                        "DynamicOutput objects, but instead received instead an "
-                        f"object of type {type(element)}."
-                    )
-                for item in element:
-                    if not isinstance(item, DynamicOutput):
+        # Skip any return-specific validation and treat it like a generator op
+        if context.is_explicit_mode():
+            # If nothing was returned, treat it as an empty tuple instead of a `(None,)`.
+            # This is important for delivering the correct error message when an output is missing.
+            if result is None:
+                result_tuple = tuple()
+            elif not isinstance(result, tuple) or is_named_tuple_instance(result):
+                result_tuple = (result,)
+            else:
+                result_tuple = result
+            yield from result_tuple
+        else:
+            for position, output_def, element in _zip_and_iterate_op_result(
+                result, context, output_defs
+            ):
+                annotation = _get_annotation_for_output_position(
+                    position, context.op_def, output_defs
+                )
+                if output_def.is_dynamic:
+                    if not isinstance(element, list):
                         raise DagsterInvariantViolationError(
                             f"Error with output for {context.describe_op()}: "
-                            f"dynamic output '{output_def.name}' at position {position} expected a "
-                            "list of DynamicOutput objects, but received an "
-                            f"item with type {type(item)}."
+                            f"dynamic output '{output_def.name}' expected a list of "
+                            "DynamicOutput objects, but instead received instead an "
+                            f"object of type {type(element)}."
+                        )
+                    for item in element:
+                        if not isinstance(item, DynamicOutput):
+                            raise DagsterInvariantViolationError(
+                                f"Error with output for {context.describe_op()}: dynamic output"
+                                f" '{output_def.name}' at position {position} expected a list of"
+                                " DynamicOutput objects, but received an item with type"
+                                f" {type(item)}."
+                            )
+                        dynamic_output = cast(DynamicOutput, item)
+                        _check_output_object_name(dynamic_output, output_def, position)
+
+                        with disable_dagster_warnings():
+                            yield DynamicOutput(
+                                output_name=output_def.name,
+                                value=dynamic_output.value,
+                                mapping_key=dynamic_output.mapping_key,
+                                metadata=dynamic_output.metadata,
+                            )
+                elif isinstance(element, MaterializeResult):
+                    yield element  # coerced in to Output in outer iterator
+                elif isinstance(element, Output):
+                    if annotation != inspect.Parameter.empty and not is_generic_output_annotation(
+                        annotation
+                    ):
+                        raise DagsterInvariantViolationError(
+                            f"Error with output for {context.describe_op()}: received Output object"
+                            f" for output '{output_def.name}' which does not have an Output"
+                            f" annotation. Annotation has type {annotation}."
                         )
-                    dynamic_output = cast(DynamicOutput, item)
-                    _check_output_object_name(dynamic_output, output_def, position)
+                    _check_output_object_name(element, output_def, position)
 
                     with disable_dagster_warnings():
-                        yield DynamicOutput(
+                        yield Output(
                             output_name=output_def.name,
-                            value=dynamic_output.value,
-                            mapping_key=dynamic_output.mapping_key,
-                            metadata=dynamic_output.metadata,
+                            value=element.value,
+                            metadata=element.metadata,
+                            data_version=element.data_version,
                         )
-            elif isinstance(element, MaterializeResult):
-                yield element  # coerced in to Output in outer iterator
-            elif isinstance(element, Output):
-                if annotation != inspect.Parameter.empty and not is_generic_output_annotation(
-                    annotation
-                ):
-                    raise DagsterInvariantViolationError(
-                        f"Error with output for {context.describe_op()}: received Output object for"
-                        f" output '{output_def.name}' which does not have an Output annotation."
-                        f" Annotation has type {annotation}."
-                    )
-                _check_output_object_name(element, output_def, position)
-
-                with disable_dagster_warnings():
-                    yield Output(
-                        output_name=output_def.name,
-                        value=element.value,
-                        metadata=element.metadata,
-                        data_version=element.data_version,
-                    )
-            else:
-                # If annotation indicates a generic output annotation, and an
-                # output object was not received, throw an error.
-                if is_generic_output_annotation(annotation):
-                    raise DagsterInvariantViolationError(
-                        f"Error with output for {context.describe_op()}: output "
-                        f"'{output_def.name}' has generic output annotation, "
-                        "but did not receive an Output object for this output. "
-                        f"Received instead an object of type {type(element)}."
-                    )
-                if result is None and output_def.is_required is False:
-                    context.log.warning(
-                        'Value "None" returned for non-required output '
-                        f'"{output_def.name}" of {context.describe_op()}. '
-                        "This value will be passed to downstream "
-                        f"{context.op_def.node_type_str}s. For conditional "
-                        "execution, results must be yielded: "
-                        "https://docs.dagster.io/concepts/ops-jobs-graphs/graphs#with-conditional-branching"
-                    )
-                yield Output(output_name=output_def.name, value=element)
+                else:
+                    # If annotation indicates a generic output annotation, and an
+                    # output object was not received, throw an error.
+                    if is_generic_output_annotation(annotation):
+                        raise DagsterInvariantViolationError(
+                            f"Error with output for {context.describe_op()}: output "
+                            f"'{output_def.name}' has generic output annotation, "
+                            "but did not receive an Output object for this output. "
+                            f"Received instead an object of type {type(element)}."
+                        )
+                    if result is None and output_def.is_required is False:
+                        context.log.warning(
+                            'Value "None" returned for non-required output '
+                            f'"{output_def.name}" of {context.describe_op()}. '
+                            "This value will be passed to downstream "
+                            f"{context.op_def.node_type_str}s. For conditional "
+                            "execution, results must be yielded: "
+                            "https://docs.dagster.io/concepts/ops-jobs-graphs/graphs#with-conditional-branching"
+                        )
+                    yield Output(output_name=output_def.name, value=element)

python_modules/dagster/dagster_tests/execution_tests/test_explicit_mode.py

@@ -0,0 +1,48 @@
+from contextlib import contextmanager
+from typing import Iterator
+
+import pytest
+from dagster import OpExecutionContext, Out, asset, multi_asset, op
+from dagster._core.definitions.asset_spec import AssetSpec
+from dagster._core.definitions.events import Output
+from dagster._core.definitions.materialize import materialize
+from dagster._core.errors import DagsterInvariantViolationError
+from dagster._utils.test import wrap_op_in_graph_and_execute
+
+
+@contextmanager
+def raises_missing_output_error() -> Iterator[None]:
+    with pytest.raises(
+        DagsterInvariantViolationError, match="did not yield or return expected outputs"
+    ):
+        yield
+
+
+def test_explicit_mode_op():
+    @op(out={"a": Out(int), "b": Out(int)})
+    def explicit_mode_op(context: OpExecutionContext):
+        context.set_explicit_mode()
+
+    with raises_missing_output_error():
+        wrap_op_in_graph_and_execute(explicit_mode_op)
+
+
+def test_explicit_mode_asset():
+    @asset
+    def explicit_mode_asset(context: OpExecutionContext):
+        context.set_explicit_mode()
+        pass
+
+    with raises_missing_output_error():
+        materialize([explicit_mode_asset])
+
+
+def test_explicit_mode_multi_asset():
+    @multi_asset(specs=[AssetSpec("foo"), AssetSpec("bar")])
+    def explicit_mode_multi_asset(context: OpExecutionContext):
+        context.set_explicit_mode()
+        yield Output(None, output_name="foo")
+        pass
+
+    with raises_missing_output_error():
+        materialize([explicit_mode_multi_asset])