Fixes #447: throw an error when printing output code in eager mode

helion/exc.py

@@ -382,6 +382,10 @@ class GraphModuleUnsupportedOps(BaseError):
     message = "GraphModule contains unsupported operations: {0}. Only pure computation graphs are supported (no load_attr or call_module ops)."
 
 
+class RefEagerModeCodePrintError(BaseError):
+    message = "No generated code to print out if ref eager mode is enabled."
+
+
 class NoDeviceLoopsInKernel(BaseError):
     message = (
         "Kernel contains no device loops. Add an hl.tile(...) or hl.grid(...) loop "

helion/runtime/settings.py

@@ -128,11 +128,14 @@ def __init__(self, **settings: object) -> None:
         Args:
             settings: Keyword arguments representing various settings.
         """
+
         if defaults := getattr(_tls, "default_settings", None):
             settings = {**defaults.to_dict(), **settings}
 
         super().__init__(**settings)  # pyright: ignore[reportArgumentType]
 
+        self._check_ref_eager_mode_before_print_output_code()
+
     def to_dict(self) -> dict[str, object]:
         """
         Convert the Settings object to a dictionary.
@@ -162,6 +165,13 @@ def check_autotuning_disabled(self) -> None:
         if msg:
             raise exc.AutotuningDisallowedInEnvironment(msg)
 
+    def _check_ref_eager_mode_before_print_output_code(self) -> None:
+        """
+        Check if ref eager mode is enabled before printing output code. If ref eager mode is enabled, raise an error.
+        """
+        if self.ref_mode == RefMode.EAGER and self.print_output_code:
+            raise exc.RefEagerModeCodePrintError
+
     @staticmethod
     def default() -> Settings:
         """

test/test_print_ref_eager_mode.py

@@ -0,0 +1,76 @@
+from __future__ import annotations
+
+import contextlib
+import io
+import unittest
+
+import pytest
+import torch
+
+import helion
+from helion import exc
+from helion._testing import TestCase
+import helion.language as hl
+
+
+class TestPrintOutputCode(TestCase):
+    def test_ref_eager_mode_code_print_error(self):
+        """Test that RefEagerModeCodePrintError is raised when using @helion.kernel with both settings"""
+
+        with pytest.raises(exc.RefEagerModeCodePrintError):
+
+            @helion.kernel(
+                use_default_config=True,
+                print_output_code=True,
+                ref_mode=helion.RefMode.EAGER,
+            )
+            def add(x: torch.Tensor, y: torch.Tensor) -> torch.Tensor:
+                x, y = torch.broadcast_tensors(x, y)
+                out = torch.empty(
+                    x.shape,
+                    dtype=torch.promote_types(x.dtype, y.dtype),
+                    device=x.device,
+                )
+                for tile in hl.tile(out.size()):
+                    out[tile] = x[tile] + y[tile]
+                return out
+
+            x = torch.randn([512, 512], device="cuda", dtype=torch.float16)
+            y = torch.randn([512, 512], device="cuda", dtype=torch.float16)
+            torch.testing.assert_close(add(x, y), torch.add(x, y))
+
+    def test_normal_mode_code_print(self):
+        """Test that output code is in stderr when using @helion.kernel with normal mode"""
+
+        f = io.StringIO()
+        with contextlib.redirect_stderr(f):
+
+            @helion.kernel(
+                use_default_config=True,
+                print_output_code=True,
+                ref_mode=helion.RefMode.OFF,
+            )
+            def add(x: torch.Tensor, y: torch.Tensor) -> torch.Tensor:
+                x, y = torch.broadcast_tensors(x, y)
+                out = torch.empty(
+                    x.shape,
+                    dtype=torch.promote_types(x.dtype, y.dtype),
+                    device=x.device,
+                )
+                for tile in hl.tile(out.size()):
+                    out[tile] = x[tile] + y[tile]
+                return out
+
+            x = torch.randn([512, 512], device="cuda", dtype=torch.float16)
+            y = torch.randn([512, 512], device="cuda", dtype=torch.float16)
+            torch.testing.assert_close(add(x, y), torch.add(x, y))
+
+        self.assertNotEqual(
+            f.getvalue(),
+            "",
+            "Output code in stderr should not be empty at normal mode.",
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()